Growing Strawberries in Colorado Gardens

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Types and Cultivars

June-bearing cultivars have one large crop in early summer (late June to early July along the Colorado Front Range) with larger fruit and higher yields.  They are less hardy in climates like Colorado with rapid springtime temperature swings, and are often damaged by late spring frosts.  They are popular for freezing and jams with flavorful, aromatic berries.  Suggested cultivars include Honeoye, Guardian, Kent, Redchief, Delite, Jewel, Mesabi, A.C. Wendy, Cabot, Bloominden Gem, Carskill, and Geneva

Ever-bearing cultivars have two crops, one in early summer and a second crop in the fall.  They tend to be more reliable than June bearing cultivar in cold climates like Colorado.  Berries are smaller.  Suggested cultivars include Quinalt, Ogallala, and Fort Laramie

Day-neutral cultivars blossom most of the summer and fall in cycles lasting around six weeks each.  Blossoming will slow or stop during hot weather.  Fruit is typically small.   These are popular for a light, daily harvest through most of the summer and fall.  They need constant, light fertilization and regular removal of runners.  Suggested cultivars include Tribute, Tristar, and Fern.

Strawberry

Figure 1.  Day-neutral cultivars provide a small, continual harvest of fresh strawberries throughout the summer and fall (except in extreme heat).



Plantings and Renewal

The key to a great strawberry patch is well-drained soil high in organic matter.  Strawberries need full sun (eight hours minimum), but do not like reflected heat.  They need protection from wind.  In clayey soils, they work better in raised-beds that provide better drainage.  Strawberries are shallow rooted, and thus intolerant of weed competition.

Due to soil borne diseases, avoid soils where strawberries, raspberries, tomatoes, peppers, eggplant, potatoes, and vine crops (squash, melons, pumpkins and cucumbers) have been growing in the past four years. 

Blossom potential for the following year is based on plant health in the fall.  The strawberry patch may need covering for spring frost protection.

Strawberry plants are fussy about planting depth.  The plant crown (short segment with roots below and leaves above) needs to be at the soil line.  If the plant is too deep (leaf stems buried), the plant rots.  If too shallow (roots exposed), the plant dehydrates.  [Figure 2]

Strawberry planting depth

Figure 2  Strawberries are fussy about planting depth.  The short crown section needs to be at the soil surface.



June-Bearing Strawberry Cultivars

Planting – Since June-bearing cultivar set a lot of runners, they are planted in a matted row system.  Set plants 18-24 inches apart in rows four plus feet apart.  Allow runners from the “mother” plant to fill in a matted row, to a plant population of five to six plants per square foot.  Remove excessive runners.  Prune off runners outside the matted row and all new runners after September 1st.  [Figure 3]

Strawberries in Matted Row
Figure 3.  June-bearing cultivars in matted row system.  Runners from the mother plant fill in a block 18-36 inches wide.



First Season Care – Remove all flowers the first year.  Flowering the first year decreases the growth and next season’s yields.  If growth is weak and leaves are light green, fertilize lightly in June, July, and August.  Use water-soluble fertilizes (like Miracle-Gro, Peters, Rapid Gro, etc.) or one cup of 21-0-0 per 100 square feet (broadcast over bed and water in).

General Care – Fertilize after the summer crop is off with water solubles or one cup 21-0-0 per 100 square feet (broadcast over the patch and water in).  Strawberries need one inch of water (rain plus irrigation) per week during blossoming/fruiting.  Water needs will be significantly less when not in fruit production.  Iron chlorosis (yellow leaves with veins remaining green) is a symptom of over watering.  Renovate every year or restart bed every two to four years

Renovation of June-bearing growing bed

  1. After the fruiting periods, mow or cut foliage to two inches.  Remove all plant debris.
  2. With shallow cultivation, create alternating strips (eight to ten inches wide) of plant left and plants removed.
  3. Allow runners to spread into the cleaned area, up to an optimum plant density of five to six plants per square foot.
  4. Remove excessive runners and all runners after September 1.
  5. In future years, alternate the strips by taking out the plants the plant strips left the previous year.

Everbearing and Day-Neutral Strawberry Cultivars

Planting – Because ever-bearing and day-neutral strawberries have fewer runners, the hill system is typically used.  Set plants 12 inches apart in a double or triple wide row bed.  Remove all runners as they develop.  [Figure 4]

Strawberries in Hill System
Figure 4.  In the Hill System, plants are space 12 inches apart in double or triple rows 12 inches apart.  All runners are removed.



First Season Care – Removed the first flush of flowers, and allow flowers to develop after July 1st.

General Care – Periodically remove all runners.  Fertilizer lightly throughout the growing season using water-soluble or ¼ cups 21-0-0 per 100 square feet (broadcast and water in).  Start a new patch every three to four years.

Harvesting

Pick strawberries every other day during the peak of the season.  If berries are eaten or preserved immediately, harvest only red-ripe fruit and leave the caps on the plants.  If the fruit will not be used for a few days, harvest the berries, caps and all, while still pink.

Winter Care

Keep soil damp until fall frost.  Then, withhold water to help harden off the plants.  A final November watering before soils freeze helps prevent winter-kill from drying.

In cold winter climates, like Colorado, a winter mulch of clean, seed-free straw (or similar material) is recommended.  Apply it when the ground freezes (around December 1st along the Colorado Front Range).  Apply two inches, but not more as it could smother the plants.  In windy areas, bird netting over the mulch helps hold it in place.  Mulching helps protect plants from drying winter winds and from root damage by alternative freezing and thawing of the ground.

In climates with late spring frosts (like Colorado), leave the mulch on as long as possible to restrain plant growth in the early spring.  In March, start checking plants under the mulch for growth.  As growth begins, remove mulch over time, allowing sunlight into the plants.  Some may remain on the soil to keep strawberry fruit off the ground. 

Summer Mulch

Because strawberries are shallow rooted, summer mulch helps stabilize soil moisture and also helps suppress weeds.  Use grass clipping (with no application of weed killers), seed-free straw, or other mulching materials.  On ever-bearing and day-neutral cultivars (where runners are not allowed to set), black plastic mulch may be use.  Plants must spread and cover the plastic mulch before summer heat sets in or it will be too hot.

Common Strawberry Pests

Abiotic

  • Iron chlorosis (yellow leaves with green veins) is a symptom of over-watering.  For additional information, refer to CMG GardenNotes #223, Iron Chlorosis.
  • Winter injury often kills plants.
  • Drought injury (Strawberries are shallow rooted, requiring frequent, light irrigations).
  • Hail readily defoliates strawberries.
  • Wind

Insects and Insect Relatives

  • Lygus bugs feed on fruit. – Control weeds, alfalfa and legumes.  Use insecticidal soap, avoid treating during bloom
  • Aphids
  • Slugs and millipedes – Decrease free moisture with proper watering.  Remove fruit and decaying debris.  Mulch to raise fruit up off the soil.
  • Spider mites bronze leaves.  Populations explode in hot weather and following the use of the insecticide Sevin (carbaryl).
  • Spottedwing drosophila flies can affect ripe strawberries.

Diseases

  • Strawberry leaf spots show as red spots with tan centers on leaves.
  • Powdery mildew shows as white mold on leaves.
  • Botrytis gray mold is the fuzzy mold on fruit.
  • Red stele and black root rot complex are common root disorders.
  • Verticillium wilt is a common soil borne disease.
  • Virus complex – strawberries are prone to a variety of viruses.

Wildlife

  • Birds – Bird netting may be necessary spread above and over the strawberry patch.
  • Rabbits
  • Deer

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Authors: David Whiting and Merrill Kingsbury, Colorado State University Extension. Artwork by David Whiting.

  • CMG GardenNotes are available online at www.cmg.colostate.edu
  • Colorado Master Gardener/Colorado Gardener Certificate Training is made possible by a grant from the Colorado Garden Show, Inc.
  • Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating
  • Extension programs are available to all without discrimination.
  • Colorado Master Gardener LogoNo endorsements of products mentioned is intended nor is criticism implied of products not mentioned.
  • Copyright. 2013. Colorado Master Gardener Program, Colorado State University Extension. All Rights Reserved. CMG GardenNotes may be reproduced without change or additions, for nonprofit educational use.

Revised October 2013

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