Glossary
A – B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S – T – U – V – W – X – Y – Z
– 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
– 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
– 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
– 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
– 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
– 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)
– 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
– 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
– 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
– 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
– 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
– 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
– 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
– 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
– 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
– 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
– t –
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
– u –
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
– w –
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
– x –
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