A lush bed of garden spinach will bring joy to any gardener, but spinach planting dreams don’t always come true. In my experience, the biggest challenge comes up front, when you want spinach seeds to germinate all at once, like little soldiers. Sometimes I get uniform sprouting, with rabbit-eared seedlings at just the right spacing for easy thinning. But more often I’ll see gaps in rows, and spotty germination often plagues my indoor flats, too. Whether I’m starting a few spinach seeds early indoors or sowing them in the garden in spring and fall, I’ve learned to watch every detail in order to get garden spinach off to a strong start.
First let me back up a bit to address starting spinach seeds indoors, which is well worth doing in later winter. Contrary to proclamations that spinach is untransplantable, I find that young seedlings with two true leaves are as easy to transplant as any veggie as long as you do everything you can to prevent stress to your little spinach plants. In my garden, this means having a rich bed ready and waiting, covered with a plastic tunnel, glass window frame, or other protective enclosure. Using spinach seedlings helps stretch the spring season, so that I’m harvesting garden-fresh spinach before the last frost passes.
Although spinach germination can proceed (very slowly) at temperatures near freezing, spinach seeds sprout best at 60-68°F (15-20°C) – yet another reason to start your first garden spinach of the year indoors. As the weather warms in spring, you can direct-sow a second planting. In spring I like to alternate spinach seed with pinches of faster-growing lettuce, which can be pulled as the spinach needs more room to grow. You can also alternate rows of spinach with onions, which make good garden companions. Upright onions don’t crowd the spinach, and the spinach helps shade out weeds between rows of onions.
Priming Spinach Seeds
Many references say that spinach seed is good for three years, but I won’t stake the success of a planting on a reference chart. I draw the line at two years, which means I buy one or two packets of fresh spinach seeds every spring, and compost seeds more than two years old.
Even so, I have found tremendous variability in the germination rates of spinach seed from various sources, or it could be me. Like all seeds, spinach germination takes place in three stages: soaking up moisture, growing new cells inside the seed, and finally the emergence of the radicle, or sprout. Several studies have shown that spinach germination rates are higher and more uniform when the second stage is prolonged a bit, in an oxygen-rich atmosphere, before the seeds move on to a full sprout.
Scientists call this process "priming," and it’s easy to do at home. About a week before planting, soak spinach seeds in room temperature water for 24 hours. Place the wet seeds on a paper towel, and allow to dry at room temperature for a day or two. Shift the seeds to an airtight container, and keep in a cool place for up to a week. The primed seeds will retain enough moisture to complete the first two stages of germination. After planting, primed spinach seeds germinate in only 5 days, compared to 10 or more for seeds straight out of the packet.
Getting a good stand comes down to spoiling your garden spinach, and the same tricks to promote spinach germination in spring come in handy in the fall. Spinach loses its enthusiasm for sprouting at temperatures over 75°F (23°C), so I prime a few seeds before starting them indoors in August, and direct-sow a winter crop when temperatures cool down in autumn. For a vegetable that’s as delicious, versatile and nutritious as garden spinach, four plantings a year is not too many.
By Barbara Pleasant