How to Grow Cranberries

Soil Conditions: Cranberry beds should be established on a base material which will retard vertical movement of water.  This will supply the so-called impermeable layer which will allow the bed to hold a flood for harvest, winter protection, etc.  Examples of base materials are peat, clay, and heavy packed topsoil (loam).  A minimum of four inches of sand should be applied above the base layer of the bed prior to planting.  Sand with at least a 60-70% coarse particle content is best.  Higher amounts of coarse particles were correlated with higher yields in Massachusetts research studies.  Most likely the benefit is in providing adequate drainage.  Proper drainage is essential for good root development and aeration as well as for the prevention of Phytophthora root rot.  Sand pH is also important.  It should range between 4.0 and 5.0 or you will have to add sulfur to adjust.  Get a sample tested for pH before planting.

Planting Density: You should plan to visit the site from where you want to buy your vine, sometime during the fall (prior to the year you intend to plant).  Ask for past production records to insure that you will be getting good vine.  Normally, vines are planted at the density of one ton per acre.  However, if planting is late (June or July) and/or growing conditions are severe, or if you want more rapid establishment, then a higher density (e.g. 1.5 to 2 tons per acre) may be warranted.  Unrooted cuttings are the standard planting material but rooted cuttings (plugs) or tissue culture plants have been used effectively.

Irrigation: New plantings should be irrigated to maintain moist but not saturated soil.  If you get consistent puddling, the bed is too wet!  Irrigate less or improve drainage.  Too much moisture can retard root growth, prevent roots from achieving proper depth, and in extreme cases, eventually kill the vines. Note: The frequent irrigation needed for new plantings can lead to a buildup of the fungi which cause fruit rot and other cranberry diseases.  High nitrogen doses may also contribute to increased incidence of fruit rot as the planting begins to produce. It is wise to begin using fungicides in the 2nd year to avoid inoculum buildup.  A Late-Water flood may also be useful in this regard: (Late-Water Flood (MS Word) | (Late-Water Flood (pdf).

Frost Protection: Use your sprinkler system during the appropriate hours [Table of Frost Tolerances] or flood the bed if running sprinklers is not an option.

Fertilizers: Avoid excess phosphorus (P) applications (use nitrogen alone for some applications). Acid soils bind large quantities of P which will not be available to the cranberry plants.  Alternate between applications of complete, and nitrogen-only fertilizers.

Fertilizing New Plantings – Year 1:

  • Phosphorus (at time of planting): Research indicates that the use of 100 lb/A of 0-46-0 increases growth of new vines (more ground covered). Apply 100 lb/A triple superphosphate (0-46-0) in either one of the following schedules: Schedule 1: 50 lb/A under the top 2-3 inches of sand, 50 lb/A on the surface after the vines are scattered but before disking in the vines. Schedule 2: Apply the fertilizer to the soil surface, then scatter and disk in the vines.
  • Nitrogen: Slow-release N applied at the time of planting (just after the vines have been set in) provides a sustained growth stimulation during stand establishment.  In addition to this application, follow a standard new planting fertilizer schedule, such as: Apply 50-200 lb/A slow-release N fertilizer. Use materials which are entirely slow-release based on the action of water and soil microbes [Examples: 31-0-0 IBDU or 40-0-0 Noram Blue Chip (MU)].
  • When Roots are Established and Growth Starts: Apply N now (5-10 lb/A nitrogen – urea types are recommended; ammonium sulfate may burn new roots). If no phosphorus was applied at planting, add P now (50 lb/A 0-46-0 – triple superphosphate only if none was used at planting!)
  • For the Remainder of Year 1: Fertilize every 2 to 3 weeks until mid-August.  Stop adding fertilizer by late summer to allow plants to harden off.  Otherwise, tender new growth could be damaged by low temperatures in the fall. Schedule: 5-10 lb/A nitrogen each application.  Alternate ammonium sulfate (21-0-0) or urea with complete NPK fertilizer (50-100 lb/A 10-20-20 or 12-24-12 or 14-14-14). Using only N all season leads to tender top growth susceptible to drought and to damage by cranberry tipworm.

Fertilizing New Plantings – Year 2:

Early in the Season: Begin to fertilize in late April when soil temperatures have begun to rise. SulPoMag or an equivalent may be used now – 100 to 200 lb/A.

  • Fertilize as at the end of Year 1, beginning in late April or early May.
  • Alternate 5-10 lb/A nitrogen alone with 5-10 lb/A nitrogen as NPK.
  • If fill-in and growth are good, begin to cut back on N at mid-season to encourage fruit production.
  • If fill-in and growth are poor, continue Year 1 schedule until mid-August.
  • As in Year 1, stop fertilizing in August to allow plants to harden for winter.

Fertilizing New Plantings – Year 3:

The bog should be well established and should have received a light sanding by now. The fertilizer schedule should begin to be like that for established beds.

See also:

If all has gone well, some crop should be harvested this fall (of Year 3).  Do not forget the fungicides, and consider using a Late-Water flood: (Late-Water Flood (MS Word) | (Late-Water Flood (pdf).

End Result: After one year, you should have foot-long runners and well-established roots (plants will become more tolerant of dry conditions). By the end of the second year, you should have good coverage with vines and you may need to apply a light sanding to anchor the runners.  Some fruit production should occur in year three with a fair to good crop in year four.  Once the bed is established, the average upright density should be about 600 uprights/sq. ft. for Early Black, and 400 uprights/sq. ft. for Howes. The normal total length for the new growth on an upright is 2 to 3.5 inches for Early Black and 2.5 to 4 inches for Howes, with 1.5 to 2 inches of leaves above the fruit on a flowering upright. Stevens should be about the same density and length as Howes but with more robust stems and larger leaves.  Most growers in Maine are growing primarily Stevens.

Sources:

  • Carolyn DeMoranville, 1995 Workshop, University of Massachusetts Cranberry Experiment Station. Adapted for Maine by David Yarborough, University of Maine Cooperative Extension. June 1996. Revised by Charles Armstrong, University of Maine Cooperative Extension. February 2002.
  • Fertilizing A New Cranberry Bog (From Carolyn DeMoranville, Cranberry Plant Nutritionist, Univ. of Massachusetts, Cranberry Experiment Station, East Wareham, MA. 1996.)