NC Cooperative Extension Resources

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Extension Horticultural Specialist
Horticultural Science

Introduction

Spinach is a cool-season crop and belongs to the goose family (Chenopodiaceae) as do beets and Swiss chard. This crop is becoming more popular as evidenced by increases in consumption of both fresh (salads) and processed spinach. It is high in vitamins and minerals. Spinach reaches edible maturity quickly (37 to 45 days) and thrives best during the cool, moist seasons of the year. During periods of warm weather and long days, spinach will produce seed. This cold-hardy crop can withstand hard frosts with accompanying temperatures as low as 20°F. Spinach can be overwintered for early spring production in many areas of the state.

Varieties

  • Melody F1 -- Semi-savoyed type. Plants are large and quick growing with very deep color. This variety is for both spring and fall crops. It is resistant to downy mildew and cucumber mosaic virus.
  • Vienna F1 -- Large savoyed dark green leaves are produced on upright plants. Restrict the variety to fall crops. It has some resistance to downy mildew (race 1, 2, 3).
  • Skookum F1 -- Round semi-savoyed dark green leaves borne on upright plants. Good for spring and fall plantings. Resistant to downy mildew (race 1, 2, 3).
  • Savoy Hybrid 612F -- Deeply savoyed large dark green leaves on an upright plant type. It is good for the fall crop and for shipping fresh and freezing. It can be mechanically harvested. It is resistant to downy mildew and cucumber mosaic virus.
  • Seven R -- Semi-savoyed type. Plants are large and quick growing, good for mechanical harvesting and processing. It has resistance to both race 1 and 2 of downy mildew.
  • Tyee -- Plants are semi-savoy, large, fast growing, very slow bolting, heat and cold tolerant variety.

The savoy varieties are best suited to shipping because they pack looser than the smoother types and therefore "heat" less readily. Savoy varieties are less inclined to wilt or turn yellow. Smooth leaf varieties are easier to clean and prepare for canning and freezing.

Soils

Spinach can be grown successfully on a variety of soils, but a fertile sandy loam high in organic matter is preferred. The use of cover crops and green manure crops is recommended to maintain the soil organic matter. The soil pH should range between 6.4 to 6.8. Note: Spinach is very sensitive to acid soils, thus a soil test prior to planting this crop should be made and, if recommended, the necessary lime applied. Use dolomitic lime if magnesium is required. Low germination, yellowing and browning of the margins and tips of seedling leaves, browning of roots, general slow growth and even death of plants, may indicate that the soil is too acid. If the pH is too high, leaves may have a yellow color referred to as chlorosis.

Fertilizers

Spinach requires a high level of fertility, especially nitrogen. Early spring spinach may require larger quantities of fertilizer than fall crops.

Commercial growers -- per acre requirements on sands and sandy loams are 85 to 120 lb N, 75 to 85 lb P2O5, and 85 to 150 lb K2O. On heavier clay soils, 50 lb/acre of each nutrient should be adequate. Fertilizer is often broadcast and worked into the soil prior to seeding. If the fertilizer is banded at seeding it should be placed along each side of the rows 2 to 3 inches below the level of the seed and 6 inches to the side of the row; fertilizer should never come in contact with the seed. Sidedress with two or more applications of 50 lb/acre of N. Spinach, like beets and a few other crops, requires fairly high boron (B).

Boron deficient spinach has dark roots and numerous small, flattened, yellow leaves and is generally stunted. To prevent the issue, apply 1 lb of boron (10 lb/acre of borax) prior to seeding. Note: Use boron only if needed and only in the amounts mentioned above.

Home gardeners -- apply 3 lb of 10-10-10 per 100 square feet. Fertilizer is often broadcast and worked into the soil prior to seeding. If the fertilizer is banded at seeding it should be placed along each side of the rows 2 to 3 inches below the level of the seed and 6 inches to the side of the row; fertilizer should never come in contact with the seed. Sidedress with two or more applications of 50 lb/acre of N or 0.3 oz of 10-10-10 per 10 feet of row for gardens. Spinach, like beets and a few other crops, requires fairly high boron (B). Boron deficient spinach has dark roots and numerous small, flattened, yellow leaves and is generally stunted. An application of 1 oz Borax per 100 square feet of row, broadcast prior to seeding, should prevent that problem. Note: Use boron only if needed and only in the amounts mentioned above.

Region

Seeding Time

Coastal Plain

February to March
Mid-August to late October

Piedmont

Late February to early April
August to mid-October

Mountains

March to April
Mid-July to mid-September

Spinach seed that is more than a year old, rarely germinates over 80%. Older seed is even less viable and germinates more slowly and irregularly. It is important to use new, fresh seed each year.

Fresh seed germinates readily at 38 to 40°F with good results at 50 to 60°F. Higher soil temperatures result in reduced germination. Multiple rows on a bed will increase production efficiency per unit of land. Beds can range from 3 to 5 ft wide depending on planting and cultivating equipment. Raised beds offer many advantages for spinach production. The spinach may be sown 4 to 6 inches in-row and in rows as close as 10 to 12 inches at a depth of 12- to 34-inch. This spacing will require 10 to 20 lb of seed per acre. The soil should be firmed over the seed to help insure rapid and uniform germination.

Thinning

Precisely seeded spinach is not usually thinned because large individual plants are not needed for a usable product. The in-row spacing can be regulated by adjusting the rate of seeding. In rare cases when thinning is required, it should be to 2 to 4 inches when the plants have two well-formed true leaves.

Pest Management

Weeds* -- Any cultivation used to control weeds on the beds between the rows should be shallow.

Insects* -- Spinach aphid and leafminer are the two predominant insect pests of spinach.

Diseases* -- Downy mildew (bluemold), bacterial soft rot, fusarium wilt, cucumber mosaic virus, Cercospora spot, white rust and Heterosporium spot can all be problems in spinach production.

* For pest management recommendations, check the NCCVR (North Carolina Commercial Vegetable Recommendations, AG-586) or your county Extension center for specific recommendations.

Irrigation

Spinach requires abundant moisture to insure a high quality product. An application of one inch of water every 7 to 10 days when rainfall is inadequate is recommended. Keep soil moist until seedlings have emerged.

Harvesting

Spinach is ready for use as soon as it is edible size and it must be harvested before there is extensive yellowing, breakage and other leaf deterioration or the development of seedstalks. Spinach is usually cut below the crown with a knife, taking care to keep the plants clean and to prevent undue breakage or bruising of the leaves. Spinach should be sorted to remove all yellow or damaged leaves before packing into baskets. If spinach is slightly wilted during packaging or preparation, it will be less subject to breakage. Usually, spinach is washed, repacked, and iced at a central packing shed if it is to be shipped.

Pre-packaging

Spinach is often packed in 1- or 2-lb transparent-film bags; it is one of the chief pre-packaged vegetables. Fresh spinach, harvested with the crowns intact, is known in the trade as "crown-cut" spinach. If this spinach is to be pre-packaged, the crowns are cut off during the packaging operation.

Yields

Good yields of fresh market spinach are from 7,000 to 15,000 lb per acre or 280 to 600 bushel baskets or bushel crates per acre containing 20 to 25 lb each.

Some Conditions that Influence Growth

Spinach quickly bolts (produces a flowerstalk) and produces seed under long day (short night) and warm weather conditions. The terms "long standing" and "slow to bolt" in the seed catalogs are associated with varieties that have shown a slowness in bolting to seed. Best yields are obtained when the days are short and the temperature is moderately cool because the plant will continue to grow without starting to develop a seedstalk. High temperatures are likely to result in leaf yellowing. Soil moisture shortage intensifies the effect of heat.

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Last modified: Dec. 16, 2014, 1:38 p.m.