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The Art of Spinach Germination
Pre-sprout spinach seeds in your refrigerator before sowing them outside.
I never get good germination when I sow spinach in the summer for a fall crop. What’s happening?
Spinach is a cool season crop, there’s no two ways about it. If you start it in spring it will bolt (send up a flower stalk) as the summer heat comes along, and its shallow roots mean it’s also prone to stress during dry spells. You can combat these things with shade cloth and a good watering schedule, but with the onset of summer you should expect to say goodbye to the spinach.
Growing spinach as a fall crop is much more fun. Spinach is extremely cold tolerant and I’ve had crops survive through some of the recent years of polar vortices. It’s fun to brush off the snow and crack ice and know you still have greens in the garden. If you can get a fall crop established then there is a good chance you’ll have it all the way through winter and into the following spring.
The challenge with spinach is getting the seed to germinate in warm soils. You will get the highest germination rate if you plant spinach seeds around 50ºF (it can take a couple of weeks for germination to happen at this temperature). As the temperature increases, the germination rate begins to drop. Not everyone knows this, which is why many gardeners are disappointed when they sow their spinach outside at the end of August and experience poor germination.
There are two tactics to address this problem. First, knowing that your germination will be stunted by the warmer soil, you can overcompensate by sowing a lot more seeds! A better approach is to pre-sprout the seeds in your refrigerator before sowing them outside.
How to pre-sprout spinach seeds
1) Soak your spinach seeds overnight so they imbibe a lot of water.
2) Take a couple of layers of paper towels and wet them. Squeeze out excess water so the paper is damp but not dripping.
3) Spread the spinach seeds on the paper towel and fold in half to sandwich them.
4) Place the paper towel in a ziplock bag or sealed container and put in the refrigerator.
5) Once the seeds begin to sprout (just the beginnings of a little white spinach tail) then take them out and gently sow the seeds outside.
6) This process can take a couple of weeks, but check on your seeds every few days. Remove any molded seeds as you are checking them.
People tell me I need to start a fall garden in July and August, what’s that all about?
I’m afraid it’s true. I know that your summer garden will be at maximum chaos, but you need to take a step back and think about fall if you want to have a decent homegrown harvest for Thanksgiving. The reason for this is that June 21, the summer solstice, is already a distant memory. That means every day is getting shorter, and less daylight means less plant growth.
We have to start our fall gardens early to combat this ‘slow down’ of growth with the aim of getting close-to-mature plants as we head into the cooler, darker months. Quick growing things like lettuce and radish can get thrown down through September and still give a good harvest. Some things like carrots and beets will survive a mild-moderate winter, so a late planting means an early spring harvest. But the slower growing crops that need to ‘head-up’ to make us happy require some forethought. I’m mainly talking cabbage, broccoli and Brussel sprouts, which enjoy cool weather but not shock or deep freezes.
July through mid-August are the recommended months for starting your fall brassicas in this region, and you’ll almost certainly need to start these crops in protected conditions. The pest pressure and the high heat is simply not conducive to raising these slow-growing brassicas right out in the open, with harlequin bugs, cabbage worms, aphids and flea beetles all able and willing to cause serious damage. Having to start your own transplants about six weeks before planting them out in the garden is actually a relief, because if you’re anything like me you won’t yet have the space to plant them straight in the garden anyway. I like to start my seeds in the basement, where it is cool for germination, and then either put them under grow lights or in a part of my hoop house which gets late summer shade from a maple tree. You’re basically looking for a protected spot where they wont get fried or eaten.
When you are ready to put out your transplants, remember that brassicas are heavy feeders and will want a well balanced soil rich in organic matter to grow well. Planting brassicas after a nitrogen fixing legume crop like beans can be a good idea. Using floating row cover while the plants are still small is a good way to protect from late season pests, but that pest pressure should reduce as the days cool towards winter.
Learn more at sowtrueseed.com.
Chris Smith, the community coordinator for Sow True Seed—an Asheville-based company that specializes in open-pollinated, heirloom, and organic seeds—answers common gardening questions in this regular column for Smoky Mountain Living.