Susan Waterman

July really isn’t too early to start envisioning your fall and winter harvest. If you are planning to grow cool-season crops for extended harvest or for the entire winter, consider starting to plant around August 1. Seedlings can be started in pots, then moved to locations where there will be extra protection, like a greenhouse, cold frame, covered raised bed or an outdoor garden that will be covered with frost cloth and/or plastic.

The advantage of starting to plant around August 1 is that the earlier seedlings will surely have an adequate amount of sunlight every day for strong growth and plenty of warmth to get a good start. It’s convenient to have plenty of seedlings on-site or in pots – extras won’t hurt – to remove or transplant, rather than to be short once the weather cools off and the days are short. In the event of an early fall, it’s entirely possible that seedlings started after the middle or end of September just may not take off, or germination may be very erratic. Remember that the “official” date for predicted first frost in parts of northern New Mexico is October 15. For most cool season crops, our winter day length is adequate for development to harvest if the seedlings are started in 7-8 hours of good light. On the other hand, it’s possible that the early sowings for cool season crops, especially for lettuce, kale, broccoli and chard, may require a little shade cloth to cool down the end-of-summer hot sun and to prevent bolting.

Examples of cool season crops to start in successive plantings every two weeks in August and September include, broccoli, kale, chard, spinach, radicchio, corn salad (mache), cauliflower, cabbage, mustard greens, lettuce (several varieties), green beans, radishes, carrots, beets, green onions, arugula, endive, peas, turnips, chicory and claytonia. Some cool-season crops are more sensitive to temperature ranges than others. Radicchio, for example, doesn’t develop when the low temperature end is too low or the high temperature too high. Spinach will bolt with a high end much over 70 degrees, especially in a greenhouse or covered frame. Turnips and mustard greens aren’t so sensitive to temperature ranges and will do well under many conditions. Kale is pretty easy as well, as is chard. If root crops like beets are planted on site when temperatures are low and day-length short, the roots may require lots of time (three months or more) to develop, and may become woody. But the greens can always be harvested.

If you haven’t experimented with kale and collards, I’d like to suggest trying these very easy-to-grow cool-season veggies for season extension and winter harvest. If you want to try planting out directly, plant the seeds by mid-August or at the latest, September 1. Kale (Brassica oleraceae) is perhaps the most cold-hardy of the cool season greens. Its flavor sweetens after one or two light frosts. Both the Dwarf Blue variety (curly leaf) and the Red Winter variety (smooth leaf) are very nutritious and cold hardy. You’re likely to have a nice harvest well into the winter, if not all winter long. And, kale seems to have the miraculous ability to resume growth after thawing from an overnight freeze that renders the leaves frosty and crisp! If the soil hasn’t frozen, kale will keep on growing. The tender young leaves may be used raw in salads, especially from the Red Winter variety. If you are experimenting, try drying some kale leaves, perhaps sprinkled with a little turmeric or chile powder. They make really tasty chips! And, both of my dogs love steamed kale as an addition to their meals – it’s a great way to use older leaves that become somewhat tough.

If you are planting your cool-season crops where crops have been growing all during the summer season, remember to rejuvenate the soil with some fresh compost and maybe a little organic food. In the case of the brassicas, popular cool-season crops, kale is one of the lighter feeders, a low-demand crop. Cabbage and Brussels sprouts will like more added nutrients, and broccoli and cauliflower even more. These crops will appreciate a lighter soil that is not compacted; soil that has adequate organic matter in it. All of the brassicas may be direct seeded in the August or early September. Also, try to plant in a rotation so that you are not re-planting the same family in one location after your summer harvest.

I wish you an abundant summer harvest and plenty of veggies in the fall and winter as well!

Susan Waterman has a Ph.D. in botany and over 25 years of experience in sustainable agriculture. For more info, visit Questions? Email

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