Strawberry

Strawberry

Site

A good site slopes about 2 feet in 100 feet. This allows good drainage of both water and air. Good air drainage allows the cold air to flow off thus reducing susceptibility to frost injury.

Plants in low areas may be covered by water during winter thaws. Then, when the temperature drops after the thaw, the freezing water may kill the plants. The best growing conditions are full sun and sandy to gravely loam with a pH of 6.0 to 6.5 and a good supply of organic matter. Good drainage is essential for best growth. Strawberry runners root better on light soils. Everbearing varieties may give the best results on rich soil. Avoid sites infested with nutsedge, quackgrass or persistent problem weeds. Spray problem weeds with herbicides before planting the strawberries. If the strawberries follow sod there could be problems with white grubs or wireworms.

Flower Bud Formation

June-bearers form flower buds in the short days of late summer and fall. This is why the strawberry patch should not be neglected after the berries have been picked. Poor care late in the season leads to a poor crop the following year. Low temperatures are needed for the flower buds to complete their development. Everbearers form flower buds in the longest days of summer and flower and fruit in summer and fall. The longer days of summer trigger runner formation.

Varieties

There are many varieties of strawberries. Some suitable for Michigan are listed. Everbearing varieties may not be as productive or have as high a quality as June bearing varieties.

Raritan--Midseason, good flavor and yields but susceptible to stele and wilt diseases. Delite--Late, resistant to stele and wilt but forms too dense a matted row. Redchief--Midseason, resistant to stele and wilt but berries are hard to cap. Holiday--Midseason, large, firm berries but plants are not very disease resistant. Guardian--Midseason, resistant to stele and wilt but berries are light fleshed, rough and green tipped. Earliglow--Early, resistant to stele and wilt. Midway--Midseason, most popular variety in Michigan. Marlate--Late, high quality berries but low yields; berries have light flesh, hard to cap. Gem--Everbearer, hardy and productive but a poor runner producer, berries are soft, acid. Ozark Beauty--Everbearer, best everbearer for Michigan. Scarlet--Midseason, a new variety which shows promise for home gardens.

Planting Strawberries

Strawberries fit into a crop rotation system when grown in the vegetable garden. Strawberries should not follow strawberries, tomatoes, peppers or eggplant. These crops are all susceptible to verticillium wilt. There is no chemical control for this disease. Where wilt has been a problem use only disease resistant varieties. A 100 foot row of strawberries should meet the needs of a family of four.

Have the soil tested before planting. The best yields of strawberries are obtained from new plants set new each year. Everbearers give the best crop the year they are planted. June-bearers give the best crop the year after they are planted.

Purchase virus free plants. Healthy strawberry plants have medium to large crowns and large root systems consisting of light colored roots. Plants with black roots are old and should not be planted.

Plant strawberries as soon as the soil can be worked in the spring. When the plants arrive they should be unpacked and either planted or heeled in. Heeling in is the temporary planting of plants in a trench. Plants should not be left heeled in for longer than 2 to 3 weeks.

Strawberry plant crowns should be at soil level. If set too deep, the crown rots. Do not allow the roots to dry out while the plants are waiting to be planted. Spread the roots out like a fan when planting then firm down the soil around them. The spacing depends on the training system used. Early spring planting promotes the formation of highly productive runner plants.

Training Systems

The most common system is the matted row because it is easy to establish. The plants are set at 2 feet in rows 3 to 4 feet apart. Do not allow the plants to form too many runner plants. An overcrowded matted row produces small berries. The runner plants should be 4 to 6 inches apart with the matted row 15 to 18 inches wide. The finished rows should be about 18 inches apart. This system is used most with June- bearers but it is the least productive training systems for strawberries.

In the hedgerow system plants are set 15 to 18 inches apart in rows spaced 24 to 30 inches apart. Allow only two runners to grow, one from each side of the plant. The runners are trained to grow in line with the row, not out to the sides. In the double hedgerow system each plant is allowed to form 4 runners that are placed diagonally from the row. If you looked down on a double hedgerow system row it would look like a row of X's. The mother plant would be at the center of each X and the runners would form the 4 arms. In either hedgerow system the runner plants end up being about 1 foot apart. This system produces high quality fruit but considerable time is spent getting it established.

To establish the spaced bed system set plants 24 to 36 inches apart in rows that are 42 to 48 inches apart. The runners are placed by hand to give a finished row 15 to 24 inches wide. Space plants 8 inches apart and after the bed is filled, remove all other runners. A great deal of labor is involved in this system. Once established the planting must be gone over to remove surplus runners. The spaced bed system produces larger berries and higher yield than the matted row.

The hill system is used for everbearers. Set the plants 12 to 15 inches apart. Because all runners are removed, 3 rows can grow together to form one large row. The 3 rows are spaced 1 foot apart. Stagger the plants so they do not line up across the row. Space the triple rows 2 feet apart. All of the runners are removed before they are 2 weeks old. This system produces the maximum size berries.

Fertilization

Build up soil organic matter before planting. Well rotted manure is good for strawberries. Use 1/2 bushel per square yard before planting. Ten days after planting fertilize with 12-12-12 at the rate of 2 to 3 pounds per 100 feet of row. Repeat the application again in 4 to 6 weeks. Don't put the fertilizer more than 4 inches away from the crown. Fertilizer can be broadcast over a row if the foliage is dry. Once the fertilizer is applied the foliage is rustled with a broom or rake to get the pellets off the leaves. Applying too much nitrogen causes the plants to make excessive leaf growth and causes soft berries that rot easily. Too much nitrogen will also delay ripening. Bearing beds should not be fertilized in the spring. Wait until after the berries are harvested.

Removing Flower Stalks on New Plants

The flower stalks should be removed from new plantings. Stalks are removed as soon as they appear until the first of July. Allowing the plants to set fruit reduces the amount of runner formation. This reduces the number of plants thus reducing the yield the following year. Varieties that form many runners may only need the flower stalks removed until the plants are established. Blossoms are taken off everbearing varieties for the first 60 to 80 days then the plants can be allowed to set fruit. There is no benefit gained by allowing the fruit to form and then not picking it.

Weed Control

In home plantings the primary weed control methods are shallow cultivation and hoeing. Kill problem perennial weeds with herbicides before planting the strawberries. Mulching will help control weeds. Chemicals may control some weeds in strawberry plantings. These are weak and do not control difficult weed problems.

Mulching

Mulching strawberry plantings is strongly recommended. The mulch provides winter protection, eliminates dirty berries, delays blooming, reduces weed growth, conserves moisture, and decreases fruit rot. Mulch for winter protection is applied in when the temperature is consistently about 20 degrees, normally in November. Plants may be damaged if the mulch is applied too early or too late. If applied to early, a number of warm days may injure the plants. If applied too late, some crown injury may occur due to cold temperatures. Crown injury occurs at temperatures below 20 degrees. The mulch should be put on before the ground freezes.

A 2 to 3 inch layer straw or hay may be used for mulch material. A 1 inch layer of sawdust may be used. Leave the mulch on as long as possible to delay bloom in the spring. Check the plants often then remove the mulch when the leaves begin to grow yellowish green. The plants will grow through a thin layer of mulch. Keep the removed mulch in the planting so it can be used to cover the plants should cold weather occur. Mulches also prevent the plants from being heaved out of the ground.

Watering

Strawberries need generous watering during and immediately following bloom. If the plants get too dry while developing fruit, the fruits will be smaller than they should be. Water during the day and apply 1 to 1 1/2 inches of water per week. This includes any rain that occurs during the week.

Frost Protection

Sprinkling can be used for frost protection. As water freezes on the plants it gives up heat. This heat can prevent plant injury even though they will be covered with ice. Sprinkling provides protection down to 22 degrees. Start the sprinklers as soon as the temperature at plant level reaches 32 degrees. The sprinklers will have to run as long as there is ice on the plants. Once all the ice has melted, the sprinklers may be turned off. Sprinkling offers no protection if used after low temperatures have already caused injury.

Another method of frost protection is covering the plants with the recently removed winter protective mulch.

Harvesting

The first ripe berries appear about 30 days after the first blossoms open. Hot weather hastens ripening, shortens the harvest season and makes frequent picking necessary. In moderate weather harvesting every other day should be sufficient. In hot weather it may be necessary to harvest every day. Pick the berries in the morning when they are cool. Harvest only the ripe berries at a single picking. Berries to be frozen should be left on the plants until fully mature. When harvesting, pick and throw away any diseased, rotted, or injured berries to help control rots. Pinch the stem of the berry between the thumb and forefinger and leave some stem on the berry. If the berry is grabbed and pulled it will be bruised.

Renovating The Bed

A strawberry bed may last only 2 to 3 years. The best year will be the first year after planting but by the third year the yield will be down by about two thirds. A strawberry patch should be renovated only if the plants are vigorous and healthy. The first step, once harvest is done, is to mow off the foliage about 1/2 inch above the crown. The plant crowns are injured if the mower setting is too low. Narrow the rows down to 10 to 12 inches then thin out the plants. Leave only the most vigorous looking plants. For renovation to succeed it must be done right after harvest. After renovation manage the bed just as though it were a new planting. A small amount of mulch can be worked in but excessive amounts should be removed. If the mowing and renovation is delayed too long, yields the next year will be reduced. The yearly application of fertilizer should be put on right after renovation.

Failure to Set Fruit

If the plants bloom but fail to set fruit one reason could be cool, wet weather that prevents the bees from pollinating the flowers. Pollen may be damaged by hot dry weather and may not be able to fertilizer the flower.

Small deformed fruits, or nubbins, may form if the blossoms are injured by frost, cold temperatures, or winds. The tarnished plant bug causes nubbins as will an application of the herbicide 2,4-D applied when the plants are in bloom. The herbicide is used on lawn weeds and may drift onto the strawberries when they are in bloom.

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