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FRUIT |
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KEY CONCEPTS
- Grapes
- Brambles
- Strawberries
- Currants and gooseberries
- Blueberries
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STRAWBERRIES
Strawberries are perennial plants that can be easily grown in containers and small spaces. This popular fruit is high in vitamin C.
Plants from the nursery will produce a crop 1 year after spring planting. Strawberries produce a maximum crop for 2 to 3 years. Plants grow from a central crown. Every year branch crowns grow from the mother plant. These branch crowns do not form roots, but they do produce foliage and flowers. Branch crowns and runners crowd each other and the mother plant, reducing productivity over a 3-year period.
The primary root of a strawberry plant lives for one year. New roots form higher on the crown, making the plant look like it is growing out of the ground. These roots are more exposed and easily damaged by winter weather.
At the base of each leaf is an axillary bud that can form runners, flowers or another crown. Roots form at the base of new leaves on runners. A runner can be cut and used as a new plant.
Strawberry flower clusters develop in stages. The earliest flowers produce the biggest berries. Each successive set of flowers produces smaller berries. If frost damages the first flowers, secondary and later flower clusters will still produce, although fruit will be smaller.
There are three basic types of strawberries:
- June-bearing;
- ever-bearing;
- day-neutral.
Each type is classified by the development of flowers in response to length of day. As the names imply, each type has a certain fruiting pattern.
June-bearing strawberries bear one crop of fruit each year. There are early, mid-season and late varieties. The berries are large and the crop is heavy, making this an appropriate type if you are interested in canning and making jellies.
Ever-bearers produce when the days exceed 12 hours of sunlight. This results in a moderately heavy crop in early summer, a few berries throughout the summer, and a lighter crop in late summer or fall. The total harvest of ever-bearers is much less than the single crop of June-bearers. These cultivars produce branch crowns, but few runners.
Day-neutral cultivars produce fruit and runners throughout the growing season with three peaks: early-June, mid-July and late August. Temperatures over 75o F stop bud formation. Cooler soil temperatures result in larger berries. Day-neutral berries are normally smaller than other types. Fruit size is small, but flavor is very good.
A list of varieties recommended for Ohio is presented in Fact Sheet 1424, Reference Fruit.5. Cultivars that are disease resistant, especially to red stele, make good choices.
Buy from a reputable nursery that carries named cultivars that are certified disease-free. Order plants early and request delivery between April 15 and May 15 for planting time. Order on Monday, if plants are shipped, to avoid having plants held in warm buildings over the weekend.
Site selection is critical to strawberry production. Locations that are in low-lying frost pockets will probably result in damaged blossoms. Plants begin to grow and blossom very early in the spring. However, very sunny sites that warm up early in spring encourage premature, frost-susceptible growth. A sunny, north-facing slope is ideal.
Good drainage is important for healthy roots. Plants grow most vigorously in spring and fall, when rain and cool temperatures are more likely. Avoid chronic drainage problems by planting in raised beds or installing drainage pipes and incorporating large amounts of organic matter.
Although strawberries will grow in several different types of soil, the ideal soil is loose and fertile. It should contain large amounts of organic matter and have a pH of 5.8 to 6.5. If there are questions about soil fertility or pH, take a soil test the year prior to planting and amend according to test results.
Certain planting sites should be avoided. If a site was previously planted with grass, kill the grass and allow the ground to lie FALLOW one year before planting. This will expose and kill beetle grubs and wire worms that may have been living in grass roots. These grass-attacking pests will also feed on new strawberry plantings. If the gardener does not wish to wait one year, treat soil prior to planting with diazinon according to label directions.
Avoid sites where eggplants, peppers, potatoes and tomatoes were grown. These crops are susceptible to Verticillium wilt which is also a problem on strawberries.
Plant strawberries in Ohio between April 15 and May 15, as soon as the soil can be worked. If bare-rooted plants are purchased, soak them in water for 20 to 30 minutes prior to planting. A cool, cloudy day is ideal for planting. If plants cannot be set in the ground because of weather or soil moisture, they may be stored in the refrigerator. If plants have begun to show signs of growth, they should be heeled in the garden in a protected site.
Plant strawberry plants with half of the crown above the soil line. Dig the planting hole deep enough for the roots to be planted vertically without bending. Water newly set plants and examine crown position. Watering may cover or expose crowns too much.
There are several systems for plant placement. The following diagram shows one method called MATTED ROW SYSTEM.
This method is used most often with June-bearing plants. Plants are spaced 18 to 30 inches apart. All runners are allowed to root in all directions within 12 to 18 inches. Keep rows narrow to allow ease of care between plants. Ever-bearers should be spaced 18 inches apart because they produce fewer runners.
The hill system is a space-efficient method well suited to small gardens. Use the hill system with ever-bearing and day-neutral varieties. This system uses more plants and takes more time to tend, but plants are easier to cultivate and harvest. The following diagram shows the Hill System.
[diagram of Hill System planting]
Space plants 12 inches apart in three rows, also 12 inches apart. Remove all runners. Plants direct all their energy into becoming established and producing berries. This system produces larger and better quality berries than other systems.
To avoid problems from poorly drained soils, consider raised bed plantings. Plants in raised beds produce deeper roots, more crowns per foot of row and earlier fruit. Raised beds also make picking easier. Drawbacks of raised bed systems include susceptibility to cold winter winds, need for more supplemental watering and more control of runners.
Blossom removal is an important cultural practice in growing strawberries. Blossom removal forces the plant to produce vegetative growth, storing up energy for the following season. This process is different for June-bearing, ever-bearing and day-neutral strawberries. Remove flower stalks of June-bearing plants as they appear throughout the first season. June-bearing plants that are allowed to bloom the first year do not form feeder roots as quickly as those that have been disbudded.
Remove flowers of ever-bearers and day-neutrals the first 6 to 8 weeks after planting. During these early weeks the plants go through an establishment period. If flowers are not removed during this time, stored energy can be depleted by fruit production. Do not remove blossoms on ever-bearers and day-neutrals after this initial establishment period.
Determine soil fertility with a soil test. Apply nutrients prior to planting. A week or 2 after planting, apply 5 ounces of 10-10-10 fertilizer per 100 square feet in a band 4 to 6 inches from the plants. After the first year, apply 10 ounces of 10-10-10 fertilizer per 100 square feet after harvest. Reapply in mid-August.
Avoid fertilizer applications before harvest in the second, third and fourth years. Spring applications may produce excessive vegetative growth, increase disease susceptibility, reduce yield, delay ripening and produce poor quality fruit. Keep fertilizer off leaves to prevent foliage burn.
Strawberries need a steady supply of moisture throughout their growing season. Their shallow root systems make plants susceptible to damage during hot, dry weather. Water is important for fruit set and development and flower formation for the following season.
Water frequently, up to once a day, if weather during harvest is hot and dry. This will improve fruit size and firmness. Continue to water June-bearers after harvest.
Supplemental water should be applied at a rate of 1 to 1-1/2 inches per week from mid-June to mid-August if rainfall does not provide this amount. Contrary to the watering recommendations for many other plants, give strawberries frequent light watering. The soil should not be saturated for more than a few days. Apply water early in the day so that plants dry quickly.
Pollination problems can cause poorly formed or very small fruit. Plant spring-blooming flowers and trees nearby to attract bees to the area. Do not use insecticides during bloom period.
Other pollination problems can be caused by temperature. Cool temperatures can slow pollen germination and prevent complete fertilization. To raise cool spring temperatures, plants can be grown under row covers. However, row covers must be removed periodically so insects can pollinate the flowers.
Mechanical cultivation followed by mulching with 3 to 4 inches of weed-free straw between rows will control weeds. Shallow cultivation is important because 90% of the plant's roots are in the top 6 inches of soil.
Mulch also maintains soil moisture. For winter protection, add enough mulch to cover the entire plant to a depth of 2 to 3 inches. Apply the winter mulch after several sharp freezes (usually in December). Pull the mulch back in spring and use it for blossom protection when late frost is predicted.
RENOVATION is an important practice in the culture of June-bearing strawberries planted in a matted-row system. Renovation accomplishes the following:
- eliminates perennial weeds;
- removes any diseased leaves;
- improves exposure to sunlight;
- increases berry size.
Renovate June-bearing varieties immediately after harvest so that plants have adequate time to regrow by September when bud set occurs. Do not renovate after July 15. After this date, simply narrow the row, replace soil around the crowns and irrigate.
After removing old leaves and narrowing the rows, plants require fertilization to produce a flush of new growth. Continue watering at the rate of 1 inch per week. Watering should be continued after harvest because flower buds for the next year are formed during this stage.
Ever-bearing and day-neutral plants in the hill system are not renovated. Instead, they should be replanted with new plants after 3 years.
Many diseases and insect problems of strawberries can be avoided through cultural practices. The first step in disease control is the selection of disease-resistant cultivars and disease-free new plants.
Two common strawberry diseases are red stele and Verticillium wilt. Red stele is a root disease common in Ohio. It is most destructive in heavy clay soils that become saturated with water during cool weather. Plants in low or poorly drained sections of the garden are more susceptible.
Verticillium wilt is a fungus that attacks strawberries, as well as 300 other different host plants. This makes it difficult to avoid. Weeding and preventing wounding of roots help control this fungus. Do not plant strawberries in areas where previous crops were infected with Verticillium wilt.
Strawberries are susceptible to several fruit rots. Gray mold or botrytis fruit rot is a very common disease. It occurs most during prolonged, cloudy and rainy periods before harvest. To reduce fruit rot problems, practice the following cultural precautions:
- Ensure good drainage and air circulation.
- Mulch with straw or other material that prevents fruit from
touching the soil.
- Correctly space plants and time fertilizer applications.
- Harvest fruit frequently and early in the day.
- Remove all diseased berries and destroy.
- Handle berries carefully to avoid bruising.
If the gardener experiences ongoing disease problems in growing strawberries, identify the disease and treat with the appropriate chemical control according to label instructions. Spray schedules are provided in Ohio State University Extension Bulletin 780, "Controlling Diseases and Insects in Home Fruit Plantings."
Slugs can be a persistent pest in the strawberry patch. Mulch creates the ideal environment for slugs. However, the benefits of mulching far outweigh this disadvantage. Slugs can be controlled by baits or traps, and picking berries as soon as they ripen.
Preventive insecticide sprays are not recommended on strawberries. Check the Reference Section for treatment of specific insect pests, Reference Fruit.6.
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