Strawberries for Home Gardens
Table of Contents
Growing strawberries can be interesting and rewarding for the home gardener. Strawberries can be grown anywhere in Ontario. They are the first fruit to ripen and, by choosing suitable varieties, ripe berries can be picked throughout the summer until late fall. Berries are delicious when served fresh and can be frozen, canned, or made into jam, jelly or juice. With proper care, enough berries for a family can be obtained from a relatively small area. The plants also have ornamental value. Choose a sunny location.
Growth in our common varieties is affected greatly by temperature and length of the daylight period. In new plants, runner production occurs during the long days and warm temperatures of summer. Then, in the short, cool days of fall, runnering stops and flower buds form within the plant crown. In the spring, when plants start growth, days are too long for any new flowers to form. The flower clusters already within the crown emerge over a 3 week period in late May and early June. Berries start to ripen 4-5 weeks after the first flowers open and continue to ripen for about 3 weeks. Toward the end of the harvest period, when days are long and warm, plants again grow runners that produce new plants.
"Everbearing" and "day-neutral" varieties are less sensitive to temperature and day length than ordinary varieties. They too form flower buds in the fall, which develop into berries the next summer. However, during the summer they also form flowers which produce berries in late summer and fall.
Strawberries can be grown in most garden soils. However, they grow best in well-drained, sandy loam soils which are well supplied with organic matter. Gravelly soils can be improved by adding organic matter, but extra water and fertilizer are needed for good yields. Clay soils drain poorly and are hard to manage, but can be improved by adding organic matter. Planting on ridges also helps if soils drain poorly. Good drainage is very important as strawberry roots do not grow well in wet soil.
Wherever possible, plant strawberries in soil which has not grown strawberries, raspberries, potatoes, tomatoes, peppers or eggplants in the past 4 or 5 years. This precaution will help avoid serious root diseases such as Verticillium wilt and black root rot.
In the year previous to planting, destroy quack grass and other perennial weeds. Do not permit weeds to go to seed.
A good supply of organic matter in the soil is important. Organic matter improves air and water movement, favours growth of helpful soil organisms, provides nutrients, and increases the water-holding capacity of the soil. Manure applied at 8-12 L/m2 (2-3 bu/100 ft2) is a good source of organic matter. Leaves, chopped hay or straw, peat moss, sawdust, grass clippings, etc., can also be used. Apply the organic material in the fall. Dig, rototill or plow it into the soil so the material will be well decomposed by planting time. If material other than manure is used, add ammonium nitrate at 10-15 g/m2 (1) to help decomposition.
In the spring, apply a complete fertilizer, such as 10-20-20, at 50-75 g/m2 (1) Scatter it evenly and work it into the soil several days ahead of planting. Most soils in Ontario do not need a lime application.
Plant in the spring as soon as the ground can be prepared. This allows plants to become established early and start producing runners. Early-formed runner plants produce more berries than plants formed in late summer and fall. Fall planting is not recommended. Commercial plants are generally not available in the fall.
Use healthy plants which have well-developed crowns and many creamy or white roots. Obtain plants from the Ontario Strawberry Plant Propagation Program. These plants have been produced under guidelines designed to control viruses and other serious pests. A list of strawberry plant propagators in Ontario is available from the Agricultural Information Contact Centre at 1-877-424-1300.
Get plants as close to planting time as possible. Plants are usually sold in plastic bags without soil. If plants must be stored for short periods, keep closed packages in the refrigerator until planting time. The roots may look dry, but it is usually best not to water them during storage because water can cause rotting.
Strawberries are usually grown in the "matted-row" system. Set plants about 60 cm (24 in.) apart in rows which are 90-120 cm (3-4 ft.) apart. Allow runners to develop and produce new plants to fill out the rows.
The "hill" system is useful for poor-runnering varieties such as many of the everbearers. Set plants 25 cm (10 in.) apart in the row and keep all runners removed. In this system, yields are usually best if two or three rows are spaced 25 cm (10 in.) apart and then a walking space of 75 cm (30 in.) left between this group of rows and the next.
Use a spade, shovel, or trowel to set the plants. Dig the hole large enough that the roots can be placed straight downward but spread somewhat. The midpoint of the crown should be level with the surface of the soil. If crowns are set too high, both crowns and roots may dry out. If crowns are buried, they smother and rot. Fill the hole with soil and press the soil firmly around the roots.
Be careful that plants do not dry out during planting. The fine roots will dry out in a few minutes on a sunny, windy day if plants are not covered. If roots are dry, plants can be dipped in water just before planting, but do not leave them sitting in water. Do not leave plastic bags of plants in the sun as the temperature gets very hot inside the bags. After planting, water the plants.
Remove all blossoms that appear a few weeks after plants are set. (For treatment of everbearers see following pages.) Plants grow better and produce more runner plants when blossoms are removed.
Hoe around the plants often enough to destroy weeds and to keep the soil loose. This promotes good growth and permits runner plants to root quickly. Hoeing should be shallow around the plants or the roots will be injured. Areas between rows can be cultivated with hand cultivators or rototillers.
Water during dry periods. Wet the soil to a depth of about 15 cm (6 in.) and let it dry out fairly well before watering again.
Sawdust or other mulching materials may be placed around the plants in the row to keep down weeds, conserve moisture and keep the fruit clean. This is particularly useful for hill-system plantings. Make sure the mulch does not cover the tops of the crowns.
Black plastic film or plastic-coated paper can also be used as a mulch, especially in the hill system. Clear plastic is not suitable because weeds grow under it. Put the plastic on before planting. Bury the edges to hold the plastic in place and then make slits just large enough to plant through. To allow any new runner plants to root in the mulched area, slits must be made in the plastic. After a plastic film is in place it is difficult to add fertilizers to the soil. There may also be some difficulty getting water to the roots. It may be necessary to make some holes in the plastic to permit rain or irrigation water to enter the soil. A small soaker hose could also be left under the plastic to permit watering.
Spacing Runner Plants
In matted rows, space runner plants about 15 cm (6 in.) apart in the row. A small amount of soil can be placed just behind a runner plant to hold it in place. If plants are crowded they do not yield well, and produce small berries. Also, when plants are crowded, blossoms may not be pollinated well and diseases are usually more troublesome.
Keep the rows at a convenient width for picking. Fairly narrow plant rows 45-60 cm (18-24 in.) wide are usually easier to manage than wider ones. However, wider beds can be allowed if garden space is limited. After the desired plant stand is obtained, remove extra runners frequently.
After planting, no more fertilizer is generally needed until late summer. However, if the soil is very sandy or if plants are pale and lack vigor, there may be some benefit from an application of ammonium nitrate in late June or early July. Use the same rate as for an August or September application (see below).
In late August or early September, an application of ammonium nitrate at 15 g/m of row (2) is often useful. Spread it over the plants when the leaves are dry and then brush it off. This fertilizer burns leaves if it is not brushed off quickly, or washed off with water.
Low winter temperatures injure roots, crowns and flower buds. Also, freezing and thawing of the soil lifts plants and breaks roots. With winter protection, strawberry plants can be grown in any part of Ontario.
Cover plants with straw (wheat, oat, rye) in the late fall. Use straw which is free of weed and grain seeds. One bale will cover about 9 m2 (100 ft2). Hay generally has too many grass and weed seeds to make a good mulch. Leaves, grass clippings, etc. are not suitable because they can smother the strawberry plants.
When to Apply
Apply the straw after there have been several light frosts but before the temperature goes much below -7oC. Temperatures below -7oC can cause injury. In southern Ontario, straw is usually applied sometime after mid-November. If applied too soon, before plants are dormant, the straw can cause rotting of leaves and crowns.
When to Remove
Remove the straw in the spring as soon as there are signs of new leaf growth under the straw (usually in late April). New growth under the straw is indicated when new leaves become a pale yellow color. Some of the straw (about ¼) can be left on the plants and plants will grow through it. The rest can be placed between the rows to help smother weeds and keep berries clean. It can also be put back on the plants for frost protection during blossoming.
Frosts often occur when strawberries are in bloom and can injure blossoms or developing berries. Considerable protection can be obtained by covering the plants with 5-7.5 cm (2-3 in.) of loose straw, or with old cloth or paper. Plastic sheets give little or no protection. Keeping plants wet will also give protection, since the change of water to ice on the plants releases heat. Use special sprinklers that deliver about 2.5 mm (1/10 in.) of water per hour, and keep sprinkling to a minimum because excess water is harmful. Start sprinkling when some ice is detected on the plants. Keep irrigating as long as ice continues to form. It is only when all water on blossoms is frozen that risk of injury occurs.
Fertilizer applications to bearing plants are not recommended from the time straw is removed to the end of harvest. Fertilizers applied in this period tend to give excessive leaf growth and lead to problems with fruit rot.
Adequate soil moisture is very important from bloom time to the end of harvest. However, excessive watering can be harmful. As a rough guide, strawberries need about 25 mm (1 in.) of water a week when berries are developing. If rainfall is not sufficient to supply this amount, then plants should be watered. Wet the soil to a depth of about 15 cm (6 in.).
A matted row 10 m (33 ft.) long and about 60 cm (2 ft.) wide should yield about 20 kg (44 lb.). Everbearing varieties usually do not produce as large a summer crop as regular varieties, but the combined summer and fall crops should give good yields.
Vigorous plants may be kept for a second, or even a third or fourth fruiting season (see following section).
As soon as picking is completed, apply 10-10-10 fertilizer at 50-75 g/m2. Spread it evenly over the plants and the alleys between the rows. Foliage should be dry. If plants are not mowed, brush the fertilizer off the plants.
If possible, mow off the leaves with a rotary lawn mower (or hedge clippers) with the blade set high enough so that crowns are not injured. In northern areas where berries ripen late and the growing season is short, do not mow.
After mowing, water the plants to carry the fertilizer down to the roots. Following watering, weeds can be pulled easily. Fertilizing, mowing and watering are done to keep plants growing actively.
In both matted-row and hill plantings, remove runners produced during harvest. They can be removed as they appear, or at the end of harvest. Also, remove all runners which form during the rest of the season, unless some are needed to fill gaps. In this way, only the original plants are kept. These plants should be spaced 15-20 cm (6-8 in.) apart. The preceding method is the best one when plants are kept for a second season only. When plantings are kept for several years, let a few new runner plants develop in the alley along one side of the row. Remove a corresponding number of older plants from the other side of the row. In this way, from 1/3 to 1/2 of the bearing row can be replaced by younger plants.
Apply ammonium nitrate in late August or early September as outlined under 'Care of Young Plants'. Also, apply the straw mulch recommended under 'Winter Protection'.
Treatments for renewed plantings are the same as given under 'Care When Berries Are Developing'.
As mentioned under 'Growth Cycle', everbearing varieties have the ability to produce blossoms in the summer for a late-summer and fall crop.
Culture of everbearers is almost the same as that described for regular varieties. In the year everbearers are planted, remove all blossoms until about the middle of July. The blossoms that form later will produce a late-summer and fall crop. In the following year, these varieties bear a crop at the regular time in early summer. They also will bear a crop in the late summer and fall of the second year, but often the plants bloom very profusely then and blossoms and berries are small. To avoid this, keep some of the new runner plants formed in the spring of the second year to produce the fall crop. Do not mow the foliage of everbearers when renewing the planting.
Floating Row Covers
Spun-bonded floating row covers can be placed over the strawberry plants to produce ripe berries one to two weeks earlier than normal. Remove straw mulch from over the plants in early to mid-April and cover rows with the floating row covers. Secure edges carefully with sandbags or bury the edges with soil. The cover should be removed at 5%-10% bloom to allow pollination, but can be pulled back over the berries at night for extra warmth and 1 - 2 degrees of frost protection.
Tunnels constructed of clear plastic film can be put over strawberry plants in the spring to produce ripe berries one to two weeks earlier than normal. Plastic can also be used to extend fruiting of everbearers in the fall. The following materials can be used to construct tunnels for plant rows about 60 cm (24 in.) wide:
Insert wire hoops about 75 cm (30 in.) apart along the row. Push the ends into the ground to the hooks. Stretch the plastic tightly over the hoops and bury it at each end of the row. Over the plastic and behind each hoop, place a piece of twine. Slip the looped ends over the hooks on the hoop. The twine holds the plastic tightly against the hoops.
Tunnels can be installed early in April in Southern Ontario. Remove the straw mulch first. On sunny days, if the temperature goes above 300oC in the tunnel, ventilate by lifting the plastic from the ground, usually along the side away from the wind. The twine will hold the plastic in place. When plants are in bloom, ventilate the tunnels for some time each day to prevent high humidity and to allow insects to enter for pollination. On frosty nights, the plastic film gives little protection to blossoms, so cover the tunnels with cloth or paper, or apply water to form a layer of ice on the plastic. Remove tunnels when weather turns warm, and save materials for use again.
Plants can be set in holes made in the top and sides of a barrel filled with soil. Some garden centers and nurseries sell forms for planting strawberries in a pyramid shape. Forms can also be homemade. Everbearing varieties are normally used. Barrels and pyramids are mainly useful when garden space is limited, or for ornamental value. Plants should get full sunlight for most of the day for best results.
Climbing and Hanging Basket Strawberries
Everbearing varieties are grown for these uses. Mother plants are set in soil, then runners are either tied up to a trellis or allowed to hang from a suspended mother plant. Fruit production with these methods is likely to be disappointing.
First picking about June 15 at Vineland. Berries are bright medium red, large, fairly firm, and have very good flavor. Very good for freezing and other processing uses. Plants are vigorous, runner well, and are very productive. They also are quite resistant to Verticillium wilt and have some resistance to Botrytis fruit rot.
First picking is about June 18 at Vineland. Berries are large, moderately firm and dark red. Plants are vigorous and productive. Performs best in eastern and northern Ontario.
Slightly earlier than Kent, with a fairly long harvest season. Berries are very large, firm, and bright red, but become very dark when over-mature.
First picking is about June 20 at Vineland. Berries are large, light red, with light interiors. They have good flavour but are only fair as frozen pack.
First picking is about June 18 at Vineland. Especially suitable in northern Ontario. The other varieties listed are generally superior to Sparkle for southern Ontario.
First picking about June 22 at Vineland. Berries are a medium red, somewhat seedy in appearance, large, fairly firm, and have excellent flavor. Good for freezing and other processing uses. Plants are vigorous, runner fairly well, and are very productive.
Everbearing and Day-Neutral
These varieties have not been outstanding in Ontario tests. They are generally less productive than regular varieties and performance varies greatly with location and season. Tribute and Tristar have given fairly good results. Plants of everbearers usually produce few runner plants so do best in the hill system.
Table 1. Performance Ratings of Frozen Strawberries Vineland
Ratings are averages for 4 - 12 years from 1973 to 1988 inclusive. Ratings are on a 0 to 9 scale and were made by 5 - 8 persons each year. 0 = very poor; 5 = acceptable; 9 = excellent. Berries were sliced and frozen as a 5 + 1 pack (5 parts berries + 1 part sugar by weight).
Various manufacturers produce pesticides for use on small fruit crops in home gardens. Follow the manufacturer's instructions and do not apply chemicals closer to picking than the number of days shown on the label.
For more information:
Toll Free: 1-877-424-1300