March 24, 2017

Day-neutral Strawberry Production in Minnesota

Emily Hoover, Carl Rosen, Jim Luby, and Suzanne Wold-Burkness
Department of Horticulture Science
Department of Soil, Water, and Climate
Department of Entomology

In Minnesota most of the strawberry cultivars grown are June-bearing; however, day-neutral cultivars can also be grown, and in some instances are used as an effort to extend the strawberry season. Day-neutral strawberries differ from traditional June-bearing types in that they flower and fruit continuously when temperatures are moderate because they are insensitive to day length. In northern climates, June-bearing strawberries form flower buds during the short days of fall, and these buds complete their development and bloom the following spring. While cultivars differ in their ideal climate requirements, most day-neutral strawberries will grow well in the temperature range between 45°F and 85°F. Temperatures lower or higher than these limits will cause the plants to stop growing. Since day-neutral strawberries have shallow root systems, and are sensitive to extreme heat, our hot summers in Minnesota may be a limiting factor. However, overhead irrigation can be used to cool the plants during high heat periods.

Cultivar Selection

In general, there are fewer day-neutral cultivars accessible to Minnesota growers as compared to June-bearing cultivars. However, the cultivars available can be grown productively and are outlined in Table1 (.pdf).

Care of Day-Neutral Cultivars

Day-neutral strawberries prefer the same soil and sites as Junebearing cultivars. Plant them in the early spring, at the same time as June-bearing cultivars (see Commercial Strawberry Production in Minnesota publication for more information).

Plant day-neutral cultivars in the same way as Junebearing cultivars, or, if suitable equipment is available, on a 6-to 8-inch raised bed. The raised bed provides higher spring soil temperatures and better drainage, allowing faster establishment and earlier harvest. Day-neutral cultivars can be planted in single rows 3 feet apart with plants 6 to 9 inches apart in the row, or double or triple rows 8 to 12 inches apart with plants 8 to 12 inches apart within the rows (Figure 1). Multiple rows are usually more productive than single rows. Leave 18 to 24 inches between each series of double or triple rows to allow for movement of pickers and equipment. Apply 1 to 2 inches of straw mulch shortly after planting to keep the berries clean, conserve water, and control weeds. Plastic mulches also may be applied either before or after planting. Black plastic will help warm the soil and encourage growth; in warmer areas, white plastic may be more suitable to avoid high soil temperatures in midsummer. For more information on using plastic mulch, see the Washington State University’s resources on Crop Tunnels and Plastic Mulch.

Figure 1. Plant Spacing of Day-Neutral Strawberry Transplants

Table2 (.pdf) provides a timetable for day-neutral plantings. Remove flowers from day-neutral plants for four to six weeks after planting to encourage vegetative growth. When plants have developed five or six expanded leaves, they should be allowed to flower. In general, day-neutral cultivars do not runner as profusely as Junebearing cultivars; therefore, they require a completely different cultural system. Runner removal is not necessary, especially on cultivars such as Fern and Aptos which produce few runners, but may be desirable through the first six or eight weeks of the season to encourage greater productivity.

Nutrient Management

The day-neutral strawberry has a high demand for certain nutrients because it is fruiting throughout the season while also growing vegetatively. Fertilizer suggestions are provided in Tables 3-5. Make certain to base your phosphorus and potassium application on soil test results. Nitrogen should be split into four to six applications at intervals throughout the season. Soil test and foliar analysis can be used to determine whether micronutrient applications are necessary. Please see the “Nutrient Management” section of “Commercial Strawberry Production in Minnesota” for more information.

Table 3. Nitrogen recommendations for day-neutral strawberries1
  Soil Organic Matter (O.M) Level2    
  Low Medium High Organic Soil3 Method/Timing4
  N to apply (lb/A)
First year 80 70 60 25 Split app.
(apply N/A every 3 to 4 weeks after planting)
Subsequent years 80 70 60 25  
1 Leaf analysis should also be used to help determine nitrogen needs
2 Low = less than 3.1% O.M., medium = 3.1-4.5% O.M., high = 4.6-19% O.M.
3 Organic soil = greater than 19% O.M.
4 Suggested methods of application are a general guide and can be modified when appropriate; if nitrogen is applied in the spring, do not apply more than 15-20 lbs/A

 

Table 4. Phosphorous (P) recommendations for Junebearing strawberries1
  Soil Test P Level (ppm)
Bray-P1
Olsen-P
0-10
0-7
11-20
8-15
21-30
16-25
31-40
26-33
41-50
34-41
51+
42+
  P2O5 to apply (lb/A) based on test results2
Establishment Year 150 125 100 75 50 25
Subsequent Years3 100 50 25 0 0 0
1 Application rates listed below test results
2 Apply and incorporate before planting. If needed during bearing years, apply immediately after renovation.
3 Leaf analysis should also be used to help determine potassium and phosphorous needs

 

Table 5. Potassium (K) recommendations for Junebearing strawberries1
  Soil Test K Level (ppm)
  0-40 41-80 81-120 121-160 161-200 201+
  K2O to apply (lb/A based on test results)2
Establishment Year 200 150 100 50 25 0
Subsequent Years3 100 200 150 100 50 0
1 Application rates listed below test results
2 Apply and incorporate before planting. If needed during bearing years, apply immediately after renovation.
3Leaf analysis should also be used to help determine potassium and phosphorous needs

Weed Management

Weed control can be a problem because herbicides, in general, cannot be applied within 60 days prior to fruit harvest. In addition, day-neutral cultivars have been found to be more sensitive to herbicides than Junebearing cultivars. Therefore hand weeding, hoeing, mulching, and cultivation are weed management options. More information on weed control can be found in

Insect and Disease Management

Day-neutral strawberries are affected by many of the same insects and diseases as mentioned in the Commercial Strawberry Production in Minnesota publication. However, because day-neutral strawberries flower during peak numbers of tarnished plant bug, this insect is extremely damaging to day-neutral strawberries. Therefore preventing damage caused by tarnished plant bug is difficult, and control measures should be taken to manage this insect. Please see the Commercial Strawberry Production in Minnesota and Ohio State University Extension’s Midwest Small Fruit Pest Management Handbook (available for purchase) for control options.

Over-wintering Day-Neutral Plantings

Although day-neutral strawberries do not seem to be as productive during the second year, some growers may wish to over-winter a planting. Irrigation, fertilizer application, and pest control during the second year are similar to the first year. Spring frost protection may be necessary. Additional straw mulch may be needed during the middle of the summer as the old mulch decomposes. Additional herbicide applications may be needed during the fall of the first year (just prior to mulching) or during the early spring of the second year.