Strawberries

Overview

Strawberries are perennial plants that offer flavorful, vitamin C-packed fruits and are easily grown in containers and smaller garden spaces. The plants are perennials (returning year after year) and typically produce berries one year after planting then for another two to three years. After that, the plants need to be replaced with new, more productive plants.

To further explain the plants' growth habit, new spurs grow from a central crown. Every year, branch crowns arise and grow on the main crown of the mother plant. These branch crowns do not form roots, but they produce foliage and flowers. Branch crowns and runners crowd and compete with each other and the mother plant; thereby, reducing the productivity of the original strawberry plant over a three-year period. The primary root of a strawberry plant lives for only one year. New roots form higher on the crown, making the plant look as if it is growing out of the ground. These exposed roots are more easily damaged by winter weather.

Ongoing Management

Weed Control & Mulching. Mechanical cultivation followed by mulching with three to four inches of weed-free straw between rows will help to suppress weeds. Mulch also helps to retain soil moisture. For winter protection, add enough clean straw mulch to cover the entire plant to a depth of 2"- 3". Apply the winter mulch after several hard freezes (usually in December) have occurred, and the ground is frozen. Pull the mulch off the strawberry plants into the walkways 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. It involves removal of the foliage, narrowing the overall width of the matted rows to 16"-18", reestablishes the picking and walkway aisles, and shapes and invigorates the entire planting. The process of renovation also:

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 12"-14" of healthy foliage. This new growth is needed by the first week of September when flower buds are set for the following spring season. Do not renovate after July 15. After this date, simply narrow the row width, then replace the soil around any exposed crowns and irrigate.

After removing old leaves and narrowing the row widths, encourage plants to produce a flush of new growth by fertilizing and irrigating. Continue to irrigate plants, if there are no rainfall events to provide the equivalent of one inch of water per week. Watering should continue after harvest and through renovation, because the next season's flower buds are being formed.

Ever-bearing and day-neutral plants in the hill system are not renovated. Instead, they should be replanted with new plants after three years.

Insect & Disease Control. 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 devastating strawberry root fungal diseases are red stele and Verticillium wilt. Red stele is a root disease commonly found in Ohio. It is most destructive in heavy clay soils that become saturated and remain wet during cool weather. Strawberry plants in low or poorly drained sections of the garden are more susceptible.

Verticillium wilt is caused by multiple fungal pathogens, Verticillium albo-atrum and Verticillium dahlia. This fungus attacks strawberries, as well as 300 other different host plants. To control it, try to prevent wounding roots when weeding and manage irrigation to avoid repeatedly saturating the soil. Do not plant strawberries in areas where previous crops were infected with the fungus.

Strawberries are susceptible to several fruit rots, with the most prominent fungal disease being Botrytis cinerea. Botrytis fruit rot is also commonly called gray mold and is a very familiar disease of strawberries. Moist, wet conditions and moderate temperatures (60-70 F) favor the development of this disease. The most important time for control  of botrytis is during bloom, since primary infections are almost exclusively through the blossoms. These flower infections then remain dormant until the berries start to ripen.

Infections most often occur 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 the Ohio State University Extension Bulletin 780, Controlling Diseases and Insects in Home Fruit Plantings. Preventive insecticide sprays are not recommended on strawberries.

Lastly, slugs can also be a persistent pest in the strawberry patch. Moisture, reduced light and high amounts of organic matter, like straw or a mulch, create the ideal environment for slugs. However, the benefits of mulching far outweigh this disadvantage. Slugs can be controlled through the use of baits or traps and picking berries as soon as they ripen

Culture

During the first growing season, blossom removal is an important cultural practice to help establish new strawberries. Blossom removal forces the plant to produce vegetative growth and roots, thereby storing up energy for flower and fruit production the following season. This process is different for each type of strawberry. For June-bearing plants, remove all flower stalks as they appear throughout the first growing 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.

For everbearers and day-neutrals, remove flowers the initial six to eight weeks after planting. During these early weeks the plants go through an establishment period. If flowers are not removed during this time, any accumulation of carbohydrates will be depleted by fruit production. After this initial establishment period of six to eight weeks, there is no need to further remove blossoms.

Fertilization

Soil amendments and fertilizer applications should always be based on the results of a soil test. About two weeks after planting, apply five ounces of 10-10-10 fertilizer per 100 sq. ft. in a band 4"- 6" from the plants. Repeat this application rate again in July and then again mid-August. After the first year harvest, renovate the strawberry planting by cutting off the foliage one inch above the crowns and removing the foliage from the planting. Do not damage the crowns while removing the foliage. Apply 10 oz. of 10-10-10 fertilizer per 100 sq. ft. right after renovation and irrigate in with ½"-1" of water. Repeat this procedure using the same rate again in late-July.

Avoid fertilizer applications before harvesting fruit in the second, third and fourth years. Spring applications of fertilizer may produce excessive vegetative growth, increase disease susceptibility, decrease yield, delay ripening and produce poor quality fruit. Remember to keep fertilizer off leaves to prevent foliage burn.

Watering

Strawberries need a steady supply of moisture throughout their growing season. Their shallow root systems make plants susceptible to stress and damage during hot, dry weather. Water is especially critical for the plant phases of fruit set, development, sizing of fruit 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"-1 ½" per week from mid-June through lateAugust, 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 remain saturated for more than a few hours. Apply water early in the day so plants dry quickly.

Pruning / Cutting Back

(to be completed)

Integrated Pest & Pollinator Mgmt Notes

(see above)

Plant Support Requirements

(to be completed)

Getting Started

Matted-row system

Hill system

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 in the newly set plants and examine the crown position after the bed/ground has settled around them. Make sure the crowns are not too low or too high.

The matted-row system is used most often with June-bearing plants. Plants are spaced 18" to 30" apart. All runners are allowed to root in all directions within 12"-18". Keep rows narrow to allow ease of care between plants. Everbearers should be spaced 18 " 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. In the hill system, use two or three rows per hill. Space plants 12" apart in each row, and allow 12" between rows. Leave a walk way, approximately 18"-24" between planting hills. Remove all runners, so plants direct their energy to becoming established and producing berries. This system produces larger and better quality berries than other systems.

Raised beds help avoid root rot problems from heavy, poorly drained soils. Plants in raised beds also 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 frost heaving, a need for more summer supplemental watering and an increase in removing the runners. For an abundant harvest for first-timers, consider a raised bed of June-bearing strawberries. Start with a 6' x 6' raised bed, and fill it with 25 plants.

Container gardening is a great option for growing strawberries in limited space. Choose a large container or hanging basket with holes in the bottom for drainage. Fill the container with a quality potting soil mix. Plant day-neutral or everbearing varieties to enjoy all season long. Remember to water the plants daily since containers dry out easily. At the end of the season, the containers can be overwintered in a garage or the plants can be discarded to be replaced next season.

Edible ground cover - Strawberry plants form a dense mat that can make an edible ground cover with attractive flowers and lingering green foliage. Plant day-neutral or ever-bearing varieties in full sun or under a less-densely canopied tree like a honey locust. Strawberry plants grown as a ground cover will produce some berries but not as abundantly as a raised bed of June-bearing berries.

Selection of Cultivars

When selecting a type of strawberry plant, consider the fruit use, taste, size, hardiness, harvest time and space available. June-bearing varieties produce a high fruit yield in late spring, while everbearing and day-neutral varieties offer intermittent and continuous crops respectively throughout the growing season. In regards to growth habit, June-bearing varieties tend to sprawl in the garden, while everbearing and day-neutral ones are more compact, making them ideal for borders, terraced beds, containers and groundcover plantings. When growing strawberries for the first time, consider trying multiple varieties and labeling them to see what varieties work best. Some June-bearing favorite varieties for Ohio include 'Annapolis,' 'Earliglow,' 'Honeoye' and 'Surecrop.' To extend the season, try adding day-neutral types like 'Albion,' 'Tribute' and 'Tristar' or everbearing ones like 'Ozark Beauty' and 'Quinault.'

Only purchase and plant strawberry crowns that are certified disease-free. Order plants early and request delivery between April 15 and May 15 depending on local planting times. For mail order, place orders on the first day of the week to avoid having plants held in warm buildings over a weekend.

Site Selection & Preparation

Site selection is critical to strawberry production. A sunny, north-facing slope is ideal. In low-lying areas which are likely frost pockets, blooms can be damaged by frost. In very sunny sites, the spaces warm up early in spring and encourage premature, frostsusceptible growth among the strawberry plants.

Good drainage is important for healthy roots. Plants grow most vigorously in spring and fall, when rain and cool temperatures are more prevalent. Avoid planting in areas in which the soils remain saturated by water, resulting in strawberry roots being killed. These root rots, caused by chronic drainage problems, can be avoided by simply raising the planting beds 3"- 4" or by installing drainage pipes or tiles.

Although strawberries will grow in several different types of soil, the ideal soil is loose and fertile. It should contain 2-3% organic matter and have a pH of 5.8 to 6.5. Be sure to take a soil sample and send it to be tested at a qualified soil testing facility. Follow any recommendations made or apply any amendments to the soil, the fall previous to planting the strawberry crowns. Eliminate any guesswork regarding existing soil nutrients or any lack thereof, and determine the trends of the soil pH to move up, down or remain the same. Always take a soil sample and use the soil test as a guide before applying any lime, sulfur or fertilizers. Soil amendments and fertilizer applications should always be based on the results of a soil test.

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.

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, make sure that the roots remain wrapped and covered and have not dried out from the shipping process.

Pollination Needs

Lack of pollination will result in berries that are misshapen, malformed or very small. To help attract and draw pollinating bees into the area near the strawberries, simply plant some spring-blooming flowers and trees. Do not use insecticides during the bloom period. Other pollination problems may be caused by temperature. Cooler temperatures can slow pollen germination and prevent complete fertilization. Cool spring temperatures can be overcome by using row covers, under which strawberry plants can be grown. However, row covers must be removed periodically, so insects can pollinate the flowers.

More Information

Published Articles

Controlling Diseases and Insects in Home Fruit Plantings, by The Ohio State University Extension
Growing Strawberries in the Home Garden, from The Ohio State University Extension

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