Many of us think of August as a time to harvest tomatoes. I’d like to suggest that August and September are also the ideal planting time for fall, winter and spring crops.
In our mild-weather valley, we can plant cool-weather vegetables as late as October. How lucky are we to be able to harvest fresh vegetables from our garden almost year round? Put in a few Bibb or Butterhead lettuce seeds now and 45 days later you will have plants that can make salads all winter long if you harvest a few outer leaves at a time.
Cool-weather vegetable gardens require much less attention than summer gardens. Because our rainy season coincides with our mild winters, soil dries slowly. Often, very little watering needs to be done.
Moist soil buffers the impact of any frost because the soil doesn’t get as cold as the air. Although most vegetables will not survive prolonged severe cold, cool-season crops will survive a few days of 25 degrees Fahrenheit lows and some will even survive down to 15 degrees F. The University of California keeps historical frost records that suggest that Napa has only a 10 percent chance of frost at the beginning of November. But the likelihood of frost rises to 50 percent in early December. You have plenty of time to plant now and have thriving plants before winter cold sets in.
Be aware that some cold-weather crops won’t grow much during the winter. Root crops such as carrots, beets, radishes and parsnips will hold at maturity in the garden until you are ready to eat them. It’s almost like having an extra refrigerator. Kale, cabbage and broccoli will grow slowly but do need to have a good start before the cold sets in.
When choosing cole family crop varieties (kale, broccoli, cabbage), note if they are labeled “early” or “short season.” These varieties are less hardy than those labeled as good for overwintering. Early-harvest varieties were bred for areas with winters too severe for vegetables to survive. They need to reach maturity quickly. Hardiness has likely been bred out of those plants.
Besides being able to harvest over a longer time, you will find another advantage to planting overwintering varieties of carrots, beets, spinach and kale. When these vegetables are exposed to frost, they undergo a process sometimes called cold-sweetening. The plant stores glucose and fructose to guard against frost damage. Sugar dissolved in a plant cell makes it less susceptible to freezing in the same way that salting roads reduces ice. So a little frost often makes these crops taste sweeter.
Many gardeners prefer to plant seeds for these crops directly in the ground. However, if you start seeds inside, you can pop the seedlings into ground that you are now using for a warm-weather crop, allowing you to make optimal use of valuable garden space. Local nurseries and garden centers will also have seedlings available.
Don’t forget to give your soil some extra TLC. Because you are using the soil year-round, remember to dig in fertilizer and organic matter more than just once a year. Twice would be good.
When deciding where to plant cool-weather vegetables, don’t overlook areas of your garden that are too shady in warm weather. The sun traverses a different path in the sky in summer and winter. So new planting areas may be available. Keep in mind that salad greens and leafy vegetables require only four hours of full sun every day.
I plan to add an extra-warm glow to my holiday meals by harvesting and serving vegetables from my own garden. Now that you know how easy it is, maybe you will join me.
Workshop: UC Master Gardeners of Napa County will lead a workshop on “Growing Winter Vegetables” on Saturday, Aug. 26, from 9:30- 11:30 a.m., at the C Cooperative Extension office, 1710 Soscol Ave., Napa. Soil preparation, sunlight and temperature requirements, when and how to plant, watering, fertilizing, pest management and harvest tips are the topics presented. Online registration (credit card only); Mail-in/Walk-in registration (cash or check only).
Do you want to become a UC Master Gardener of Napa County volunteer? To obtain an application you must attend one of the information meetings. For meeting dates, location and times or to learn more about the program and volunteer commitment, see our website.