Although growing spinach in the spring or summer can be frustrating because of its tendency to bolt and go to seed, as well as attract aphids, growing it in the fall is an entirely different story.
Spinach bolts as our weather warms in the spring because lengthening days tell the spinach it's time to finish its life cycle and produce seed. A bit of logic will tell us to cooperate with nature and plant it when days are getting shorter.
Originally grown as a fall and winter crop in the Middle East, much of the world's supply of spinach seed these days comes from Washington's Skagit Valley. It is well suited to our mild Oregon winters but not to Rogue Valley summer heat and long days. But it nearly always survives our winters, with a little protection, and will provide fresh greens all winter.
Sow spinach seeds in your garden in September, when the soil cools a bit. If the soil temperature is 75 degrees or above, germination will be spotty; if it's over 85 degrees, it won't sprout at all. So use your soil thermometer to check before you plant. Another hint — keep the seedbed moist until you see second leaves.
Spinach planted in September will give you 3- to 4-inch plants before frost. After frost, the plants will not grow rapidly, but you can harvest them all winter. Use the small plants first, as you thin your crop. As you thin, gradually work toward a 6- to 8-inch spacing between the plants. More plants are lost to mold caused by poor air circulation than to cold. This method will help control that problem.
Because spinach does not grow rapidly in winter, you may want to plant more seeds than you think you need. That will also give you the option of harvesting by taking the outer leaves from the plants. As spring nears, you can cut the whole plant back quite severely, and it will grow again and feed you until March or later.
I find that, despite its ability to withstand cold, spinach needs a little protection in the really cold weather. A simple "hoop house" made of clear plastic over bent PVC pipe anchored on rebar "posts" works well. Be careful not to keep it too tightly closed when the sun shines, though, or you may get that dreaded mold if both the temperature and humidity are high. The hoop house will also offer some protection against four-legged pests such as rabbits and deer.
Spinach requires lots of nitrogen (we are growing leaves, after all), so some organic fertilizer worked into the planting bed is good. In January, a side dressing of blood meal will give it a kick in the pants for spring growth.
Hybridizing has given us many different spinach varieties, but they fall into two main categories, smooth leaf and Savoy (my favorite), which has darker, thicker, crinkled leaves. Some good Savoy varieties include Bloomsdale, Olympia, Avon, Spinner, Tyee and Giant Winter. New Zealand spinach, which is smooth-leaved, is not really spinach at all, but is close in texture and taste and is grown like spinach.
Many leaf-lettuce varieties and mustard greens can be grown the same way as spinach. Maybe you could add a few to keep the spinach company!
Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at firstname.lastname@example.org.