Many gardeners in northern states wait until mid-May or Memorial day to begin planting their vegetable garden. That’s typically when we can expect the last spring frost to occur. But if you wait until then, you’re missing out on many easy-to-grow, frost-tolerant leafy greens. By the time spring rolls around, I’m anxious to plant kale, lettuce, Swiss chard, spinach, beets and bok choy. They’re nutrient-rich edibles that grow well in the spring and again in the fall when the weather is cool.

Soil Temperature is Key

In our garden, planting cool-season edibles takes place long before late May when I turn to heat-loving tomatoes, peppers and squash. Gardeners often rely on the calendar to decide when to plant. However, I use an inexpensive soil thermometer. That’s because the seeds of leaf lettuce can germinate when the top inch of the soil reaches 41 degrees F. Spinach seeds germinate when the soil reaches 50 degrees. You can find soil thermometers (digital and manual) online and in many garden centers. And while a thermometer is nice to have, once the daytime temperatures reach the 50’s, the soil is usually ready for sowing greens.

Shade-Tolerant Edibles

Unlike tomatoes and peppers, cool-season greens can be grown in semi-shade and in containers. I sow seeds of Black Simpson leaf lettuce and spinach each spring in a north-facing window box, in pots near the house, and in a recycled wheelbarrow. All of my planters hold soil-less potting mix that provides vermiculite and slow-release fertilizer. A watering can with a gentle spray moistens the top inch or so of the potting mix. You can sprinkle the seeds thickly across the top. I pat the tiny seeds in lightly–they should be very near the soil surface. I crumble a fine layer of potting mix just to barely cover them and give them a quick spray of water. In about 6 to 10 days the seeds will sprout. Once the leaves reach four inches or so, I use scissors to harvest several of them for a salad. The lettuce and spinach quickly send up new leaves so you can cut the plants several times before the weather gets warm and the plants are finished.