The use of proper varieties is very important. Slow-growing, slow-bolting
(slow seed-stalk development as day length increases) varieties are used for
late spring and summer harvest, while fast-growing (these tend to be fast bolting), vigorous
varieties should be used for fall, winter, and early spring harvest. Although long days and
increasing temperature predispose spinach to bolting, bolting is increased by exposure
of young plants to low (40-60 F) temperatures.
Disease resistance in spinach varieties is developed for the season to
which the variety is adapted. With proper varieties, spinach production for the fresh market is
possible almost year-round in western Oregon.
Traditionally, prickly-seeded varieties were known as fall harvest, and
winter types, while round-seeded varieties were referred to as summer spinach.
However, new varieties of round-seeded spinach make these designations less accurate.
Flat, semisavoy, and savoy leaf varieties are used for different markets.
The flat and some of the semisavoy varieties are used for processing. All three types are
used for fresh market with semisavoy and savoy types predominating.
Spinach varieties may also be classified as prostrate, semi-erect, and
upright. When the savoy
types are used for processing, plant growth regulators may sometimes be
applied before harvest to cause a more upright leaf growth and reduce the risk of soil contamination.
This is important due to the difficulty in removing soil from savoy leaves during washing and
SPINACH VARIETIES (approximately 40-50 days).
Where downy mildew (Peronospora effusa) may be a problem,
select resistant varieties such as Baker, Cascade, and Olympia, which have resistance to races 1, 2 and 3 of downy
mildew. Resistant varieties for trial: Polka, Rainier,
Shasta, Wolter. A new race 4 has been identified in California in 1989 to which these and most
commercial varieties are susceptible. Research in California indicates that the varieties Bossanova and
Bolero have resistance to strain 4. The variety Coho has resistance to White
Beet Western Yellows tolerance for trial: Ambassador, Rainier,
Rhythm 9, and Hybrid #7.
Savoy types used where Cucumber Mosaic Virus may be a problem are
Bloomsdale Long Standing and Winter Bloomsdale. These may be planted in fall, winter or early
Exceptional bolting tolerance: Tyee, Olympia, Skookum,
Bejo 1369, Splendor, Coho.
Moderate tolerance to bolting: Bloomsdale Long
Standing, Melody, Indian Summer. For trial: Avon, Correnta, Nordic IV, Savoy Supreme,
Space, Spokane, Springfield, Steadfast, Unipak 12.
Spinach is direct seeded from March through September as weather permits.
Planting dates for certain varieties are chosen so as to grow the most
vigorous variety possible and yet avoid the risk of bolting. Bolting risk increases as daylength,
temperature, and plant density increases and as soil moisture or plant nutrients decrease. Suggested
Planting Dates Leaf Type and Variety
Flat Semi-Savoy Savoy
Early (winter or Baker, Polka, Avon, Baker, Savoy Supreme
before May 1) Symphony, Wolter Melody, Skookum,
Exceptional bolting tolerance: Bejo 1369, Splendor
Asian leaf type for trial: Imperial Sun.
Resistance to Downy Mildew strains 1,2,3 and 4: Bolero,
Bossanova (both flat leaf)
Mid-season (May 1 Baker, Olympia, Melody, Skookum Bloomsdale L.S.
to July 31) Polka, Symphony Tyee, Indian
Exceptional bolting tolerance: Bejo 1369, Splendor
Beet Western Yellows tolerance for trial: Ambassador, Rainier,
Rhythm 9, and Hybrid#7
Late (August 1 to Baker, Olympia, Avon, Chinook II Iron Prince,
mid-September) Polka, Wolter Hyb.#7, No.7R, Vienna
St. Helens, Skookum
Overwinter (mid Baker, Cascade, Chinook II, Iron Prince
to late September) St. Helens, No. 7
Asian leaf types for trial: Imperial Express and Imperial Star
Other types of leaf vegetables:
New Zealand spinach (Tetragonia tetragonioides) is a tender
annual with fleshy stems and leaves, resembling spinach. It has very limited commercial demand, but because of its
adaptability to hot summer temperatures and drought, it is popular among some home gardeners.
Spinach beet and Swiss chard (Beta vulgaris Cicla group), a form
of common table beet or leaf beet, grown for their succulent leaves which can be harvested over an extended
period. Swiss chard has large, well developed petioles that may be red, white or green.
These are grown for limited markets, and primarily in home gardens. Sugar beet leaves may also be
used as a substitute for spinach, and are considered superior to table beet leaves. See
separate file Beets and Chard.
Malabar spinach is in a different family altogether. The genus is
Basella, and three species are common: B. rubra, B. alba, and B. cordifolia, which are red stem,
green stem, and heart-shaped leaf forms,
respectively. This is a warm-season crop which produces aggressive vines that
may reach 10-15
feet in length. The succulent leaves and tender shoots are marketed at
specialty markets and are
used the same as spinach.
Muck soils provide needed organic matter and high, uniform, moisture
content. Sandy loams may be used. A pH of 6.2 to 6.9 is optimum with a pH. between 6.5 and 7.0 being
ideal for good growth. Spinach grows very poorly at pH below 6.0.
SEED AND SEED TREATMENT
Summer spinach variety seed numbers approximately 2,800 per ounce, while
New Zealand spinach seed numbers about 350 per ounce. Use only seed that has been fungicide-treated. Spinach is susceptible to damping off.
Recent research indicates that a temperature of 50-63 F is ideal for optimal growth.
Use a precision seeder to plant about 10 seeds per lineal foot of row.
This will provide about 6-8 plants per foot, the desired stand. Space rows in sets 10-12 inches apart or
singly 18-36 inches apart (about 125,000 to 200,000 plants per acre). This method will require
3-4 lb seed per acre if a precision seeder is used. Without a precision seeder, approximately 10-15
lb of seed (480,000-720,000 seeds) per acre are often used. Generally a lower seeding
rate is used when spinach is planted for processing, and a higher rate when spinach is to be
bunched or bagged. Seeding rates should be reduced when spinach is to be grown during high temperatures.
A soil test is the most accurate guide to fertilizer requirements. As a
general guideline broadcast and disc in the following:
Muck Soils Mineral Soils
Nitrogen (N) 30- 50 lb/acre 60-100 lb/acre
Phosphate (P205) 100-150 lb/acre 100-150 lb/acre
Potash (K20) 0-150 lb/acre 0-150 lb/acre
Micronutrients should be applied only on the basis of soil test.
Spinach is a quick-growing, shallow-rooted crop that is not tolerant of
water stress. Maintain
adequate moisture by frequent irrigation when necessary but avoid irrigation
practices that splash
soil onto the leaves or damage them.
See also the OSU Irrigation Guide for Leafy Greens.
Gibberellic acid (GA) is labelled for use on fall-planted and over-wintered spinach (except in California) to facilitate harvest, to increase yield, and to improve
crop quality. The label calls for a single spray of 6-8 g ai/acre in 10-50 gal/acre, 10-18 days before each anticipated harvest.
Applications should be made when the temperature is at least 40 oF and when dew is present on the leaves. Check the label for other suggestions/restrictions. Bolting may
be promoted if temperatures exceed 75 oF within several days of application. Caution: the use of GA on spinach is suggested for trial only in the Pacific Northwest. We lack
experience with this procedure under our climatic conditions.
HARVESTING, HANDLING, AND STORAGE
The University of California-Davis has a file on Minimal
Processing of Fresh Vegetables that discusses film wrapping and other topics.
Spinach for processing yields are approximately 8 to 10 tons per acre.
Average fresh market yields nationally in 1993
ranged from 160 25-lb bushels per acre in Virginia to 840 bu/acre in California. The national
average yield for six reporting states was 524 bu/acre. Oregon yields are commonly 700-900 22-lb cases/acre.
For processing - harvest before plants are too large or begin to bolt
(usually when 16" to 17" tall).
Sometimes a second cut is made for a chopped pack after suitable regrowth has
At harvest, the first cut is made 6-7 inches above the ground in order
to eliminate as much stem
and petiole as possible for the whole leaf pack. This also is done to avoid
as many of the yellow
or old leaves as possible. At the second cutting, small disks are used to cut
away these yellow or
old leaves and to remove some soil away from the crown to facilitate harvest.
Depending on temperature, and plant density, 3-4 weeks are needed between the first and
second cutting to obtain adequate regrowth.
A number of mechanical harvesters are available for processing spinach. One manufacturer, Pixall (100 Bean St., Clear Lake, WI 54005), makes
harvesters for spinach, beans, peas, peppers, and sweet corn.
For fresh market - plants should be dry and slightly wilted to prevent
petiole breakage. When harvesting
by hand, cut above the crown or soil line and bunch. Care should be taken to
exclude leaves that
are dirty with soil or are yellow. Bunched spinach must be handled extra
carefully to reduce
breakage of plants or bunches during bunching, washing and packaging.
Specialty leaf lettuces and spinach for bag mixes have usually been hand harvested, but
mechanical harvesters for this purpose are now available. Three are:
Freshly cut spinach is highly perishable. Care is needed in keeping
loads from overheating. Loads
must be cooled if they are to be transported long distances to the processing
or packing plant.
Green Crop Harvester, made in England. Sole US distributors are C. and
K. Anderson, Fresh Herb Co., 4114 Oxford Rd, Longmont, CO. The cost $20,000 (1998 prices)
for a 4-foot wide model which hold the greens upright by chain-driven
sweeps and cuts the greens with a reciprocating knife (like a hedge trimmer).
A picture of the machine can be seen in Johnny's Select Seed '98 catalogue,
- Quick Cut harvester, an Italian, battery-powered, walk-behind machine with
a 39", 48" or 54"-wide head and a band-saw cutter. Cost is $11,000. Sold by
Ferrari Tractor CIE, PO Box 1045, Gridley, CA 95948; and
by David Washburn and Meg Anderson of Red Cardinal Farm, 9694 75th St.
North, Stillwater, MN 55082.
- Enha Pro, a human-powered machine designed by Norbert Hufnagl, Field of
Dreams, 117 Fredon Springdale Rd., Newton, NJ 07860.
Cost is $2,429 for a two-head unit and $2,966 for a three-head unit.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Hold spinach at 32 F and 95 to 100% relative humidity. Spinach is very
perishable; hence, it can
be stored for only 10 to 14 days. The temperature should be as close to 32 F
as possible because
spinach deteriorates rapidly at higher temperatures. Crushed ice should be
placed in each package
for rapid cooling and for removing the heat of respiration. Top ice is also
Hydro-cooling and vacuum cooling are other satisfactory cooling methods for
Most spinach for fresh market is prepackaged in perforated plastic bags
to reduce moisture loss
and physical injury. Controlled atmospheres with 10 to 40 percent carbon
dioxide and 10%
oxygen have been found to be beneficial in retarding yellowing and maintaining
Spinach is commonly packaged in 20 to 22-lb cartons packed 2 dozen
each; or 7.5 to 8-lb cartons of 12 film bags, each 10 oz; or 20 to 25-lb
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