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GroEdibles Blog

Feb 10

Spotlight Edible of the Day: Strawberries

Posted by GeriMiller on 10 Feb 2012. Filed under  How To Guides, Plant Resources, Spotlight, Warm Season Crops View Comments

“Strawberry fields forever.” The Beatles

Ahhh, strawberries. There’s probably no other fruit that stirs little girl memories like strawberries! Whimsical girlhood memories of Strawberry Shortcake dolls and strawberry scented everything from lipgloss to bubblebath. Oh, and the strawberry milkshakes of a time in my life before milkshakes topped my “DON’T” list.  It’s not surprising then that I am taken back to those memories with every strawberry I plant.

Family – Rosaceae Genus- Fragaria

Did you know that strawberries are in the same family of the rose flower (Rosaceae) and are really not considered a fruit? The part we eat does not consist of the plant’s ovaries (the common definition of fruit), but of the hypanthium (a saucer-shaped structure that holds the ovaries)!
  • Short-day (June-bearing) varieties start forming flower buds as the day length gets shorter and temperatures get cooler. These varieties essentially produce in the late fall, winter and especially in early spring when days are short.
  • Day-neutral (Everbearing) types produce fruit spring through fall. Everbearing or day neutral varieties– produce two crops, one in June or July and other in the fall. Everbearing or day-neutral varieties are insensitive to day length and produce fruit throughout the season as long as night-time temperatures drop below 60° F (Strand, 1993). Day‐neutrals – produce fruit almost continuously through the growing season except when it is very hot. The fruit of everbearers and day‐neutrals typically is smaller, and total seasonal yields often are lower than those of June bearers.
  • NOTE – IF GROWING FOR PRODUCTION – Remove the flower stalks of Short-Day (June-bearing) strawberry plants as they appear throughout the first growing season. More production can be expected if the plants are allowed to attain large size before fruiting. Remove the blossoms of Day-Neutral (Everbearing) types of plants as they appear until about the middle of June (first year only). Then allow flowers to set fruit for harvest during the remainder of the season (August through October).

 

Cultivar recommendations are difficult with strawberries because they tend to be very site specific. Below are some UC Davis recommendations for California:

Short-Day Strawberries

  • Douglas. Early producer; berries very large, good color, good flavor, conical; typically a winter-planted cultivar, planted the first 2 weeks of October.
  • Pajaro. Berries dark red, large, conical, good flavor; principally a summer-planted cultivar used in northern California, planted in August and September.
  • Chandler. Berries exceptional in flavor, color, and size; typically a winter-planted cultivar, but have also been bare-root planted in mid-August.
  • Camarosa. Berries large, excellent flavor; for winter planting.
  • Sequoia. Berries large, soft, excellent flavor; resistant to Verticillium wilt.

 

Day-Neutral Strawberries

  • Selva. Berries exceptionally firm, mild flavor, must be fully red before harvesting; high-yielding; should not be planted before September 10 for optimal performance.
  • Muir. Berries conical, better flavor than Selva and lighter in color.
  • Irvine. Berries conical, medium-sized, excellent flavor; winter-planted.
  • Fern. Berries medium-sized, excellent quality; strongly day-neutral; excellent potential for home gardens because it produces all season long (July-November); plant in the spring as soon as the ground is workable.
  • Hecker. Berries abundant, small to medium-sized, mild flavor, deep red; produces throughout the year; plant in late fall to spring.

Here is a great link to National Sustainable Agriculture Information Service (ATTRA) w/ variety selections for other regions of the US. Please contact your county’s cooperative extension office Master Gardener Hotline to get recommendations for your area.

http://attra.ncat.org/attra-pub/strawberry.html#apxb

Soil Requirements

Choose a well-drained location in full sun. Strawberries are shallow-rooted and grow best in sandy loam soils, which drain well, are well-supplied with humus and have a pH between 6.0 and 6.5. If you haven’t done so recently, take a soil test several months in advance so that you are aware of any deficiencies within enough time before planting to take corrective action. Clay soils drain poorly and are harder to manage but can be improved by adding organic matter. Leaves, chopped straw, compost, rotted sawdust or grass clippings can be used to improve soil structure. Manure applied at 2 to 3 bushels/100 square feet is a good source of organic matter. Apply the organic matter in the fall. Dig it into the soil then so the material will be well decomposed by planting time in early spring. Please use this link to more information regarding how to apply manure safely in your garden:

http://www.gardening.cornell.edu/factsheets/orgmatter/index.html#manures

Clearing weeds well before planting is very important.

Fertilizing

Before planting, broadcast organic fertilizer over the plots. Spade in 3 pounds of 10-10-10 organic fertilizer (contains micronutrients) per 100 square feet of bed.

If new plants appear light green and do not grow well, sidedress with a organic nitrogen fertilizer (blood or bonemeal) about one month after planting. Be careful not to over-apply as excess nitrogen can burn plants (especially true of Blood Meal as this is pure nitrogen).

Phosphorus-deficient plants are usually dark green with reddish-purple leaf tips and margins. At low pH or in sandy soils, magnesium deficiency may occur. Magnesium deficiency can appear as yellow to white striping between veins of leaves. Older leaves become reddish-purple and leaf tips may die.

Commonly used organic sources of nitrogen, phosphorous, and potassium are bloodmeal (~15% N), bonemeal (~4% N and 21% P2O5), and soybean meal (7% N and 2.3% K2O). Many gardeners choose to use poultry litter or commercially available poultry-litter based products. For example, a 3-2-3 or 3-2-2 poultry litter product can be applied before planting. A blended fertilizer or bonemeal mix (10-10-10) can also be used. A liquid fish-emulsion and seaweed product (average analysis of 4-1-1) may then be used for sidedressing.

I stress that just by adding organic matter such as manure or compost to the soil you will increase the level of nutrients, improve soil microbial activity, and increase water-holding and nutrient-holding capacity. Organic matter also improves the physical condition or texture of the soil for cultivation and improves soil structure so the surface of the soil does not crust. Any soil can be/should be improved through the addition of organic matter. As HGEL has often advised, cover crops are also an important, inexpensive way to add organic matter to the soil, and much of plants N needs can be met via cover cropping.

Cultural Practices

Planting:

Strawberry pots, raised beds…both are great ways to plant. Here are two other techniques used in strawberry production:

Matted Row System (low input): Matted row strawberry plantings may bear fruit for more than one season, and may be kept for two or possibly 3 to 4 fruiting seasons if properly renovated*. The matted row system involves planting the mother plants 2 feet apart the first spring then letting runners fill the bed the first summer. The flowers are removed the first year, so no fruit is produced until the second year.

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

To renew a planting follow these four steps:

  • Broadcast 3 to 4 pounds of a complete organic fertilizer (10-10-10) per 100 feet of row.
  • Mow off the leaves, rake away from plants and dispose of them (take your rotary lawn mower and mow over top of bed, setting blade about 4 inches). Avoid damaging the crowns.
  • Cut back rows with a cultivator, rototiller or hoe to a strip 12 to 18 inches wide.
  • Thin the plants leaving only the most healthy and vigorous. Plants should be about 6 inches apart in all directions.

Annual Hill System (high input): Strawberry plants can be set in the fall and harvested the next spring. This reduces the danger of diseases destroying the crop. 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 and 8 inches high in the center and 26 inches wide. An aisle 22 inches wide between beds should be provided as a place to walk.

When soil moisture conditions are ideal for planting, lay off 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 soil level. Press the soil firmly around the roots and water them in.

A couple of weeks after the new plants begin to grow, flowers will appear. Remove these flowers in the spring of the first year. 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.

Irrigation:

Freshly dug plants are planted and watered intensively for the first week after planting due to their shallow root system. Potted plants can also be used and require less watering to establish. Watering: Strawberries require moisture during the following “critical” times:

  • When plants are set and during dry periods following setting;
  • Just before harvest and during harvest when berry size appears to be suffering;
  • After renovation, as needed, to encourage new runner plant;
  • 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, then water the plantings on a weekly basis to wet the soil to a depth of 6 to 8 inches. Drip irrigation is always best.

Weed Control and Mulching: During the growing season, control weeds by mulching and handpulling. Mulching and handpulling are the best means of control in a small planting. During the winter and spring months, periodically check the planting for the development of winter weeds that should be removed. In late winter mulch the bed 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 because they will smother the strawberry plants.

Remove the straw in the spring when there are signs of new growth. Rake most of the needles off the tops of the plants. The strawberry plants will grow up through the needles, which will help keep the berries from getting soiled. A good layer of mulch prevents bitter rot and hard rot and slows anthracnose spread in addition to keeping the berries clean.

Organic Pest/Disease Control

Pest Management

Bird Control

Because there is not much food available for birds when strawberries ripen, birds can be a serious problem. The most effective method to keep them from getting most of the fruit is to cover the planting with bird netting. The net will have to be anchored all the way around the planting, otherwise the birds will walk under it. To anchor the net, place 6- to 8-inch stakes around the planting every 2 feet. Angle the stakes out away from the rows so that the net can be hooked over the stakes. This will keep the edge of the net close to the ground and keep the birds from getting under the net. It takes only a few minutes to remove the net for picking and to replace it after you are through.

Here is a link to UC Davis IPM site about some common pests and diseases of strawberries in California: http://www.ipm.ucdavis.edu/PMG/selectnewpest.strawberry.html

Disease Management

Strawberries are grown in many parts of So. California by home gardeners as a perennial crop. Anthracnose, root-knot nematode, Pythium, Rhizoctonia root and crown rot, Mycosphaerella and Diplocarpon leaf spots, and Botrytis fruit rot can be problems for homeowners.

Rhizoctonia Root & Crown Rot: The root rot phase of this disease is favored by cool weather while the crown rot is worse during hot weather. Plants typically collapse just as fruiting starts. Bottoms of leaves are 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 or an unknown source. Therefore, it is important to purchase disease-free plants from a reputable nursery.

Red Stele Root Rot or Phytophthora Root Rot: The fungi Phytophthora fragariae and P. cactorum cause this major 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, plant resistant cultivars or certified disease-free plants and avoid low, wet sites. You can look at my Plant Disease photo album for pictures of this disease.

Phomopsis Leaf Blight: Phomopsis leaf spot has become increasingly important in Southern regions of the US in recent years. 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 one-six 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. Fruit infection is prevented by controlling foliar infection.

Botrytis Fruit Rot: Botrytis fruit rot is the most common and important fruit disease in many regions of the US. While rot can start on any part of the fruit, it usually starts on the calyx end or the side of fruits touching infected fruits. Affected fruit becomes light brown. The fungus can also invade all other plant parts. Survival of the fungus occurs in infected tissue and in small, oval, black sclerotia on the ground or plants. It germinates in the spring when bloom starts and infects bloom parts. From these it moves into the fruit and may rot it immediately, or be dormant until the fruit ripens. The disease is most severe in wet weather.

The key to control is preventing fall infection of winter leaves, removal of dying leaves in late winter before the addition of mulch and protection of the blooms with an organic fungicide. Several organic growers actually vacuum up dead leaves using shop vacuum cleaners. Using strict sanitation, organic growers have successfully produced berries without using fungicides.

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. Spots enlarge but are limited by the veins. Spots are translucent when viewed with transmitted light but dark green when viewed with reflected light. Spots coalesce to cover large portions of the leaf and appear as irregular reddish brown spots on the top of the leaf. Heavily infected leaves usually die. The disease is favored by wet weather with day temperatures of 70 ºF and night temperatures near or below freezing. The disease usually stops as temperatures rise in the spring. There is no chemical control for this disease. If the bacteria are introduced, use crop rotation. One year is sufficient.

Leaf Spot and 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. A white center is never formed as with leaf spot. The spots 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.

Anthracnose: The fungi causing anthracnose infect stolons, petioles, crowns, fruit and leaves. Small dark lesions appear on stolons and petioles in the summer and girdle them, killing the leaves and unrooted daughter plants. The fungus grows from the infected petioles and stolons into the crown of the plant, causing a reddish-brown firm rot and the plants wilt and die. The fungus causes round, brown, firm sunken spots on fruit. Normally, death of plants occurs the year after infection occurs. Buying disease-free plants is the best control measure. Once the disease is present, strict sanitation (removal of diseased plant material), mulching and spraying fungicides every five to seven days can result in a 50- to 70-percent harvest.

Prevention in Organic Systems

Prevention of disease through good cultural practices is the most effective means for healthy crop production. To help prevent foliar fungal diseases, keep foliage as dry as possible by watering early in the day so foliage dries quickly, or by using drip irrigation. To reduce soil borne diseases, rotate herbs to different parts of the field each year and remove and destroy all plant debris after final harvest.

In an organic system pest and disease management is based on prevention. The goal is to have a healthy, balanced plant and soil system in which pest populations will be stay within tolerable limits. In a conventional system, synthetic pesticides may help a grower save the current crop from an immediate pest problem; however, in many cases, the problem recurs or another develops AND the cumulative effect of using synthetic fertilizers or pesticides is damaging to the environment, humans and animals. The organic approach is based on the theory that major pest problems usually occur when something is out of balance in the system. These are questions organic gardeners should ask themselves when things seem to be going wrong:

-Are the plants undernourished or stressed from growing too quickly?

-Is there a nutrient imbalance?

-Is the soil too wet or too dry?

-Has a good crop rotation been followed?

-Is there a diversity of plants to support beneficial insects?

Studying the problem and trying to determine why it occurred should help prevent similar problems in the future. This will, of course, take time to learn and develop. Unless gardeners refuse to use any pesticides, they may at times choose to apply some organic pesticides to save a specific crop.

A Word about the Integrated Pest Management (IPM) approach

This is system is well-suited for organic production and one, as a Master Gardener, I always recommend. IPM is a system in which insects, diseases, and weeds are closely monitored, and different methods are used to keep pest populations at levels that are not economically damaging with minimal adverse environmental effects. IPM encompasses use of cultural and biological control methods, use of resistant varieties, and a VERY judicious use of pesticides. HGEL recommends that, In the event pesticides must be used, select ORGANIC ones with low toxicity, non-persistent residues, narrow spectrum of control, and low environmental impact.

How to convert an Inorganic Fertilizer Recommendation to an Organic (Univ. of Georgia) http://pubs.caes.uga.edu/caespubs/pubcd/C853/C853.htm

A Resource Guide for Organic Pest and Disease Management (Cornell Univ.)

http://www.nysaes.cornell.edu/pp/resourceguide/index.php

There are four regional IPM centers in the U.S. – North Central, Northeastern, Southern and Western.

Here is a link to a searchable database to find the IPM sites in your region:

http://www.ipmcenters.org/

There is no guarantee that once an organic system is established there will never be a disease, weed, or insect problem. Stressful conditions that a gardener cannot control will occur, such as weeks of endless rains, droughts, periods of extremely high temperatures, hurricanes, plagues of grasshoppers, or hail. Likewise, if an airborne disease invades your area, your plants will probably be infected. However, with careful observation and preparation, an organic system should progressively have fewer pest problems as years go by.

Harvest/Storage

Harvest:

You should pick strawberries every other day or three times a week. Pick the fruit with about one-quarter of the stem attached. The best time to pick is in early morning when berries are still cool. Not all berries ripen at the same time; pick only those which are fully red.

Storage:

Strawberries are extremely perishable, having a max storage life of only 5-7 days at 32 F and 95 % relative humidity.

Strawberries can be washed, drained, covered, and stored in the refrigerator for later use. After rinsing in a colander under running water, I store them in the frig laying flat in a single layer covered with a moistened paper towel. Leave the caps of the berries on until after they are washed to prevent water from soaking into the berry.

Bits and Pieces

via Whiteonricecouple.com Photo by tdphotography.com

My favorite strawberry drink recipes:

http://www.nj.com/insidejersey/index.ssf/2009/07/strawberry_fields.html

Strawberry Mojito – whiteonricecouple.com

Strawberry Agua Fresca

See the GroEdibles Blog: How to Plan and Plant a Cocktail Garden-scroll down to the Vodka Infusion – Strawberry, Lemon, Mint, Cucumber, Lavender, Red Flame Grape recipe.

 

Videos

This video from the New York Botanical garden shows you how to plant herbs in your strawberry pot (she goes over her way to plant strawberries in these pots too) complete with a way to ensure good drainage in these pots.

Peaceful Valley Farm & Garden Supply

And a beautiful video from WhiteonRiceCouple.com TD Photographers:

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