Spinach

Revised 1/01 -- Author Reviewed 1/01 HIL-17

Douglas C. Sanders
Extension Horticultural Specialist
Department of Horticultural Science
College of Agriculture & Life Sciences
North Carolina State University

 

Spinach is a cool-season crop and belongs to the goosefoot 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 with-stand hard frosts with accompanying temperatures as low as 20 0F. Spinach can be overwintered for early spring production in many areas of the state.

Varieties

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 before reaching the market. 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. 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. Side-dress 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. An application of 1 lb. of boron (10 lb/acre of borax) 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 0F with good results at 50 to 60 0F. 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 1/2 to 3/4 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 all pest management recommendations check the latest issue of 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 seed-stalks. Spinach for market 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 when packed, 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.


Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.

Published by the North Carolina Cooperative Extension Service


Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.