Green Man Publishing

Strawberry

Fragaria x ananassas

Introduction: I included the strawberry in fruiting vegetables simply because I didn’t want to create another category for it. It is grown in the same ways as the vegetable crops and really fits into the vegetable garden very well (as well as they fit anywhere). 

Crop value: The strawberry is the small fruit that no garden should be without. It is delicious, easy to grow, produces a lot of fruit in a small area (each plant can produce a quart of berries) and takes little effort to grow. It is also perennial so only needs be planted once (though it is sometimes grown in more intensive ways, or even as an annual).

The enjoyment of fresh strawberries was once limited to early summer, but since the introduction of day neutrals and everbearers, they are now available for a much longer period (often through most of the summer).

Ease of growing: The strawberry is surprisingly easy to grow, especially if you use vigorous newly propagated, virus free plants.

With several types of strawberry available, which one you choose will depend upon the climate and how you want to grow them.

If your growing conditions are suitable, the easiest way to grow them is as a low maintenance, long term perennial.

Nutritional content: Strawberries are rich in sugars, vitamin C, potassium and a variety of beneficial antioxidants (including ellagic acid). They are all the more important because they are eaten in quantity (and are easy to eat in quantity). They contain about 150 calories per pound.      

Climate: Strawberries prefer a mild climate and grow best from 50 – 80°F. Warm days (70 – 80°F) day and cool nights (60 – 65°F) produce the best flavored berries. They don’t like very hot weather and won’t set fruit very readily when it gets much above 80°F.

About Strawberry  

Planning facts
Perennial
Hardiness zones: 3 – 10
Growing temp 65 – 75°F
Plant height: 6 – 9˝
Plant diameter: 8 – 18˝
Plants per person: 5
Plants per sq ft: 1 – 5  

Harvest facts
Harvest period: 6 weeks
Yield per plant: 1 lb
Yield per sq ft: ½ – 2 lb   

The plants need a period of cold weather (between 34 – 55°F) in winter, to allow them to go dormant. Without this rest they won’t produce many flower buds and fruit production will suffer. This can be a problem in milder areas as they are quite hardy and will often continue to grow right through the winter. In such cases they are often treated as annuals and grown from pre-chilled plants.

The plants are quite hardy, but the flowers are easily damaged by late frost. Rain is bad when the plants are fruiting as it can lead to various diseases

Strawberries are grown over a wide geographical area so it is important to choose a variety that is suitable for where you live. Some are day length sensitive and fruit best when there are less than 14 hours of daylight.

Soil 

pH 5.5 (6.0) 7.0

Strawberries can grow in most soils, but prefer a fairly acidic, well-drained, light loam that is rich in organic matter. They don’t like wet soil, so if it is poorly drained you should grow them on a raised bed. They don’t like dry soil either, so make sure the soil has lots of organic matter to retain moisture.

Soil preparation: Before planting you should dig the soil thoroughly, to loosen it and remove perennial weeds.

Add 3 – 4˝ of compost or aged manure to the top 10˝ of soil before planting, along with some fertilizer mix. As it is a perennial you won’t be able to incorporate anything else into the soil for a while.

Be careful not to over-fertilize with nitrogen, as it can result in excessive leaf growth at the expense of flowering and fruiting. It may also make plants more vulnerable to winter frost injury.

For spring planting it is good to grow a green manure/cover crop over the winter and incorporate it into the soil a couple of weeks before planting. Of course you will have to do this quite early in spring, so you can get the plants in the ground and growing.

Strawberry life cycle

Strawberries differ from most of the plants in this book in that they are perennial and propagate themselves vegetatively. A mature plant sends out a stolon (runner) about 6˝ long and then produces a vigorous new plant. Another stolon may arise from this plant and then another stolon, to produce a whole series of plants. A single mother plant can produce up to 10 plantlets in this way.

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A plant start out as a runner in its first year, produces an abundance of berries in its second and third years and then starts to decline. Each individual plant can live for up to 5 or 6 years, but they are usually removed after 3 years, to make way for new plants.

In late summer and fall the plant makes buds that will produce the following years flowers. These go dormant in winter and flower the following spring.

Planning

Strawberries can be grown in a variety of ways. They have been grown as annuals, for two years (they reach peak bearing in this year), three years, five years or as a permanent bed.

Where: Full sun (6 hours or more). It’s a good idea to give your plants their own permanent bed out at the edge of the garden where they can grow undisturbed for several years. A strawberry bed isn’t particularly attractive, but can work as a groundcover.

Avoid planting strawberries in wet areas and frost pockets, especially for early spring crops. Beds recently converted from grassland are not good as they may contain pests that like to feed upon strawberry roots. There should be good air circulation to reduce disease problems.

Ideally you shouldn’t plant strawberries where any Solanum crops (eggplant, peppers potatoes and tomatoes) have grown within three years, as they are all

vulnerable to verticillium wilt.

You can plant strawberries in semi-shade, such as around fruit trees. They won’t be as productive as plants in full sun, but if they are filling otherwise unused space then they are a bonus anyway. You could use some of the surplus runners in this way.

When:

When you plant depends upon your climate and the type of strawberry you are growing.

Spring: Day neutral and everbearing strawberries can produce a large crop in their first year, so they should be planted as soon as the soil is dry enough in spring (you want the maximum early growth, so they will fruit later). With Junebearers early planting isn’t so critical as they have a whole year to get going.

Fall: In mild winter areas strawberries are often planted in fall and may continue to grow slowly right through the winter. Very hard frosts can damage young plants, so cover with mulch if this threatens.

Transplants: Strawberries are most often grown from commercially available transplants. These should be certified disease-free because strawberries are susceptible to virus diseases.

You can often get plants for free from gardening friends, but this brings with it the risk of disease. You have to weigh up whether this risk outweighs the expense of buying plants (it often does, but a lot depends upon where you live) Inspect your free plants carefully, you want large, vigorous, productive plants with plump, light colored roots and dark green leaves (and of course no sign of disease).


Before planting: Newly purchased bundles of plants can be kept in the fridge for a week or so, just be sure to keep them moist. Wrap them in a moist (not wet) paper towel and store in a plastic bag. It’s not a bad idea to soak the roots in water for a while before planting.

Planting

This is best done on a cloudy day, or at least late in the afternoon. Take your time with planting and do it right, your plants will appreciate it. 

The best way to plant is to make a hole large enough to accommodate the fully spread roots (the size of this will vary from plant to plant). Many people make a cone shaped mound of soil at the bottom of the planting hole and spread the roots out evenly over this. Don’t fold the roots over to make them fit, or plant with the roots all matted together.

It is important to put the plant in the ground at the right depth, with all of the roots covered and the fleshy crown on the surface of the soil. If the crown

is too high the plant may dry out. If it’s too low it may rot.

Water thoroughly after planting.

Spacing

A typical row spacing is 15 -24˝ apart in the row, with 36- 48˝ between the rows. However the exact spacing depends on what kind of berries you are growing and how you are growing them.

Spacing June bearers

June bearers produce lots of runners and are often grown in “matted rows” whereby the plants are spaced 18 – 24˝ apart with 48˝ between the rows. They are allowed to produce runners and form a densely matted row (you want about 5 plants for every square foot). After harvest the plants may be cut down (they are often actually mown) to within 2 ½˝ of the ground.

Spacing Everbearers

These are most often grown on a mound system which consists of narrow raised beds about 8˝ high and 24˝ wide. The plants are grown in two offset rows with 12˝ between the plants. Runners are usually removed as they appear to encourage the mother plants to produce more crowns and berries. This system usually produces the largest and highest quality fruit, but requires more work.

A variation on the mound system is the hedgerow system which allows for some runners to create new plants around the mother plants.

Spacing day neutral strawberries

These can fruit abundantly for a long period in summer, but are more temperamental than the other types and don’t produce many runners. They are usually grown on the mound system, in the same way as the everbearers,

Care

Strawberries can be grown fairly casually as a low work crop, but they will be more productive if you look after them.


Watering: For maximum production the plants require a steady supply of moisture, especially in hot weather (which is why good soil is important. Lack of water can seriously reduce yields especially when fruit is growing). It can also impact flower bud formation for the following year.

Give the plants at least 1˝ of water a week during vegetative growth and maybe even more during fruiting (this depends upon the weather of
course). Drip works well and helps to minimize disease.

Water is also very important during late summer, as the flower buds are developing at this time, This will determine the amount of fruit produced next year.

You can damage strawberries by giving them too much water, as wet soil can cause the roots to rot. Don’t just water routinely, you have to be observant and look at local conditions.

Weeding: Strawberries are vulnerable to weeds because they aren’t very tall and don’t cover the ground completely. Keep the bed well weeded and you will get higher yields (this is particularly important when they are getting established). Usually this means hand weeding as hoeing isn’t practical once the plants start to spread.

Removing flowers: When growing June bearers you traditionally pinch out any flower buds that appear during the first year to prevent any fruit being produced. This allows them to devote all of their energy to vegetative growth and results in bigger plants and bigger harvests in future years. However if the plants get big enough you can let them produce some fruit in the first year. With ever-bearing and day neutral varieties you pick off flowers for the first 4 – 6 weeks of flowering to allow the plants to get bigger. After this time you let them flower and produce fruit.

Renewal: Common practice is to allow a plant to produce for two years (its most productive years) and then replace it with a vigorous new runner after its third year.


Runners: Everbearers and day neutrals often have their runners removed during their first year, so they keep on producing the maximum amount of fruit (rather than wasting some of their energy producing new plants). In the second year some runners may be allowed to root (these will replace the mother plants the following year).

You can direct the runners to vacant areas where you want them to root (there is no need to detach them from the mother plant). The first daughter plants are usually the best. Runners that form early in the year on Junebearers will produce berries the following season.

Runners are useful for producing new plants, but you don’t want them to produce so many they get overcrowded. Once the bed has the desired density (5 plants per sq ft) you should pinch out extra runners (or root and remove). These late runners often won’t have time to produce fruit buds anyway.                                                                                     

                         Fertilization: Strawberries are very productive plants and should be fertilized regularly. In particular they should get plenty of phosphorus and potassium as this aids in fruit production.


Top dress with a fertilizer mix annually after fruiting in late summer. This will help the plants produce fruit buds for the following year.

Though fertilization is important you don’t want to over-fertilize, as this can result in excessive leafy growth, which is vulnerable to frost. It also means the plants produce less fruit.


Frost control: Plants should be protected from late frosts as these can damage the flowers and their buds. You can protect them from light frosts with row covers or mulch. Commercial plantings are often protected by overhead sprinklers.

Summer mulch: Mulch is beneficial during the growing season because it suppresses weeds, conserves moisture, keeps the soil cool and keeps berries from contact with the soil. Straw is the commonest mulch though pine needles also work well (and provide desirable acidity).

Plastic mulch (black or green) is now widely used by commercial strawberry growers, as it suppresses weeds and holds in moisture. The plants need to grow and cover the plastic before it gets very warm, otherwise the soil may get too hot.

Winter mulch: In cold winter areas the plants are often covered with several inches of loose mulch (straw or pine needles) to protect the buds over the winter. This is applied after the plants have gone dormant and temperatures start to drop below 20°F. Remove it in early spring so the soil can warm up (not too early though).         

                         Problems

Pests: Slugs, snails, tarnished plant bug, mites, strawberry weevils and spittlebugs can all be a problem.

Birds: In many areas these are one of the biggest problems as they peck the fully ripe fruit. If they become a serious problem you will probably have to net the plants.

Diseases: Strawberries are quite vulnerable to disease when they get overcrowded, are growing in wet soil, or if the fruit and foliage gets wet.


Common diseases include powdery mildew. verticillium and botrytis (fruit rot), leaf spot and red stele.


Viruses: As a long lived perennial, strawberries are prone to virus diseases which can reduce vigor without being obvious. This is why it is best to start with certified disease free plants, rather than using free runners from existing plants.

Various kinds of rot. There are several of these fungus diseases, including gray mold, tan rot, hard rot, leather rot, black seed rot and stem end rot. Help avoid these diseases by using mulch to keep the fruit from contact with the soil. Also provide good air circulation, don’t let the plants remain wet for long periods and don’t allow any fruit to decay on the plant.

Harvesting

When: Strawberries ripen about

4 – 5 weeks after the flowers open.

The most important thing to remember about harvesting strawberries is that they don’t continue to ripen after picking. They must be allowed to ripen fully on the plant, which means they should be fully colored for at least two days. The foolproof way to decide when they are ripe is to eat one – if it tastes great it is ready. If it never tastes great you are growing the wrong variety.

Harvest the fruit every 2 days for best quality and least losses (or even every day during peak season).

You should wait until the berries are dry before harvesting, as wet berries are prone to rot.

How: The fruits bruise easily so be gentle. Pick the whole berry with the calyx and a short ½˝ stem attached, by pinching them with your fingernails. Don’t leave the harvested berries in the sun for any length of time, it is important to keep them cool.

It is also important to remove any diseased, pecked, damaged or over-ripe berries from the plants as you move along the rows harvesting. This will help to minimize problems with pests and disease.

After harvest care
This is a big step towards getting a good harvest the following year.

Fertilize after harvest to supply the plants with necessary nutrients.

June bearing varieties are sometimes mowed to a height of 2 ½ – remove top growth. This is high enough not to damage the crowns.

Thin out the runners so the plants don’t get overcrowded. You can cut out as many as half of the plants and they will soon fill in again.

Keep watering and weeding to maintain general plant health.  

Mulch the plants after they go dormant.  

Storage: The berries can be stored in the fridge for several days in a shallow covered pan (don’t wash them).

For longer term storage they can be frozen (if you have a use for strawberry flavored mush), or made into preserves. They are best used immediately though.


Seed saving: Strawberries are rarely grown from seed, but this is pretty easy to collect. The easiest way is to put the fruit in a blender with water for a few seconds. The heavy seed will settle to the bottom, where it can be collected and cleaned.

You can dig up rooted runners while dormant during the winter and plant them elsewhere. You can also root them directly into a plant pot.

Unusual growing methods

Annual growing: In warmer areas, where they don’t get enough winter chill, strawberries are commonly grown as an annual. These are planted in fall, grow right through the winter, are harvested the following spring and summer and are then replaced.

Growing from seed: Almost all garden strawberries are propagated vegetatively, but there are a few varieties that can be grown from seed. This is pretty easy as the seedlings are quite vigorous. Seed may take 2 – 8 weeks to germinate at 65 – 75°F.

Containers: Strawberries are often grown in containers or even hanging baskets.

Semi-wild growing

If your climate is well suited to growing strawberries you may want to try growing them as wild plants. Simply plant them in suitable spots and let them run wild.

Varieties

Strawberry varieties tend to be quite variable and what does well in one area may not work at all in another. When choosing a variety it is important to find one that will perform well in your garden. They are available in three distinct types.

Junebearers – These are the original strawberries and bear one very large crop over 2 – 4 weeks in early summer. After this they send out an abundance of runners, which grow into new plants. These are the most widely adapted and dependable strawberries and are ideally suited to growing berries for preserves or freezing. There are early, mid-season and late varieties so you can extend the harvest quite a lot by planting several varieties.

Early: Chandler, Earliglow, Annapolis, Delmarvel

Mid-season: Redchief, Honeoye, Guardian, Surecrop

Late: Allstar, Jewel, Sparkle

Day neutrals These bear fruit in several flushes through the summer, which spreads out the harvest considerably. They are fairly temperamental and require favorable conditions (not too hot or too dry), but can work very well. They don’t produce many runners because they concentrate on fruiting instead.

Seascape, Selva, Tribute and Tristar

Everbearers These bear two or three times during the summer and don’t produce many runners, because they concentrate on fruiting instead. They do best in long day areas, where they can produce fruit for months.

Fort Laramie, Ozark Beauty, Quinault

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