A member of the Rose family, the Fragaria genus has more than 20 species commonly known as strawberries. Modern strawberries, Fragaria x ananassa, are hybrids of Fragaria virginiana, native to North America, and Fragaria chiloensis, native to the Pacific coasts of North and South America. European species were the original large fruited strawberries sold in markets and some are still grown for local consumption.
Strawberries fall into three categories. June-bearing, which produce March into May in hot climates, have the largest berries and produce one crop at one time. The harvest date varies by 14 days according to cultivar, ranging from 'early-bearing' to 'mid-season' to 'late-bearing'. June-bearing tend to produce the largest total crop by weight and are the commercial crop of choice.
Ever-bearing cultivars produce two crops, one in spring and one in fall. Some
cultivars seem to be a cross between ever-bearing and day-neutral and have the
best characteristics of both.
Day-neutral cultivars have the smallest berries and produce steadily throughout the fruiting season, but produce less total fruit than June-bearing.
The best reason to grow your own strawberries is that home grown strawberries taste far better than those in grocery stores. If there were a "Seven Wonders of the Food World" list, home grown strawberries, picked when fully ripe, would be one of them.
Most strawberry roots grow no more than 6" deep and do not exceed 12" deep. Root growth is inhibited in high temperatures.
Only a few strawberry cultivars survive temperatures over 100°F, even with 50% shade all day. Most strawberry cultivars will not set fruit over 80°F although some will flower in higher temperatures and set fruit when nighttime temperatures are below 80°F. In hot climates, strawberries do best when planted in the fall and harvested in the spring.
USDA hardiness zones: 3-10, depending on cultivar. Flowers are damaged by temperatures below 28°F and should be protected by row covers.
Flowers and Fruits
Strawberry flowers are composite flowers having five, white or pale red petals, and with a conical center composed of many, tiny yellow flowers called florets. They are self-fruitful and do not need another plant for pollination. The flowers bloom in spring for all types and also summer and fall for everbearing and day-neutral varieties.
Botanically, the strawberry is not a berry but an enlarged flower stem covered with seeds. What we call fruit is the swollen end of the flower stem with red skin and sweet red and white flesh. The "seeds" on the outside are fruits of the florets and are really achenes: dry one-seeded fruit that do not open to release the seed inside.
Time until Fruit and Harvest
Strawberries will fruit 4-5 months after planting and produce mature fruit 4-6 weeks after flowering. Pick berries when they are fully colored, without any pale areas on the outside. Wait until they are dark red if possible, and leave a bit of stem on the harvested berry. The flavor is best at dark red. Strawberries do not ripen further after picking.
Plant in the Fall
For hot desert climates, plant in late summer or early fall, not mid-winter. The roots will grow in the fall and blooming will begin in March or April for a spring harvest.
Use Well-Draining Containers, Trays or Raised Garden Beds
Containers should be used without saucers so as to drain better without standing water in the bottom. Containers should not receive direct sun on their sides to avoid overheating roots. Hanging baskets can be used providing the soil does not dry out. Raised garden beds provide better moisture control than flat beds. Some dedicated gardeners use greenhouses with automatic misting to control high temperatures.
Use well drained, high organic soil with a pH of 5.6-6.5 (acidic to slightly acidic). Do not use ordinary desert soil as part of the soil mixture. Premium potting soil with moisture retention works well. The soil should be kept moist.
Not required if soil is properly prepared.
Place root crowns at, or very slightly above, soil level. Root crown level is important – too high and the plant will dry out. Too low and root rot will occur.
Do Not Follow Verticillium-susceptible Plants
Avoid planting strawberries in soil where nightshades (tomato, pepper, peppers, eggplant, etc), melons, okra, mint, blackberries, raspberries and other bramble berries, stone fruits, chrysanthemums, and roses or other strawberry plants were growing less than five years earlier. This will prevent sharing common diseases such as Verticillium Wilt which can linger in soils for many years.
Sun and Shade
While daytime temperatures are routinely over 90°F, strawberry plants must be shielded all day with 50% shade cloth and/or lattice. From Nov 22 to Mar 21, strawberries can be unshaded. The rest of the year, afternoon shade is needed.
With drip irrigation, 1 to 1.5 mil plastic can be placed under and around plants to keep berries clean and reduce moisture loss during warm months. If using straw as mulch, take care not to cover leaves. Straw should not be used as frost protection. Row covers will protect plants from freezing temperatures and provide more sunlight during the day.
Daily in the morning. Pale green leaves indicate overwatering. Small, misshapen berries signify underwatering. Twice a day at the same times will be necessary when temperatures are over 95°F.
In the shortest days of the year, from the first of December to mid-January, watering can be reduced to every other day.
Remove All Runners
Strawberry plants spread themselves by stolons called runners, above-ground roots with nodes that grow new roots into the soil at intervals to produce daughter plants (clones). Cut off all runners to keep the plant's energy devoted to developing roots, leaves and fruit, unless you want more strawberry plants.
Remove Weeds by Hand
Remove weeds by hand to avoid cutting shallow roots. Remove dead or dying leaves and stems, as they appear, to avoid fungal diseases.
Home gardeners can grow strawberries in long, narrow containers, then simply replace the soil and sterilize the containers every 2 years.
In raised garden beds, strawberries should be grown for only two years, then replaced with other crops for five years. Rotation is necessary to avoid the build-up of microbial diseases that attack strawberries. Nightshade family crops, like tomatoes or peppers, cannot be used in the rotation because they share some of the same diseases with strawberries.
Strawberries are heavy feeders that deplete the soil of nutrients. In rotation years without strawberries, leguminous cover crops like field pea and clovers can be used to add nitrogen to the soil. In one experiment, mustard cover crops and broccoli crop residue were plowed into the soil, just before replanting strawberries, to reduce the possibility of Verticillium Wilt. This experiment showed a five year rotation could be achieved instead of the normal seven years.
Birds, rodents, slugs and snails can be a problem. An enclosure of 1/2" wire mesh or tulle fabric on top may be necessary.
Plants that help strawberries include legumes such as beans and alfalfa which put nitrogen into the soil, and plants that attract bees such as borage. Caraway is also considered beneficial because it attracts beneficial wasps.
Experiment with Many Cultivars
Trying different cultivars is the best way to see what grows well in your location with your garden setup.
All Foliage, No Flowers
This can be caused by too much nitrogen in the soil. Do not use nitrogen-only or high nitrogen fertilizers. Some cultivars, such as Quinault, will fail to flower if the soil is not to their liking, even when other cultivars, like Loran or Sequoia, flower in abundance. The soil must be properly acidic, have the right balance of nitrogen, potassium and phosphorous, and not be depleted of nutrients.
Many Flowers, No Fruit
Flowers will not set fruit if temperatures are too high. For some temperature-sensitive cultivars, daytime temps over 80°F will stop setting fruit even when nighttime temperatures are much lower. For other cultivars, low nighttime temperatures will keep them setting fruit.
Fruit Ripen Too Small
Insufficient soil nutrients or insufficient water may cause small fruit. Know what the normal size of the berries on your cultivar of plant are supposed to be.
Fruit are Brown and Shrunken
Insufficient water caused by (1) temperatures over 85-90°F and failure to water twice a day, or (2) plants possibly too close together and competing for water.
Fruit are Deformed - Phyllody
With this rare disease, floral parts are converted to leaves. The fruit have leaves growing out of them, green bumps in place of seeds, and/or tips that have turned bumpy brown. The non-infectious variety is caused by excessive chilling of transplants in storage. This will disappear over the season.
The infectious variety is caused by phytoplasmas, bacteria-like organisms that harm plants and are spread by leafhoppers. These plants will continue to produce deformed fruit and should be destroyed.
Use a mite predator, such as Phytoseiulus persimilis, which can be purchased at garden supply companies specializing in organic controls.
Yellow or Red Leaves
Sometimes older leaves on a strawberry plant will die, and they turn yellow and red in the process because they contain red pigment.
Remove dead and dying leaves as soon as possible to prevent fungal problems.
Red Stele root rot can also cause yellow or red leaves. This fungal disease is caused by poorly draining soil or overly wet soil. If your garden bed drains well, yellow and red leaves are usually normal.
Red stems can be a characteristic of some cultivars and are not a problem by themselves.
Verticillium Wilt is a root and crown disease that causes browning along the margins and veins of a leaf. Do not allow soil to dry completely, and do not place plants where this disease might be present. Remove dying leaves as soon as possible.