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 out 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 25ºF lows and some will even survive down to 15ºF. 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 utilizing 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.
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.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.