Most of us sow spinach directly in the garden in March or April for a spring/early summer harvest. However, as days become longer and temperatures rise, spinach starts to go to seed and is no longer edible. So we yank out the now-useless plants … and have to get along on frozen spinach for the rest of the season.
However, it’s also possible to sow spinach in August for a bountiful fall harvest.
There is just one catch, though: spinach seed germinates poorly or not at all at temperatures over 70 °F (21 °C). And in most climates, conditions are far hotter than that in August!
Start Them in the Cold
Luckily there’s an easy way out. You can pre-germinate (prime) your spinach in the fridge (spinach seed will germinate at typical refrigerator temperatures of about 40°F/4°C), then transplant it to the garden. Here’s how:
Place the seeds on a damp paper towel, then fold the towel in half to cover them. Now, slip the folded paper into a plastic bag and seal it, then put it in the refrigerator.
After a week, remove the seeds and sow them in the garden. In general, they’ll have already started to germinate! Having undergone a thorough cold treatment, they’ll now quickly grow to become full, luscious plants.
In addition, spinach is less likely to go to seed prematurely under the shortening days of late summer and fall, nor is it in the slightest bit harmed by the cooling temperatures of autumn. That means you can continue to harvest your spinach until severe frost finally puts an end to the growing season. In fact, in regions with mild climates, you can keep spinach growing right through the winter!