Strawberries are a widely grown fruit crop in Iowa gardens. Answers to several frequently asked strawberry questions are provided below.
Q. I would like to start a new strawberry bed, can I transplant plants from an existing bed or should I purchase plants from a garden center?
A. Purchase plants from a reliable garden center or mail order nursery. Plants from an old planting may be disease infested. Plants purchased from garden centers and mail-order nurseries should be disease-free.
Q. I planted some strawberry plants this spring. Do the blossoms have to be removed this year?
A. During the first growing season, all the blossoms should be removed from June-bearing strawberries. If the flowers are allowed to develop into berries, their development will reduce plant growth, runner production, and the size of next year's crop. Check the strawberry plants once a week and remove the blossoms by pinching or cutting. Flower production on June-bearing strawberries should stop by early July.
With everbearing and day-neutral strawberries, remove all blossoms until early July. Any flowers which bloom after this period may be allowed to develop into fruit. The first berries should ripen in August and continue until frost.
Q. Is spring a good time to fertilize my June-bearing strawberries?
A. Established plantings of June-bearing strawberries should not be fertilized in spring. Spring fertilization stimulates foliar growth, increases disease problems, and produces softer berries. Lush, vegetative growth makes harvesting more difficult. Also, soft fruit are more likely to be attacked by fruit rots. As a result, a spring fertilizer application may actually reduce the fruit yield. Fertilizer should be applied to June-bearing strawberries during the renovation process immediately after the last harvest of the season. Apply approximately 5 pounds of 10-10-10 or a similar analysis fertilizer per 100 feet of row during renovation.
Q. Why do my strawberries have a slightly bitter taste?
A. The flavor of most fruits and vegetables is influenced by weather conditions. In regards to strawberries, warm sunny weather produces the most flavorful fruit. When the weather is extremely hot, the berries may have a slightly bitter taste. Strawberry plants produce smaller quantities of sugars when the weather is cool and cloudy. As a result, berries are not as sweet when the weather is cool and rainy in May and June.
Leather rot, caused by a fungal disease, can be a problem in wet weather. Infected fruit have a leathery texture and bitter taste.
Q. Grasses are taking over my strawberry patch. How can they be controlled?
A. If the strawberry planting is being overrun with perennial grasses, such as quackgrass or bromegrass, control is not practical. Your best option would be to prepare a new site for a strawberry bed this summer or fall and plant a new bed next spring. It may be possible to control annual grasses, such as crabgrass and foxtail, by hand pulling and hoeing. The pre-emergent herbicide Preen (trifluralin) is not labeled for use on strawberries.
Q. How do you renovate June-bearing strawberries?
A. Renovation of June-bearing strawberries should be done immediately after harvest. Start by mowing off the leaves 1 inch above the crowns of the plants with a rotary mower. (Do not mow the strawberry planting after this one-week period because later mowing destroys new leaf growth.) Rake and remove the plant debris to aid in disease control.
After mowing, narrow the strawberry rows to 8-inch-wide strips. When selecting the part of the row to keep, try to save the younger strawberry plants and remove the older plants. If your strawberry bed is a solid mat of plants, create 8-inch-wide plant strips. The plant strips should be spaced 2 1/2 to 3 feet apart.
Fertilization is the next step in renovation. Apply approximately 5 pounds of 10-10-10 or a similar analysis fertilizer per 100 feet of row to encourage plant growth and development.
Q. When should I mulch my strawberry bed?
A. Strawberries should be mulched in the fall to prevent winter injury. Temperatures below +20°F may kill flower buds and damage the roots and crowns of unmulched plants. Repeated freezing and thawing of the soil through the winter months can heave unmulched plants out of the soil and also damage plants.
Allow the strawberry plants to harden or acclimate to the cool fall temperatures before mulching the bed. In northern Iowa, strawberries are normally mulched in late October to early November. Gardeners in central and southern Iowa should mulch their strawberries in early to mid-November and mid- to late November, respectively.
Excellent mulching materials include clean, weed-free straw and chopped cornstalks. (Leaves are not a good mulch for strawberries. Leaves tend to mat together and do not provide adequate protection.) Apply 3 to 5 inches of the material. After settling, the depth of the mulch should be approximately 2 to 4 inches.
Q. When should I remove the mulch from my strawberry planting?
A. To reduce the chances of frost or freeze damage, leave the mulch on as long as possible. Removal of the mulch in March or early April may encourage the plants to bloom before the danger of frost is past. Temperatures of 32°F or lower may severely damage or destroy open flowers. Since the first flowers produce the largest berries, a late spring frost or freeze can drastically reduce yields.
To determine when to remove the mulch, periodically examine the strawberry plants in spring. Remove the mulch from the strawberry planting when approximately 25% of the plants are producing new growth. New growth will be white or yellow in color. (If possible, the winter mulch on strawberries should remain until mid-April in central Iowa.) When removing the mulch, rake the material to the aisles between rows. If there is a threat of a frost later in the season during bloom, lightly rake the mulch over the strawberry plants.