HORTICULTURE

Cranberry Site Requirements

Eric Hanson, Horticulture Department, Michigan State University

Erik Johnson & Dennis Robinson, Michigan Department of Agriculture

Cranberries are native to all of Michigan. However, successful commercial production requires and combination of suitable climate, soils, and water. Suitability of a specific site is primarily dependent on the soil and water characteristics. This guide is meant to provide a starting point for individuals exploring Michigan for potential cranberry.

Climate

The native range of the American cranberry (Nova Scotia west to Minnesota, and as far south as Virginia and Tennessee) represents widely variable climatic conditions. Commercial production occurs from the moderated marine climates of western Oregon and Washington to the harsh continental climate of central and northern Wisconsin. Most aspects of the Michigan climate fall between these extremes. Historical records and current production operations have demonstrated that the climate in nearly all of Michigan is suitable for cranberries. However, regional climate can affect production practices and costs, and should be considered when investigating potential sites.

Winter Temperatures. Cranberry leaves and buds can be killed by winter temperatures below 10F or higher temperatures accompanied by wind. Cranberry beds in Wisconsin, Massachusetts and New Jersey are typically covered during the winter with a protective layer of ice and/or water since damaging temperature/wind conditions are common. These production areas are in the USDA Hardiness Zones 3 (N. Wisconsin) to 7 (New Jersey). Michigan falls between these extremes (Zone 4 in the western U.P to Zone 6 in southwest lower Michigan).

The severity of the winter in different areas of Michigan will affect winter protection strategies. Operations in most areas of northern Michigan should follow Wisconsin winter protection practices (flooding to produce an ice blanket, reflooding to add thickness to the ice, drawing water out from under the ice). Sites in southern Michigan where winters are more moderate than in Wisconsin present some questions about winter protection. Beds in southern Michigan will need to be re-flooded to form new ice following "winter thaws". Snow accumulations in many areas of southern Michigan could impede ice formation. Winter protection techniques similar to those in Massachusetts or New Jersey may be best suited.

Growing Season Length: Frost Protection Needs. The time between the last killing spring frost and the first fall frost defines the growing season. In natural environments, cranberry fruit need about 150 frost free days to mature. The growing season in cranberry production areas ranges from 280 days in Oregon and Washington to 110 days in northern Wisconsin. The range in Michigan is 100 days in the western U.P. to 170 days in southwest lower Michigan. Although all commercial cranberry operations in Michigan require a sprinkler system to irrigation and to protect the flowers and fruit from spring and fall frosts, those in short season areas will require more frequent frost protection and greater management costs.

Precipitation/Evapotranspiration: Irrigation Requirements. Irrigation requirements depend on the amount of warm-season or growing season (April-September) precipitation and evapotranspiration (amount of water lost to the air from leaves and the soil surface). Production areas in Wisconsin receive 20-22 inches rain during the warm-season, whereas totals for Michigan range from 16 to 22 inches. The lowest April to September totals in Michigan occur in the eastern U.P. (16 inches) and the extreme northern portion of the lower peninsula.

The evapo-transpiration from cranberry bogs in Michigan would likely be similar to that of Wisconsin bogs. Air temperatures and relative humidity, which largely control evapo-transpiration, are generally similar in Wisconsin and Michigan. Because precipitation and water losses through evapo-transpiration are similar, the two states should have similar irrigation needs.

Sprinklers are also used to cool cranberry plants during very warm days. High temperatures with dry winds early in the season may desiccate new growth, whereas hot weather later in the season may scald berries. Temperatures as low as 80F can injure plants in the normally cool Pacific Northwest, whereas 85F may cause injury under New Jersey conditions. Plantings in Michigan may require less water for cooling than plantings at similar latitudes in Wisconsin.

Heat Units and Growing Degree Days. Growing season temperatures affect the growth of cranberry plants and fruit differently. Optimum temperatures appear to be 60-80F. Lower temperatures may limit yields by slowing growth and berry development. Higher temperatures in the summer can scald berries, and hot fall weather inhibits color development. Growing degree days (GDD) are a measure of seasonal heat accumulation. Production areas in Wisconsin usually accumulate 2500 (north-central areas) to 3000 (central) GDD base 45F. The upper peninsula of Michigan receives 2300-2500 GDD base 45, and extreme southern Michigan sees up to 3800 GDD. The U.P receives slightly fewer GDDs than the cooler production areas of Wisconsin, and GDDs in southern Michigan and southern Wisconsin are similar.

It is not clear whether the low growing degree day totals in the U.P. might affect cranberries. Plantings in northern WI apparently yield slightly lower on average than plantings in southern areas of the state. Perhaps this is related to differences in growing degree days. We do not expect low GDD totals to be a serious problem, even in cooler parts of the Upper Peninsula. A commercial planting on Whitefish Point, which likely receives less GDDs than any area of Michigan, appears to be successful.

Soils

Cranberries have traditionally been produced on wetland sites.. These soils meet the basic requirements of a cranberry site: organic or sand surface; acidic pH (3.5 to 5.0); shallow, summer water table (6 to 36 inches); less than a 2% slope. Although these traditional sites are ideally suited to cranberries, they are generally classified as wetlands and their development usually requires a wetland permit.

Some non-traditional soils are now used for cranberry production. These sites are readily available in some areas, and often do not require wetland permits. It is important to recognize that although several basic non-traditional sites have been proposed, the basic requirements listed above need to be met in order to successfully produce cranberries. This may require significant additional development costs. Two categories of non-traditional sites are described below:

Somewhat poorly drained and moderately well drained sands with regional watertables. These soils have sandy surfaces with varying amounts of organic matter, pH of 4.0 to 5.5 in the surface, and water tables 1 to 3 feet (somewhat poorly drained) to 2.5 to 6.0 feet (moderately well drained) during the growing season. Examples would be the AuGres and Croswell soils. An advantage of these soils is that they are not typically classified as wetlands. The major disadvantage is their high permeability, which could lead to problems maintaining desired water table levels. Several newer Wisconsin cranberry operations are on these upland soils.

Somewhat poorly drained and moderately well drained sands with perched water tables. These soils have sandy surface horizons above slowly permeable "clayey" lower horizons at 20 to 40 inches. The pH is 4.6 to 6.0 in the surface material, and the water table is perched at 1 to 6 feet (depending on drainage class) during the growing season. Allendale and Manistee soils are examples. The advantage of these soils is that their slowly permeable substrata can prevent the loss of excessive water from the beds. These soils may not be as common in large continuous areas as some other soils.

Some soil types that fit the general requirements for cranberries (acidic, organic or sand, poor to moderate drainage) are summarized below. Mesic Southern soils are below a line running approximately between Ludington and Bay City. Frigid Northern soils are above this line.

Water

Cranberry production requires large amounts of water. Water is needed to protect plants from frosts in the spring and fall. Most growers frost protect by sprinkling water on plants. Irrigation is also needed to meet the water demands of the plants in the summer. Cranberry plants are shallow rooted and desiccate easily. Sprinklers may also be used to cool the plants during hot summer weather. Beds that are wet harvested are flooded in October with 1 foot of water to remove the berries, and a second 1 ft flood may be used to remove trash from the bed. Beds are again flooded with a foot of water in the winter to protect plants from winter weather. Re-flooding may be necessary following warm spells that melt the ice on beds.

Water Quantities. Water requirements vary with location and management practices, and are often expressed in acre-feet. One acre-foot is the water needed to cover an acre to a depth of one foot (about 330,000 gal). Reported annual water use estimates range from 5 to 9 acre-feet. However, if beds and reservoirs are designed to recycle water, actual water use amounts may be lower. Recycling systems require a soil substrata that minimizes deep seepage losses, and topography that allows for water movement from bed to bed, and from beds to reservoirs.

¹Figures modified from: Cranberry Agriculture in Maine Grower Guide. Maine Cranberry Development Comm., 1993, and Massachusetts Cranberry Production. Univ. Mass. Coop. Ext. Serv., 1993.

Winter and harvest flooding requires enormous quantities of water in a short period of time. As a general rule, at least 2 acre-feet of water should be on hand and immediately available for each acre of cranberry bed. Wells and small ditches or streams usually cannot meet required volumes.

Water Quality

Since large qualities of water are applied to cranberry beds, water quality is particularly important. Water that carries high alkalinity or salt levels can adversely affect soil chemistry and plant health. A common concern in many areas of Michigan is water alkalinity and pH. Alkalinity is a measure of how water resists pH changes, and is expressed as the amount of lime equivalent in the water. Use of water with high alkalinity levels can introduce enough lime to increase the pH of cranberry soils above the desired range (4.0 to 5.5). This will necessitate applications of acidifying materials (sulfur, sulfuric acid) to counteract the liming effects, which increases production costs.

Cranberries are also relatively intolerant of water with high salt levels. Test the water source(s) and use the table below to determine the suitability of potential cranberry sites.

Regulatory Considerations

Generally Accepted Agricultural and Management Practices (GAMP's) for cranberry production were developed by the Michigan Department of Agriculture and other agencies in 1996. These GAMP's break potential cranberry sites into three categories, based on their wetland classification and regulator status. The sites are summarized below. Obtain a copy of the Cranberry GAMP's from the MDA (517 246-0236) for more detail.

"A" sites are either upland or prior wetland areas that were drained for agricultural use and are no longer defined as wetlands. These sites are desirable because their development has relatively little impact on wetland resources and does not require a wetland permit (other local, state or federal permits may be needed). "A" sites may be suitable for cranberries if the high water table is restored (e.g. placement of water control structures on drainage outlets) and other criteria are met.

"B" sites are areas that have been drained for agricultural use but still meet the state and federal definitions of a wetland. These sites require permits for construction of cranberry beds and associated facilities. However, permits will be issued unless other resources would be adversely impacted by the proposed conversion.

"C" sites are natural, undisturbed wetlands. Wetland permits are required for construction of cranberry beds in these areas. Permit requirements will be consistent with federal programs regarding construction of cranberry beds in natural, undisturbed wetlands, and will weigh the impacts and benefits of the proposed project.

How water is to be acquired and discharged are prime concerns. Cranberry operations typically use surface water from existing sources (lakes, streams, ditches), or reservoirs. Access to water from lakes or streams may require permits. Construction of reservoirs of sufficient size may also require permits. Discharge of water to drainage ditches, streams or lakes may also require permits, since the temperature and chemistry of receiving waters can be affected.

Cranberry Expert Team

Schedule a visit by the Cranberry Expert Team for an early assessment of a potential site. The team is comprised of MDA NRCS, MDEQ and MSU experts who can provide an initial assessment of the physical (soils, water) and regulatory characteristics of a site. Call (231 362-2659) to request a site visit.

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Last modified: February 23, 2000