Growing Strawberries

Strawberries ripening on the plant.
Barbara H. Smith © 2018 HGIC Clemson Extension

Soil & Site: Strawberries are shallow-rooted and grow best in sandy loam soils that drain well, at a pH between 6.0 and 6.5.

Clay soils drain poorly and are difficult to manage.

In the year prior to planting, destroy all perennial weeds.

Improving Soil Structures and Fertility: Soil structures and fertility may be improved by incorporating organic matter like leaves, chopped straw, compost, rotted, sawdust, or grass clippings in the fall. Digging, rototilling, or plowing these materials into the soil in the fall, the organic material will be well decomposed by planting time in the early spring.

For more information, please refer to HGIC 1655, Soil Conditioning a Establishing a Successful Gardening Foundation.

Soil Testing: Submit a soil sample for nematode assay if there is a history of plant pest nematodes in the planting area. Do not plant strawberries if sting nematodes are present. However, strawberries are resistant to southern root-knot nematode.

A soil analysis for plant nutrients and lime should also be taken several months before planting.

For more information, please refer to HGIC 1652, Soil Testing.

Fertilization: Before planting, amend the soil according to the recommendations of a soil test.

Add any lime amendments three to four months before planting to allow the lime’s neutralization effect to occur. Always apply lime based on the soil analysis results and till the soil to a depth of 6 inches.

If new plants appear light green and do not grow well, side-dress with nitrogen about one month after planting. Apply 3 pounds of calcium nitrate per 100 linear feet of row.

Always apply fertilizer to the plants when the foliage is dry, and gently sweep the plants with a broom immediately following the application. Alternatively, overhead watering can be used to wash the fertilizer from the leaves.

In late winter of the second and subsequent years, broadcast 4 pounds of 10-10-10 fertilizer over the bed per 100 feet of row.

Planting: Two very different production systems are used in South Carolina: the matted row system and the annual hill system.

In the matted row system, plants are set out in the spring of year one, and they produce fruit in the spring of year two.

This system works best in Upstate South Carolina, where strawberry fruit production may continue for several years on the same plants.

The annual hill system is preferred in the Sandhills and Coastal Plain because anthracnose disease usually destroys the matted row plantings before producing fruit.

In this system, plants are set out in the fall (Mid September to Mid October) and fruit the next spring. The planting is usually discarded after the crop is harvested.

Only use anthracnose resistant plants when planting the matted row system in the Sandhills and Coastal Plain. For instance, ’Sweet Charlie’ is resistant, while ‘Chandler’ is very susceptible to anthracnose.

The depth of planting for strawberry is critical. The crown of the plant needs to be slightly above the soil line, with the roots ¼-inch below the soil surface.

Due to the shallow-rooted nature of strawberry plants, it is essential to avoid bending the roots, otherwise known as “J” rooting.

Matted Row System (low input): The matted row system involves planting the mother plants 2 feet apart, the first spring, and letting runners fill the bed during the first summer. Remove the flowers the first year so that no fruit is produced until the second year.

When transplanting in the spring, the temperature should be 40 to 50 ºF; a spring frost generally will not harm new strawberry plants. If the plants arrive early and cannot be planted immediately, store them in a refrigerator.

When soil moisture conditions are ideal for planting, layout two rows that are 4 feet apart, each of the rows should be 2 feet from the edge of the bed. Set the plants 2 feet apart in the rows at the correct depth, so the base of the crown is at the soil level. Press the soil firmly around the roots and water them in.

Water is essential for establishment. Beds should be kept moist throughout this period of development.

Flowers will appear a couple of weeks after the new plants begin to grow. Remove these flowers. This improves establishment and channels food reserves into the production of vigorous runners. During the summer of establishment, allow the strawberry runners to develop to form the matted row.

Strawberries growing using the annual hill system.
Barbara H. Smith © 2018 HGIC Clemson Extension

Annual Hill System (high input): In the central and coastal regions of South Carolina (and during normal winters in western South Carolina), strawberry plants can be set in the fall and harvested the next spring. This reduces the danger of diseases destroying the crop. The varieties Chandler and Camarosa are by far the best for the hill system, but other varieties will produce fair results.

Plants are set 12 inches apart in the row and 12 inches apart between rows on beds that contain two rows.

The beds should be 6 inches high at the shoulder, 8 inches high in the center, and 26 inches wide. An aisle 22 inches wide between beds provides a place to walk.

If the planting is free from anthracnose, it may live for several years and be managed as a matted row system.

Set plants from Sept. 15 to Nov. 15. In the Coastal Plain (usually, October is the best month). Plant earlier in the upstate (usually September is best). Freshly dug plants are planted and watered frequently for the first week after planting. Potted plants can also be used, and these require less watering to establish.

After removing the plants, use a cover crop to protect the soil from erosion, capture any nutrients left over from the crop, and contribute of organic material to the soil.

For more information, please refer to HGIC 1252 Cover Crops.

Watering: Strawberries require moisture during the following “critical” times:

• When plants are set and during dry periods following setting
• Before and during harvest when berry size is developing
• After renovation, as needed, to encourage new runners
• In late August, September, and early October when fruit buds are forming for the next season’s crop.

If rainfall is insufficient during these times, water the plantings weekly to wet the soil to a depth of 6 to 8 inches. Strawberries need 1 to 1½ inches of water per week.

Weeding & Mulching: During the growing season, weeds are best controlled by mulching, hand-pulling, hoeing, and tilling.

In vigorous plantings, cut runners that grow into the aisle.

Periodically check the planting for the development of weeds that need to be removed.

Mulch the beds with a 1- to 2- inch layer of straw (wheat, oat, rye, pine). One bale will cover 100 square feet. Do not use grass clippings to avoid smothering the strawberry plants.

Remove the mulch in the spring when signs of new growth appear. Rake most of the mulch off the tops of the plants. The strawberry plants will grow up through the remaining mulch, which will help keep the berries from getting soiled. A good layer of mulch helps conserve moisture, slows the spread of anthracnose, and keeps the fruit clean.

Renovation or Renewing the Planting: Matted row strawberry plantings may bear fruit for more than one season. Plantings may be kept for two, or possibly three to four, fruiting seasons when properly renovated. The main purpose of renovation is to keep plants from becoming too crowded within the beds. Do not attempt to renew strawberry beds infested with weeds, diseases, or insects; it is better to start over with a new planting.

To renew a planting, follow these steps:

• Take a soil test and apply what the report recommends.
• Mow over the top of the plants to remove the leaves, using a rotary lawnmower with the blade set to 4 inches.
• Avoid damaging the plant’s crowns while mowing.
• Rake the clippings away from plants and dispose of them without damaging the crowns.
• Cut back rows to a 12 to 18-inch wide strip using a cultivator, rototiller, or hoe
• Thin the plants, leaving only the most healthy and vigorous. Plants should be about 6 inches apart in all directions.

Care After Renovation: Keep the beds weed-free and irrigate if rainfall is insufficient. Strawberries need 1 to 1½ inches of water per week.

Apply 3-4 pounds of calcium nitrate per 100 feet of row between mid-August and mid-September. Remember to apply the fertilizer when the foliage is dry, and gently sweep the leaves free of fertilizer. Water can also be used to wash the fertilizer off of the leaves. By late September, the matted rows should have grown to be 2 feet wide. Remove any runners growing into the aisles in late summer.

Freshly picked, ripe, strawberries.
Barbara H. Smith © 2018 HGIC Clemson Extension

Harvest

Strawberry harvest begins in the latter part of March in the Midlands and Coastal plains, early April in the Piedmont, and late April in the mountains. Strawberries should be picked every other day or three times a week. The best time to harvest is early in the morning when berries are still cool. Not all berries ripen at the same time; pick only those that are totally red.

Bird Control

The most effective method to reduce berry loss to birds is to cover the planting with bird netting. Anchor the net around the entire planting; otherwise, birds will walk under it. Place 6- to 8-inch stakes every 2 feet around the planting to anchor the net. Angle the stakes away from the rows so that the net can be hooked over the stakes. Angling the stakes keeps the edge of the net close to the ground, thus preventing birds from getting under it. It only takes a few minutes to remove the net for picking and replace it immediately after.

In addition to covering, there are also some chemical repellents. Cornell University has demonstrated significant reductions in bird feeding activity through the application of sucrose (table sugar) solution. Birds lack the enzymes to digest sucrose, and it is also distasteful to birds. Mix 5 pounds of table sugar in 2 quarts of water and apply it to the plants as the berries begin to color.

Another option could be grape-flavored Kool-Aid. Grapes contain the chemical methyl anthranilate, which discourages birds from feeding. Mix 4 packets of Grape Kool-Aid in 1 gallon of water and apply it to the plants as the berries begin to change color. Methyl anthranilate is supplied commercially as a product called Re-Jex-It.

Other chemical bird repellents are also readily available.

Note: Repellents will require re-application after rainfall and may form part of the solution, but in areas with heavy bird pressure, this is unlikely to be sufficient on its own.

Sanitation: Sanitation is crucial to successful strawberry production. Removal of over-ripe fruit, for example, can reduce insect pest pressure as well as disease pressure. Removing infected leaves from plants can also reduce sources of disease inoculum.

Diseases

Most South Carolina home gardeners produce strawberries as a perennial crop. Below are some problems that threaten homeowner plantings

Symptoms of Anthracnose Crown Rot in strawberries.
Justin Ballew © 2018 Clemson Extension

Anthracnose Crown Rot: Anthracnose crown rot is caused by the fungus Colletotrichum gloeosporioides. The symptoms of anthracnose crown rot start as stunting and wilting of the plants during the middle of the day. This can be over-looked as drought stress. Cutting the crowns open lengthwise will reveal white and reddish-brown streaks, creating a marbled effect. Typically, the plants will die in the year after infection occurs. The disease may be introduced with plants obtained from friends or nurseries. Therefore, it is important to purchase certified disease-free plants from a reputable nursery.

Symptoms of anthracnose on the fruit.
Justin Ballew © 2020 Clemson Extension

Anthracnose Fruit and Leaf: Small dark lesions appear on stolons and petioles in the summer and girdle them, killing the leaves and unrooted daughter plants. The fungus spreads from the infected petioles and stolons into the plant’s crown.

The fungus causes round, brown, firm sunken spots on fruit. Once the disease is present, strict sanitation (removal of diseased plant material), mulching, and spraying fungicides every five to seven days can help manage the disease.

Rhizoctonia Root & Crown Rot: The root rot phase of this disease is favored by cool weather, while crown rot worsens during hot weather. Plants typically collapse just as fruiting starts. Bottoms of leaves turn purple and curl up. The original crown is killed, and numerous side crowns may develop. This disease can be prevented by crop rotation with grass crops. The disease may be introduced with plants obtained from friends nurseries. Therefore, it is important to purchase certified disease-free plants from a reputable nursery.

Phytophthora root rot of strawberries.
Justin Ballew © 2018 Clemson Extension

Red Stele Root Rot or Phytophthora Root Rot: The soil-borne water molds Phytophthora fragariae and P. cactorum cause this significant disease. Plants with severe root rot are often stunted, and they may wilt in hot weather. Little or no fruit is produced, and plants eventually may die. The most characteristic root symptom is a reddish discoloration of the stele (core). To minimize the risk of red stele root rot, plant resistant cultivars, or certified disease-free plants and avoid low, wet sites.

Symptoms of Phomopsis leaf blight on strawberry leaves.
Justin Ballew © 2015 Clemson Extension

Phomopsis Leaf Blight: The disease starts to develop in the fall or spring shortly after planting. It spreads rapidly and can kill much of the foliage. It remains active as long as there is green foliage on the plants. If plants become dormant in the winter, the disease will start again in the spring.

Early symptoms are circular, red to purple spots on leaflets. Spots enlarge and develop grey centers. Older spots along veins develop into large V-shaped lesions. Fruit and calyx infection also occurs. The fungus survives in dead leaves attached to the plants.

Leaf Spot & Leaf Scorch: Leaf spot and leaf scorch, caused by the fungi Mycosphaerella fragariae and Diplocarpon earliana, respectively, cause about the same type of damage and are spread in a similar manner. The spores of each fungus are usually brought into a field on new plants or spread to new areas by insects, birds, or farm equipment. Both fungi survive the winter on infected plants.

Leaf spot shows up first on the upper leaf surface as a tiny, round purple spot about one-eighth inch in diameter. At first, the whole spot is purple. Later, the center of the spot becomes gray and then almost white. The border remains purple.

Leaf scorch forms small, dark purple spots on upper leaf surfaces. These spots remain dark purple, never forming a white center like in leaf spot, and have an irregular outline. When numerous, the spots run together, and leaves appear to be scorched.

The loss of foliage due to these two diseases can stunt the entire plant. Severely infected plants may die. During early spring rains, spores from just a few diseased plants can multiply and spread through an entire planting.

Botrytis Fruit Rot: Botrytis fruit rot (gray mold) is the most common and significant fruit disease in South Carolina. While decay can start on any part of the fruit, it usually starts on the calyx end, where moisture may remain in the calyx (or cap leaves) for extended periods. Masses of grey colored spores develop on the fruit as the disease progresses. The funguscan infect all other plant parts. Survival of the fungus occurs in infected tissue and in small, oval, black sclerotia on the ground or plants.

Symptoms of Botrytis(gray mold) on strawberries.
Justin Ballew © 2019 Clemson Extension

These germinate in the spring when flowering starts and infects floral parts. From there, it moves into the fruit and may rot it immediately, or lie dormant until environmental conditions permit development. The disease is most severe in cool, wet weather.

Sanitize plants by removing dead leaves and flowers in late winter. Protecting the flowers and developing fruit with fungicide applications is key to control. However, using strict sanitation, organic growers have successfully produced berries without using fungicides.

Botrytis (gray mold) can also be managed by reducing the periods where leaves and flowers are wet. Overhead irrigation leads to the plants being wet for extended periods, providing ideal growth and development conditions for botrytis and other fungal diseases to develop.

If watering overhead, do so early in the day, so plants are dry by dark. Drip irrigation applies water to the soil and is the preferred method of watering strawberries.

Angular leaf spot symptoms on strawberry leaves.
Justin Ballew © 2015 Clemson Extension

Angular Leaf Spot: This leaf spot bacterium survives in dead plant tissue. The disease starts as small, angular, water-soaked spots on the bottom of the leaves. While areas will expand, the veins limit their size. Spots merge to cover large portions of the leaf and appear as irregular, reddish-brown spots on the leaf’s top. Heavily infected leaves usually die.

Wet weather with daytime temperatures of 70 ºF and night-time temperatures near or below freezing favor disease development. The disease usually stops as temperatures rise in the spring. There is no chemical control for this disease. Regular crop rotation can help reduce bacterial populations.

Sting Nematodes: Sting nematodes are the most common pest nematodes of strawberries in South Carolina. Injured plants appear stunted, may develop nutrient deficiency-type symptoms, and may produce little fruit. No chemical control for sting nematodes is available to homeowners. Proper crop rotation is the best way to prevent the build-up of sting nematodes.

Cultivars & Varieties

For a list of recommended strawberry varieties for South Carolina, refer to HGIC 1404, Strawberry Types.

Table 1: Fungicides for use in strawberries.

Note: Always read, and apply pesticides in accordance with the label.

Originally published 06/99