CORVALLIS, Ore. – Planting broadleaf spinach is most successful during the cooler temperatures of spring and fall. Spinach seeds germinate better in cool soils between 55 and 65 degrees, says Deborah Kean, Oregon State University vegetable crops researcher.
If you plant spinach in the summer, some varieties will flower or “bolt” prematurely. They stop growing leaves and set seed.
Kean and her colleagues at OSU’s Vegetable Research Farm in Corvallis have grown various spinach varieties and found one that seems to best tolerate summer’s long days and heat without bolting – Correnta.
Traditional, cool season or broadleaf spinach varieties are best grown when the weather stays below 75 degrees. The OSU Extension Service recommends the following spinach varieties as performing well in Oregon conditions, especially if planted when the soil is cooler. Savoy varieties have puckery, rather than smooth leaves.
Plant these varieties in spring for early summer harvest:
- (smooth leaf) Bloomsdale Long Standing, Olympia, Nordic IV;
- (savoy) Spinner, Correnta, Unipack 151, Melody, Skookum.
For late summer for fall and winter harvest, plant these:
- (smooth leaf) Oriental Giant, Rushmore;
- (savoy) Jive.
No matter where you are in the state, plan on planting broadleaf spinach about four to six weeks before your average last frost in the spring, and six to eight weeks before the first frost in the fall. From late spring until mid-summer, plant the heat-adapted spinaches.
Make sure your garden soil pH is between 6.5 and 7. Plant about 10 to 12 spinach seeds per foot, about 1/4 to 1/2 inch deep in nitrogen-rich soil. The rows should be about 12 to 18 inches apart. Thin spinach plants to about two to four inches apart to grow to their mature size, with leaves six to eight inches long, about six weeks after planting. Plants removed at thinning time can be used as salad greens. Unless your family freezes or cans spinach, 10 to 20 feet of row may be enough for a family of four.
For a continuous supply of spinach during the entire growing season, plant seed every one or two weeks. Sow cool season spinach in the early and mid-spring. Then plant the bolt-resistant variety Correnta in the late spring and through most of the summer. Then follow with more plantings of cool season, broadleaf spinach in the late summer and early fall.
Try planting heat tolerant green leafy spinach-like greens that aren’t related to spinach, but look and taste somewhat like spinach and can be used like spinach in the kitchen, including: New Zealand spinach (Tetragonia), amaranth (also known as “Hin choy” or Tampala spinach) greens and Orach (also known as mountain spinach or “Atriplex hortensis”). These spinach-like greens can be planted in the late spring and summer and thrive in the heat and don’t bolt as easily as true broadleaf spinaches.
Oregon seed companies that offer several varieties of spinach (including bolt-resistant variety Correnta) and spinach-like greens include: Nichols Garden Nursery, 1190 Old Salem Road N.E., Albany, OR 97321-4580, toll free 1-800-422-3985; and Territorial Seed Company, P.O. Box 158, Cottage Grove, OR 97424-0061, toll free 800-626-0866.