Spinach (Spinacia oleracea) is a cool-season crop from the goosefoot family (Chenopodiaceae), related to beets and Swiss chard. Its popularity is rising, reflected in increased consumption both fresh (in salads) and processed. Rich in vitamins and minerals, spinach matures quickly, typically in 37 to 45 days, and grows best in cool, moist conditions. When exposed to warm weather and long days, spinach tends to bolt, producing seeds. This hardy crop can withstand hard frosts, with temperatures as low as 20°F, and can even be overwintered in many regions for early spring harvest.
Temperature
Fresh seed germinates readily at 38 to 40°F with good results at 50 to 60°F. Higher soil temperatures result in reduced germination.
Soil
Spinach can thrive in various soils, but a fertile sandy loam rich in organic matter is ideal. It's essential to firm the soil over the seeds to ensure rapid and uniform germination. To maintain soil organic matter, using cover crops and green manure crops is recommended. The optimal soil pH for spinach is between 6.4 and 6.8. Since spinach is highly sensitive to acidic soils, a soil test should be conducted before planting, and lime should be applied as needed. If magnesium is required, dolomitic lime is a good option. Symptoms of too acidic soil include low germination, yellowing, and browning of seedling leaves, slow growth, and root damage. If the soil pH is too high, chlorosis (yellowing) of the leaves may occur.
Planting
Spinach requires consistent moisture to produce high-quality leaves. When rainfall is insufficient, it's recommended to apply one inch of water every 7 to 10 days. The soil should remain moist until the seedlings have emerged. Spinach tends to bolt (produce a flowerstalk) and go to seed in response to long days (short nights) and warm weather. Varieties labeled as "long standing" or "slow to bolt" are those that have demonstrated resistance to bolting. The best yields are obtained in cooler, shorter days, as this helps the plant continue growing without starting to form a seedstalk. High temperatures can cause leaf yellowing, and inadequate moisture worsens the impact of heat stress.
Spacing
1-3” in row and 12-24” between rows
To increase production efficiency, planting multiple rows on a bed is effective. Beds typically range from 3 to 5 feet wide, depending on the equipment used for planting and cultivation. Raised beds provide numerous benefits for spinach production, including better soil drainage and improved root development. Spinach can be sown in rows 4 to 6 inches apart, with rows spaced as close as 10 to 12 inches. The seed should be planted at a depth of 1/2 to 3/4 inch. This spacing will require approximately 10 to 20 pounds of seed per acre.
Harvest
Spinach should be harvested as soon as it reaches an edible size, before extensive yellowing, leaf breakage, or the development of seedstalks occur. Typically, spinach is cut just below the crown using a knife, ensuring the plants remain clean and minimizing damage to the leaves. Before packing into baskets, spinach should be sorted to remove any yellowed or damaged leaves. If spinach is slightly wilted during packaging or preparation, it is less prone to breakage. For shipping, spinach is often washed, repacked, and iced at a central packing shed to maintain freshness.
For more information, please see links below:
- UCANR - Spinach Production
- University of Illinois - Spinach Guide
- Penn State Extension - Growing Spinach
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