– a –

abiotic: nonliving; plant diseases can be caused by a large array of abiotic factors such as nutrient deficiencies and water or temperature stress; abiotic agents cause noninfectious diseases

acaricides: pesticides used to control mites, ticks, and spiders

acclimatization: gradually reducing the light levels to which a plant is exposed

acuminate: a leaf blade tapering to a long, narrow point

acute: a leaf blade ending in an acute angle with a sharp, but not acuminate, point

adventitious: buds buds that arise at sites other than the stem apex or leaf axil; adventitious buds may develop at stem internodes, at the edge of leaf blades, from callus tissue at the cut end of stems or roots, or in a plant’s root system

aeration: the process by which the oxygen-deficient air in compost is replaced by air from the atmosphere; aeration can be enhanced by turning compost

aerobic: an adjective describing an organism that can live only in the presence of oxygen gas

aggregate: fruits fruits that come from a single flower which has many ovaries; the flower appears as a simple flower, with one corolla, one calyx, and one stem, but with many pistils and many ovaries; the ovaries are fertilized separately and independently; raspberries, blackberries, and strawberries are examples of aggregate fruits.

alternate: leaf arrangement an arrangement of leaves in alternate step along the stem with only one leaf at each node; also called spiral leaf arrangement

amendment, soil: see soil amendment

anaerobic: an adjective describing an organism that can live or function in the absence of air or free oxygen

angiosperms: plants that produce flowers and develop fruits that contain seeds; this group of plants can be divided into monocotyledons and dicotyledons

anions: negatively charged ions

annual: a flowering plant that passes through its entire life cycle from seed germination to seed production in one growing season and then dies; examples include marigold, zinnia, calendula, cucumber, and tomato

anther: a pollen sac in the stamen that is on top of a threadlike filament

antidesiccants: pesticides used to protect plants from winter damage, drought, windburn, and transplant shock

antitranspirants: pesticides used to reduce water loss from plants

asexual propagation: taking a part of one parent plant and causing it to regenerate into a new plant that is genetically identical to its one parent; asexual propagation involves the vegetative parts of a plant: stems, roots, or leaves; the major methods of asexual propagation are cuttings, layering, division, budding, and grafting

attractants: pesticides used to lure pests

avicides: pesticides used to control birds

axillary buds: lateral buds that arise in leaf axils

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– b –

bacteria: a group of microorganisms having single-celled or noncellular bodies; some bacteria provide a gummy substance that binds soil particles together

bactericides: pesticides used to control bacteria

bacterium: a single-celled microscopic organism with cell walls and no chlorophyll; a bacterium reproduces by fission

balled and burlapped plants: plants that are likely to have been grown in nursery rows for some time and to have been root-pruned so that the root system within the balls is compact and fibrous

banding: applying a pesticide to a strip over or along each crop row

bare-rooted plants: plants that have had the soil washed or shaken from their roots after digging; nearly all bare-rooted plants selected for transplanting in the garden are deciduous plants which are dormant

base saturation: a measure or the percentage of the cec sites which are occupied by basic cations such as calcium, magnesium, potassium, and sodium

biennial: a plant that starts from seed and produces vegetative structures (usually only foliage) and food storage organs (roots) the first season; in the second season, flowers, fruit, and seeds develop to complete the life cycle, and the plant dies; carrots, beets, cabbage, celery, onion, hollyhocks, foxglove, and sweet William are all biennials

binomial nomenclature: a system of plant classification based on the flowers or reproductive parts of a plant; the system was developed in the 18th century by Carl Linnaeus and assigns each plant a unique double Latin name called its genus (generic name) and species (specific name)

biotic: living; plant diseases are caused by a large array of biotic agents such as fungi, nematodes, bacteria, and viruses; biotic agents cause infectious diseases

blade: the expanded, thin structure of a leaf on either side of the midrib, or main vein; the blade is usually the large and most conspicuous part of a leaf

blights: sudden, often widespread death of twigs, foliage, or flowers

bolting: a phenomenon in which plants botanically classified as biennials may, in some cases, complete their life cycle in only one growing season; this situation occurs when drought, variations in temperature, or other climatic conditions cause the plant to physiologically pass through the equivalent of two growing seasons in a single growing season

brambles: thorny, perennial plants (e.g., blackberry, raspberry) that bear on biennial canes

bracts: showy, brightly colored specialized leaves (on such plants as dogwoods and poinsettias) that are often mistaken for flower petals

branch: a stem that is more than one year old

broadcasting: uniformly applying a pesticide to an entire, specific area by scattering

broad-leaved evergreens: landscape plants that have broad or wide leaves that remain green throughout the year (e.g.., boxwood, rhododendron, holly); broad-leaved evergreens provide structure in the winter garden and are often used for foundation planting

“browns”: in composting, woody, carbon-rich materials, such as corn stalks, leaves, straw, paper, sawdust, and wood chips; carbonaceous materials provide energy for microorganisms in compost piles

bud: an undeveloped shoot from which embryonic leaves or flower parts arise

budding or bud grafting: a method of asexual propagation uniting one bud and a small piece of bark from the scion with a rootstock; three methods of bud grafting are patch budding, chip budding, and t-budding; budding is a technique used to propagate cultivars that will not root well as cuttings or whose own root systems are inadequate

bulb: a shortened, compressed, underground stem surrounded by fleshy scales that envelop a central bud located a the tip of the stem; lilies, daffodils, tulips, and onions are bulbs

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– c –

calyx: a flower part divided into sepals

cane: a step

cankers: dead places on bark and the cortex stems; these areas are often discolored and raised or sunken

carbon: nitrogen ratio: the ratio of the weight of organic carbon (c) to that of total nitrogen (n) in an organic material; in composting, the proportion of these two elements should approximate 30 parts carbon to 1 part nitrogen by weight

cation exchange: the ability of a soil to trade one cation (positively charge ion) for another, either between soil particles or between soil particles and the soil solution

cation exchange capacity: cec; a measure of the soil’s ability to absorb (attach to the surface) cations and then release them to the soil solution or to plant roots; the cec of a soil is related to the amount of clay mineral and the amount of organic matter in the soil

cations: positively charged ions

chelates: chemical claws that help hold metal ions, such as iron, in solution, so that the plant can absorb them

chloroplasts: plant cells that contain the green pigment chlorophyll which traps the light energy in the process of photosynthesis

chlorosis: yellowing

clay: the finest soil particles; clay particles can be seen only with the aid of an electron microscope; clay particles feel extremely smooth when dry and become slick and sticky when wet

cleft: leaf margins having incisions that extend more than halfway to the midrib

cold frame: a low structure covered with glass or plastic “lights” used primarily to protect transplants from early spring freezes and to harden or hold transplants

companion planting: the practice of placing plants in close proximity to each other based on the beneficial effects this will have; some research indicates that companion planting may attract beneficial insects by providing hiding places or food sources for the insects; certain plants may also lure insect pests away from other plants or confuse a pest with their scent

complete fertilizer: a fertilizer that contains nitrogen, phosphorous, and potassium

complete flower: flowers that have a stamen, pistils, petals, and sepals

composite: see head

compost: a group of organic residues, or a mixture of organic residues and soil, that have been piled, moistened, and allowed to undergo biological decomposition

composting: the biological breakdown or organic matter by a managed process

compound leaves: leaves having several separate blades, called leaflets, arising from the same petiole

conifers: cone-bearing plants, generally with narrow-leafed or needle-type foliage

conks: fungal fruiting structures formed on rotting woody plants (shelf or bracket fungi)

contact poisons: pesticides that kill pests simply by touching them

container-grown plants: plants usually grown in the container in which they are sold

cordate: a heart-shaped leaf blade

corm: a solid, swollen stem whose scales have been reduced to a dry, leaf-like covering; it is similar to a bulb but does not have fleshy scales; gladiolus and crocus are corms

corolla: a flower part divided into petals

cortex: cells that move water from the epidermis into the middle of the root

corymb: a type of inflorescence in which the florets are on stalks, called pedicels, and are arranged at random along the peduncle in such a way that the florets create a flat, round top; an example is yarrow

cotyledons: modified leaves found on embryonic plants in seeds; also called seed leaves

cover crop: or green manure; a crop of sown for the purpose of being turned under to enrich the soil; a cover crop also prevents weed seeds from taking root and soil from eroding

crenate: leaf margins having rounded teeth

crop rotation: the practice of moving a vegetable crop to a different location in the garden from year to year; crop rotation limits the effect of disease organisms on plants by not allowing them to build up in the soil and reduces the number of insect pests that overwinter near a host plant

crown: a region of compressed stem tissue from which new shoots are produced, generally found near the surface of the soil; crowns are found on many herbaceous perennials

cross-pollination: a process that combines genetic materials from one plant to produce stronger seed and more vigorous offspring; more plants reproduce by cross-pollination than self-pollination

cultivar: or variety; a group of plants that have the same characteristics (such as color, height, and flavor) that they retain even when reproduced

cuticle: a covering on the epidermis of a leaf blade that is composed of a waxy substance called cutin; the cuticle protects the leaf from dehydration and prevents penetration of some diseases

cutin: a waxy substance composing the cuticle of a leaf blade

cutting: a vegetative plant part which is severed from the parent plant in order to regenerate itself and form a whole new plant; cutting may be stem cuttings, leaf cuttings, or root cuttings

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– d –

damping off: disease the wilting and early death of young seedlings caused by a variety of pathogens

day-neutral plants: plants that form flowers regardless of day length

deadheading: the removal of spent flowers to maintain vigorous growth and to keep flower borders looking neat

deciduous shrubs: shrubs that loose their leaves in fall, deciduous shrubs give seasonal color and texture to the landscape; their flowers, foliage, fruit, and bark provide color and landscape interest

dentate: leaf margins having teeth ending in an acute angle pointing outward

dessicants/ defoliants: pesticides used to remove or kill leaves and stem

dessication: drying out of plants

dicotyledon: or dicot; an angiosperm that produces two seed leaves (cotyledons), has flower parts in multiples of four or five, and has variously shaped leaves with netted veins

dioecious plants: plants in which pistillate and staminate flowers occur on separate plants; examples are holly and yew

dipping: immersing a plant in a pesticide

directing: aiming a pesticide at a portion of a plant, animal, or structure

disease: when a host plant responds to the presence of a pathogen; the host’s response usually results in the development of symptoms of the disease, such as blight, spots, or necrosis

disbudding: removal of small side buds to allow a plant to concentrate its energy on producing one or a few large blooms

division: a method of asexual propagation in which a plant with more than one rooted crown is divided and the crowns planted separately

drenching: saturating the soil with a pesticide

dripline: a line on the ground defined by the outer edge of a plant’s branches

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– e –

elliptical: a leaf blade two to three times longer than wide

embryo: the part of a seed that is a miniature plant in an arrested state or development

endosperm: the built-in food supply contained in most seeds

entire: smooth leaf margins with no teeth or notches

epidermis: a layer of protective cells on the top and bottom of a leaf blade

etoliation: a situation in which too little light results in a long internode, creating a “spindly” plant

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– f –

f1 hybrid: the first generation offspring from two distinct, purebred plants; these plants are vigorous in growth and uniform in appearance; f1 stands for fist filial

fertilizers: materials containing plant nutrients that are added to the environment around the plant; generally, they are added to the water or soil, but some can also be added to the air or sprayed on the leaves; fertilizer is not plant food

fertilization: the process of supplying the basic chemical elements to the environment around the plant

fibrous root system: a root system that develops on plants whose primary root ceases to elongate, leading to the development of numerous secondary roots, which branch repeatedly and form a wide-spreading root system; most herbaceous monocots (like grasses) have fibrous root systems

filament: a threadlike structure that supports the anther in the stamen; the filament holds the anther in position so the pollen it contains may be dispersed by wind or carried to the stigma by insects or other pollinators

floating row cover: a row cover made of breathable, lightweight material that can be laid directly on top of many crops without any supports

flower: the part of a plant important in sexual reproduction; a flower is generally the showiest part of a plant

foliar: application applying a fertilizer or pesticide to the leaves of plants

friable soil: a soil that will form a ball when squeezed but will crumble when handled

fumigants: gasses which kill when they are inhaled or otherwise absorbed by pests

fungicides: pesticides used to control fungi

fungus: an organism with no chlorophyll that reproduces by means of structures called spores and usually has filamentous growth (mold, yeast, mushroom)

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– g –

galls: abnormal, localized swellings on leaf, stem, or root tissue

genus: see binomial nomenclature

germination: the growth process of a plant that begins when a seed absorbs water through the seed coat and ends when the green plant begins photosynthesis; successful germination requires the proper environmental conditions; favorable temperatures, correct light levels, and adequate moisture and aeration

gradual renewal pruning: pruning in which a few of the oldest and tallest branches are removed at or slightly above ground level on an annual basis to rejuvenate a plant

grafting: a method of asexual propagation in which plant parts are joined so they will grow as one plant; this technique is used to propagate cultivars that will not root well as cuttings or whose own root systems are inadequate; types of grafting include cleft grafting, bark grafting, and whip or tongue grafting

green manure: see cover crop

“greens”: in composting, nitrogen-rich materials, such as food scraps, grass clippings, and rotten manure; microorganisms in compost piles ingest nitrogenous materials for protein synthesis

ground covers: low-growing plants that spread quickly to form a dense cover

growth regulators: pesticides used to stop, speed up, or otherwise change normal plant or insect processes

guard cells: pairs of epidermal cells on the undersides of leaves that surround of leaves that surround openings to the interior of the leaf; guard cells regulate the passage of water, oxygen, and carbon dioxide through the leaf

gymnosperms: plants that do not have true flowers, although they produce seeds, the seeds are not enclosed in fruits; examples are pine, spruce, cedar, juniper, and gingko

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– h –

hairs: an extension of the epidermal cells on the leaves of some plants such as African violets

half-hardy annual: an annual that can withstand light frosts but not heavy frosts or freezing

hardening: the process of altering the quality of plant growth to withstand the change in environmental conditions which occurs when plants are transferred from a greenhouse or home to the garden; hardening can be accomplished by gradually lowering temperatures and relative humidity and reducing water; this procedure promotes firmer, harder growth in plants

hardiness: a plant’s ability to withstand winter and summer climatic changes, which will determine its longevity or appearance

hardiness zone: one of eleven zones on the united states department of agriculture’s hardiness zone map; the zones are based on a range of an area’s average annual low temperature and help gardeners select plants that can survive winters in their area

hardy annual: an annual that can withstand frosts in spring and fall; it may need protection from heavy frosts or freezing

head: or composite; a type of inflorescence composed of two distinct types of stemless florets; usually, fertile disk florets crown the central button are surrounded by generally sterile, strap-like ray florets, often wrongly referred to as “petals”

heading cuts: pruning cuts involving cutting back branches to just above good buds; heading cuts increase the number of new shoots, stiffen branches and hold them in place, stimulate branching, make plants shorter and more dense, redirect growth of alternate-leafed plants, and give more compact, dense shape to opposite-leafed plants

hedge: plant material set in a row so as to merge into a solid, linear mass; hedges serve as screens, fences, walls, and edgings, and may be deciduous or evergreen

herb: a plant valued for flavoring food, for medicinal purposes, or for its fragrance; it is an annual, biennial, or perennial plant; culinary herbs (e.g., rosemary, parsley, basil) are used for food preparation, medicinal herbs (e.g., pennyroyal, horehound) have been credited with curative powers, and aromatic herbs (lavender, lemon verbena) are pleasantly scented

herbaceous perennial: a perennial whose top dies back to the ground each winter and new stems grow from the roots each spring; most flower garden perennials are herbaceous

herbicides: pesticides used to control plants

host: a living organism used as a food source by a parasite; hosts are usually larger and stronger than the parasites and not killed promptly; some continue to live in close association with the parasite rather than be killed

hot bed: a cold frame with supplemental heating provided by a deep layer of fresh manure or by electricity

humus: vegetable and animal matter that has been modified from the original tissue through decomposition; it is the ultimate end product formed by the decay and oxidation of organic matter by the soil organisms

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– i –

imperfect flowers: flowers lacking either stamens or pistils

incised: leaf margins having sharp, deep irregular teeth or incisions

incomplete fertilizer: a fertilizer lacking one of the major components (nitrogen, phosphorus, or potassium)

incomplete flower: flowers lacking any of these flower parts: stamen, pistil, petals, or sepals

infection: when a pathogen invades plant tissue and establishes a parasitic relationship between itself and the host

inflorescence: a cluster of flowers and how they are arranged on a floral stem; some examples of inflorescence are spike, raceme, corymb, umbel, and head

in-furrow application: applying a pesticide to or in the furrow in which a plant is growing

inoculation: the introduction of a pathogen to host plant tissue; pathogens can be introduced to a host plant by wind, rain, running water, birds, insects, people, or equipment; some pathogens move themselves short distances

inoculant: the dried or inactive microorganisms that become active when added to the compost pile

inoculum: any part of a pathogen that comes in contact with a host plant

insecticides: pesticides used to control insects

internode: the region between two nodes on a stem of a plant

interplanting: growing two or more types of vegetables in the same place at the same time

interveinal chlorosis: yellowing between the veins of leaves

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– l –

lanceolate: a leaf blade longer than it is wide

landscape design: the art of organizing and enriching outdoor space through the arrangement of plants, structures, and land form n agreeable and useful relationship with the natural environment and the desired use

lateral buds: buds located on the sides of the stem of a plant; most lateral buds arise in leaf axils and are called axillary buds

layering: a propagation technique used for hard-to-root plants; the basic principle of layering is to produce roots on a stem that is still attached to the parent plant

leaf: a plant part whose primary function is to photosynthesize, or capture energy from the sun and convert it to sugars for later use; leaves contain chlorophyll and are generally broad to intercept a maximum amount of sunlight

leaf apex: the leaf tip

leaf axil: the small angle formed between the petiole of a leaf and a stem

leaf base: the point where the leaf joins to a petiole

light duration: the amount of time per day that a plant is exposed to sunlight; light duration is also called photoperiod

light quality: the color or wavelength of light reaching plant surfaces

light quantity: the intensity or concentration of light reaching a plant

linear: a narrow leaf blade

loam: a textural class of soil that has moderate amounts of sand, silt, and clay

lobed: leaf margins having incisions that extend less than halfway to the midrib

long-day plants: or short-night plants; plats that form flowers only when day lengths exceed twelve hours; long-day plants include many summer-flowering plants, such as rudbeckia and California poppy, as well as many vegetables including, beet, radish, lettuce, spinach, and potato

long season plants: plants that are slow to mature

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– m –

macro-nutrients: the six elements (nitrogen, potassium, magnesium, calcium, phosphorous, and sulfur) found in soil and used in relatively large amounts by plants

marginal burn: browning of leaf edges

maturation zone: an area of the root in which cells change into specific tissues such as epidermis (outermost layer of cells surrounding the root responsible for taking up water minerals), cortex (cells that move water from the epidermis into the middle of the root), and vascular (located in the center of the root; conducts water and nutrients upward and synthates downward) tissue

meristem: or root tip; an area of the root that manufactures new cells; it is an area of cell division and growth

mesophyll: the middle layer of a leaf located between the upper and lower epidermis; this is the layer in which photosynthesis occurs; the mesophyll is divided into a dense upper layer called the palisade and a lower layer, called the spongy layer, that contains much air space; the cells in these two layers contain chloroplasts which are the actual site of the photosynthetic process

metamorphosis: a marked or abrupt change in form or structure; the term refers to an insect’s stages of development

micro-nutrients: or trace elements; the eight elements (iron, zinc, molybdenum, manganese, boron, copper, cobalt, and chlorine) found in soil and used by plants in much smaller amounts than the macro-nutrients

microorganism: an organism requiring magnification for observation

midrib: the main vein of a leaf

miticides: pesticides used to control mites

modified stem: a stem that is found either above or below ground; the above-ground modified stems are crowns, stolons, and spurs; below-ground stems include bulbs, corms, rhizomes, and tubers

molluscicides: pesticides used to control mollusks, such as slugs and snails

monocotyledon: or monocot; an angiosperm that produces one seed leaf (cotyledon), has flower parts in multiples of three, and has long, narrow leaves with parallel veins

monoecious plants: plants in which pistillate and staminate flowers occur on the same plant; examples are begonia and corn

muck: an accumulation of decaying or decayed vegetable matter; it may be entirely devoid of any mineral soil

mulch: a layer of organic (e.g.. shredded bark) or inorganic (e.g., gravel) material around plants that helps to conserve moisture, suppress weeds, stabilize soil temperatures, and provide an orderly appearance

multiple fruits: fruits derived from a tight cluster of separate, independent flowers borne on a single structure; each flower has its own calyx and corolla; examples of multiple fruits are pineapple, fig, and beet

mycelia: masses of fungal threads (hyphae) which composes the vegetative body of a fungus

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– n –

narrow leaf evergreens: ornamental plants that have long, slender leaves that remain green throughout the year (e.g., pine, fir, juniper, cedar); narrow leaf evergreens are used to screen out unsightly views and noise and to reduce the effects of sun and wind on buildings

necrosis: death of tissue

necrotic spots: dead spots on leaves

nematicides: pesticides used to control nematodes

nematode: a microscopic roundworm, usually living in soil, which feeds on plant cells

net-veined leaves: leaves having veins which branch from the main rib and subdivide into finer veinlets which spread in a complicated network; net-veined leaves occur in dicots and are also called reticulate-veined leaves

node: the region of a stem where leaves are attached

nonselective pesticides: pesticides that kill most plants or animals

nutrient-holding capacity: the ability to absorb and retain nutrients so they will be available to the roots of plants

nutrition: see plant nutrition

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– o –

obtuse: a leaf blade tapering to a rounded edge

ooze: or flux; viscid mass of juices composed of host and parasitic substances found exuding from some diseased plants

opposite leaf arrangement: an arrangement in which leaves are positioned across the stem from each other, two leaves at each node

organic fertilizer: fertilizers in which the nutrients are derived solely from the remains of by-products of a once-living organism; cottonseed meal, blood meal, and all manures are examples of organic fertilizers

ovary: a component of the pistil that contains the ovules, or eggs

ovate: an egg-shaped leaf blade

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– p –

parallel-veined leaves: leaves in which numerous veins run essentially parallel to each other, as in grasses, bananas, callas, and pickerel weed; all parallel-veined plants are monocots

parasitic seed plant: a higher plant with chlorophyll that lives parasitically on other plants (mistletoe, dodder)

parasites: living organisms that live on or in the bodies of living organisms (called the hosts) from which they get their food during at least one stage of their existence

parent material: the bottom soil horizon consisting of decomposed rock that has acquired some characteristics of the subsoil and retained some characteristics of the rock from which it weathered

pathogen: an organism capable of infecting a plant with a disease

pedicel: a small stem or stalk to which a floret is attached in raceme, corymb, and umbel types of inflorescence

peduncle: the stem of a flower cluster or of a solitary flower

penetration: the active or passive process of a pathogen getting inside a host plant

perennial: a plant that lives for three or more years; once it reaches maturity, it generally produces flowers and seeds each year

perfect flowers: flowers that have functional stamens and pistils

perianth: the part of a flower composted of the calyx and the corolla

perlite: a sterile, lightweight, porous, white material produced by heating volcanic rock to approximately 1800 degrees f.; perlite’s principal value in soil mixtures is aeration

petals: the division of a flower corolla; petals are often highly colored; the shape, arrangement, and number of flower petals are useful in identifying plants; flowers of dicots have petals in multiples of four or five, and monocot flowers have petals in multiples of three

petiole: the stalk which supports the leaf blade; the base of the petiole is attached to the stem at a node

pH: see soil pH

phloem: one of two types of complex tissue composing the vascular system of the stem of a plant; phloem conducts synthates manufactured in the plant to wherever they are needed

photoperiod: see light duration

photosynthesis: the process by which plants internally manufacture their own food using chlorophyll, energy from light, carbon dioxide from the air, and water from the soil

phytoplasma: a microscopic, bacteria-like organism that lacks a cell wall and therefore appears filamentous

pinching: removing the main growing point on some annuals and perennials to develop multiple stems for more lateral branches

piscicides: pesticides used to control fish

pistil: the female part of the plant, it is the center of the flower and consists of the stigma, style, and ovary

pistillate flowers: flowers possessing a functional pistil but lacking stamens; also called female flowers

pith: the central region of many woody stems

plant disease: sign the visible presence of a pathogen, such as a fungal fruiting body or bacterial discharge associated with the disease

plant disease symptom: the physical expression of disease by a plant; examples of symptoms are

plant disease syndrome: the group of signs and symptoms which collectively characterize a disease

plant nutrition: the needs and uses of the basic chemical elements in the plant

plastic soil: a soil high in silt or clay particles that would tend to remain stuck together

plumule: the part of a seed embryo that grows upward to develop into the stem and leaves of a plant

pollination: the transfer of pollen from an anther to a stigma; pollination may occur by wind or ran, or by pollinators such as bats, birds, and insects

post-emergent pesticide: a pesticide used after a crop or weeds have germinated

predators: insects (or other animals) that catch and devour other creatures (called the prey), usually killing and consuming them in a single meal; the prey is generally smaller and weaker than the predator

predacides: pesticides used to control pest animals

pre-emergent pesticide: a pesticide used before plants emerge from soil

pregermination: a seed-starting method in which seeds are sprouted before they are planted in pots or in a garden; this procedure reduces the time to germination and ensures a high percentage of germination since environmental factors are optimum

pre-plant pesticide: a pesticide applied to the soil before a crop is planted

propagation: the process of multiplying the numbers of a species of a plant, perpetuating a species, or maintaining the youthfulness of a plant; there are two type of propagation, sexual and asexual

pruning: removing plant material in order to train a plant, maintain plant health, improve the quality of flowers, fruit, foliage, or stems, or restrict growth

pycnidia: minute, fungal, asexual fruiting structures, usually globose and black, formed on plant surfaces

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– r –

raceme: a type of inflorescence in which the florets are on small stems (pedicels) attached to an elongated flower stem; an example is a snapdragon

radicle: a seedling embryo root; the radicle develops into one or two major types of root systems; taproot or fibrous

relative humidity: the percentage of water vapor in the air compared to the total amount of water the air could hold at a given temperature and pressure

repellents: pesticides used to keep pests away

reproductive parts of plants: those parts involved in the production of seed; flower buds, flowers, fruits, and seed

respiration: the process by which sugars and starches are slowly oxidized in plants to release energy

reticulate-veined leases: see net-veined leaves

rhizome: a specialized stem which grows horizontally at our just below the solid surface; some rhizomes are compressed and fleshy (iris), and others are slender and elongated (quackgrass)

rhizomorphs: string-like strands of fungal mycelia sometimes found under the bark of trees

rodenticides: pesticides used to control rodents

root cap: an area outside the very tip of the root that consists of cells that are sloughed off as the root grows through the soil; the root cap covers and protects the meristem (root tip)

root pruning: the practice of digging a trench around a tree or shrub in order to concentrate its root growth in the soil below the top part of the plant; root pruning makes it easier for a tree or shrub to be transplanted

root tip: see meristem

roots: plant parts forming the below-ground portion of a plant; the principal functions of roots are to absorb nutrients and water, to anchor the plant in the soil, to furnish physical support for the stem, and to serve as food storage organs; in some plants, roots are used for propagation

rootstock: or stock; existing plant material that provides a new plant’s root system and sometimes the lower part of the stem in grafting or budding

rosulate: leaf arrangement an arrangement in which the basal leaves form a rosette around the stem with extremely short nodes

rots: general decomposition and destruction of tissue

row covers: blanket-like sheets of material, (solid, slitted, or perforated plastic or “breathable” spunbonded or woven polyester) used primarily to enhance crop growth; row covers require hoops or other supports to keep their weight off a crop

runner: a specialized stem at the soil surface that forms a new plant at one or more of its nodes; also called a stolon

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– s –

sagittate: an arrowhead-shaped leaf blade with two pointed lower lobes

sand: the coarser mineral particles of soil; most sand particles can be seen without a magnifying glass and feel rough when rubbed between the thumb and the forefinger

scale leaves: leaves found on rhizomes; also, the small. leathery protective leaves which enclose and protect buds

scarification: see seed scarification

scion: the portion of a cultivar that is to be propagated through grafting or budding

seed coat: the hard outer covering which protects a seed from disease and insects and prevents water entering the seed

seed scarification: a treatment that involves breaking, scratching, or softening the seed coat so that water can enter and begin the germination process

seed stratification: a treatment that involves artificially chilling seeds so they may germinate

seeds: mature ovules

selective pesticides: pesticides that kill only certain kinds of plants or animals

self-fertile plants: single plants in which the pollen and ovules can unite to form seeds containing viable embryos

sepals: small, often green, leaf-like structures at the base of the flower; sepals protect the flower when in bud

serrate: leaf margins having small, sharp teeth pointing toward the apex

sessile: a leaf that is attached directly to a stem; a petiole is absent in this type of leaf

sexual propagation: the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual; sexual propagation involves the floral parts of a plant

short-day plants: or long-night plants; plants that form flowers only when the day length is less than critical length, generally about twelve hours; short-day plants include many spring- and fall-flowering plants such as chrysanthemums and poinsettias

short season plants: plants that are quick to mature

shrub: a perennial woody plant with one or more main stems, generally less than 25 feet tall at maturity

side-dressing: applying a fertilizer or pesticide along the side of a crop row

signal words: words on a pesticide label that tell how hazardous the product is to people: danger poison (highly toxic), warning (moderately toxic), and caution (low toxicity; relatively nontoxic)

silt: relatively fine soil particles that feel smooth and floury; silt particles are so fine that they cannot be seen by the unaided eye

simple fruits: fruits which develop from a single ovary; simple fruits include cherries and peaches (drupes), pears and apples (pomes), and tomatoes (berries)

simple leaves: leaves having one single blade

sinuate: leaf margins having a pronounced sinuous or wavy margin

soil: weathered rock fragments and decaying remains of plants and animals (organic matter); it contains varying amounts of air, water, and microorganisms and furnishes mechanical support and nutrients for growing plants

soil amendment: any addition to the soil which improves its physical or chemical condition; common soil amendments include lime and sulphur to change soil pH, greensand to improve potassium levels, and organic matter, such as manures, leafmold, and compost, to improve soil qualities

soil conditioner: a soil additive that stabilizes the soil, improves its resistance to erosion, increases its permeability to air and water, improves its texture and resistance of its surface to crusting, makes it easier to cultivate, or otherwise improves its quality

soil consistency: the tendency of the soil to crumble or to stick together when moist; a soil consistency can be either friable or plastic

soil drainage: the rate and extent of water movement in the soil, both across the surface as well as downward through the soil

soil pH: a measure of the amount of hydrogen in soil taken from a scale that measures the hydrogen (acid forming) ion activity of soil or growth media

soil porosity: the number, size, and formation of the open spaces in the soil; soil porosity is related to the number and size of air spaces in the soil and depends on the size and arrangement of the individual soil particles present

soil profile: a collective term for the principal soil horizons (surface soil, subsurface soil, and subsoil)

soil structure: the combination or arrangement of primary soil particles into secondary particles, units, or peds

soil texture: the relative amounts of differently sized soil particles, or the fineness/coarseness of the mineral particles in the soil; soil texture depends on the relative amounts of sand, silt, and clay

soilless mix: a germination medium consisting of sphagnum peat moss and vermiculite

solitary flowers: flowers having only one flower per stem

soluble salts: minerals, like fertilizers, dissolved in water; when water evaporates from the soil, the salts stay behind; as the salts in the soil become more and more concentrated, plants find it harder and harder to take up water; signs of high soluble salts include reduced growth, brown leaf tips, dropping of lower leaves, small new growth, dead root tips, and wilting

species: see binomial nomenclature

spike: a type of inflorescence in which each of many stemless florets is attached to an elongated flower stem; an example is gladiolus

spines: specially modified leaves which protect he plant, as on the barberry

spiral: leaf arrangement see alternate leaf arrangement

spot treatment: applying a pesticide to a small section or area of a crop

spots: circular or irregular lesions on above-ground tissue

spur: a short, stubby, side stem that arises from the main stem; spurs are common on fruit trees, such as pears, apples, and cherries, where they may bear fruit; if sever pruning is done close to fruit-bearing spurs, the spurs can develop into long, non-fruiting stems

stamen: the male reproductive organ of a plant

staminate flowers: flowers having stamens but no pistils; also called male flowers

stem: the main axis of a plant; stems generally extend upward and often produce secondary stems called branches; in some plants, stems are horizontal at ground level, and some plants even produce underground stems; all stems have nodes and internodes; stems give plant their characteristic form, support buds and leaves, and serve as conduits for carrying water, minerals, and sugar

stem cuttings: above-ground stems that are divided into sections with internodes and nodes; these sections produce roots to form a new plant when treated properly

stigma: a sticky structure located at the top of the pistil that receives pollen during pollination

stock: see rootstock

stolon: see runner

stomach poisons: pesticides that kill when swallowed

stomates: openings on the undersides of leaves which through which water, oxygen, and carbon dioxide are regulated by guard cells

storage leaves: leaves found in bulbs and succulents that serve as food storage organs

stratification: see seed stratification

style: a tube like structure on the pistil that transports pollen from the stigma to the ovary

subirrigation: watering plants from below

subsoil: the soil layer that supports the surface soil and acts as the soil reservoir, providing storage space for water and nutrients for plants, aiding in temperature regulation of the soil, and supplying air for the roots or plants; the subsoil layer is usually finer and firmer than the surface soil and has a much lower organic matter content than the surface soil

surface soil: a course soil layer that contains more organic matter than any other soil layer; it is usually the most fertile soil layer and has the greatest concentration of plant roots of any soil horizon; plants obtain much of their nutrients and water from the surface soil

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taxonomy: plant classification

tender annual: an annual whose plant tissue is seriously damaged by frost

tendrils: specially modified leaves which assist in supporting the stems, as on peas

thatch: dead and drying grass plant parts (such as roots, stems, and shoots) that accumulated above the soil surface of a lawn

thermoperiod: daily temperature change

thinning cuts: pruning cuts involving the complete removal of branches back to a main stem or trunk; thinning cuts reduce the number of new shoots, direct growth, inhibit branching, and allow remaining limbs to grow longer

tilth: the physical or mechanical conditioning of the soil to render it more suitable for gas exchange and moisture movement needed for good plant growth

topdressing: applying a layer of compost, or other material, to the surface of a lawn

trace elements: see micro-nutrients

translocated herbicides: herbicides that move from the point of initial application to circulate throughout the plant; the circulation of the toxin ensures the killing of the entire plant

transpiration: evaporation of water from the leaves’ stomates

tree: a perennial woody plant, generally with one main stem called a truck, and generally over 25 feet tall at maturity

truncate: a leaf blade having a relatively square end

tuber: an enlarged portion of an underground stem; like any other stem, a tuber has nodes that produce buds

tuberous roots: underground storage organs that are true roots, not stems, and have neither nods or internodes; dahlias and sweet potatoes produce tuberous roots

turgor: the firmness of plant tissue maintained by water

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umbel: a type of inflorescence in which the pedicels all arise from one point on the peduncles; an example is dill

– v –

variety: see cultivar

vascular cambium: a thin band of cells separating the bands of xylem and phloem in older dicot stems; this is a lateral meristem (site of cell division and active growth) and is responsible for the increase in stem girth in woody dicots

vascular plants: plants containing tissues which transport water and dissolved minerals

vector: an insect that carries pathogens from plant to plant (e.g., the elm bark beetle carries Dutch elm disease and various aphids carry virus disease

vegetative: parts of plants the stems, leaves, leaf buds, and roots

venation: the patterns in which veins are distributed in the blades of leaves; two principle types of venation are parallel-veined and net-veined

vermicomposting: the process by which worms convert organic waste into worm castings

vermiculite: a sterile, lightweight, mica-like natural rock that will hold large quantities of air, water, and nutrients needed for plant growth; vermiculite is a component of many artificial potting mixture

vertical gardening: the use of trellises, nets, strings, cages, or poles, to support growing plants

very hardy perennial: a perennial that can withstand winter extremes with only slight protection

very tender annual: an annual whose tissues will be destroyed by frost; it needs warm weather for growth

vine: an annual or perennial plant that develops long, trailing stems that grow along the ground unless they are supported by another plant or structure

viroid: a virus-like particle that lacks the outer protein coat of a virus particle

virus: a submicroscopic, subcellular particle consisting of nucleic acid and protein that requires a host cell in which to multiply

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whorled leaf arrangement: an arrangement of leaves in circles along the stem, with three or more leaves at each node

windbreak: a group of trees or shrubs to make a wind screen; windbreaks are highly effective because they break the force of the wind by absorbing it

wood: most of the girth of woody stems surrounding the pith; wood is composed of rings of dead xylem tissue

woody perennial: a perennial whose top growth persists and develops woody tissue; trees and shrubs are classified as woody perennials

worm castings: the dark, fertile, granular excrement of a worm; these granules are rich in plant nutrients

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xylem: one of two types of complex tissue composing the vascular system of the stem of a plant; xylem tissue conducts water and minerals up from the roots

– y –

yard waste: leaves, grass clippings, yard trimmings, and other organic garden debris

– z –

zone of elongation: an area of the root in which cells increase in size through food and water absorption; these cells, by increasing in size, push the roots through the soil

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