Winter Gardening in Tucson

A concept that sometimes needs to be reemphasized for the northerners, used to frozen winters, is that the vegetable garden is active all winter long in Tucson. We often get remarks like “but planting season is done right?” and of course it is not. We can grow something in the vegetable and herb garden any time of year. The winter season has only begun, and throughout that season, you can plant successions of crops. There are considerations though, and we are here to tell you what they are.

One of the unique problems in the cool season is dealing with cold snaps or frosts. We will go over what plants really need frost protection (most of the cool season crops need little or none) but remember that when covering any crops on cold nights, use cloth, and if possible, suspend the cloth over the plants so that the cloth isn’t touching them. Plastic isn’t the best insulation from cold weather, and radiation from the sky is said to intensify cold damage—something that clear plastic doesn’t protect plants from. Therefore, best practices are usually using cloth. The focus of this article is about standard vegetables and herbs—growing tropical shrubs and trees is out of the scope of this discussion, and we’ll deal with that subject on a later date.

Below are the general groups of crops that you may be growing in a standard vegetable and herb garden:

THE COLE CROPS
Cole crops are the plants in the genus Brassicaceae—and you are familiar with most of them: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi… These plants are mostly entirely hardy and will need no protection from frost. In fact, many of these crops see improved flavor with the frost.

LETTUCES
Lettuces vary in their frost tolerance, and for the most part, you can almost tell just by looking at them. The softer-leafed varieties will be damaged—the outer leaf edges will get mushy and dark. A simple cloth covering (make sure the covering isn’t touching the leaves) will prevent the cosmetic damage. But most of the time, even if you fail to protect lettuce plants, they bounce back. Their meristem (growing point) usually keeps making leaves and will often recover.

OTHER GREENS
Swiss chard, minutina, mache, spinach, orach, and sorrel are all totally hardy for our area. Chrysanthemum greens or shungiku is hardy to light frosts, but you might consider covering it to prevent any minor damage. Some of the finer-leafed mustards can get minor damage with a frost.

ROOT CROPS
Many root crops are also cole crops, and most of them are very hardy to cold. Radishes, carrots, beets, turnips, even some of the more exotic root crops like salsify and scorzonera, are all hardy to the frosts. Some root crops are actually summer crops and will suffer foliar damage (potatoes, sweet potatoes). These are more perennial-type crops and will either be dormant for the winter, or in the case of the more tropical species, keep trying to grow and get foliar setbacks with each frost. But they won’t die.

ARTICHOKE & CARDOON
Artichokes and cardoon plants are cool season growers. But they can suffer some cosmetic damage during the cold snaps. They are from a mild, Mediterranean climate. But they will keep growing regardless, even if they slow down a bit. It’s worth the effort to cover them only on the coldest nights.

COOL SEASON HERBS
Most of the cool season herbs are pretty hardy—cilantro, parsley, chervil, fennel, lovage, burnet…sometimes dill will have some damage on the tips from the harder frosts, but it’s minor. Your basil, however, will usually go down with the first frost. That’s because it is a warm-season herb. Sometimes basil plants perennialize in protected spots. If you are lucky enough to have such a microclimate, you may have basil throughout the season.

PERENNIAL HERBS
Most of these are hardy—some may take a short break in the coldest part of winter. Others may grow with more vigor during the cool weather. A few are frost tender and should be protected: frost tender herbs include lemongrass, Mexican tarragon (this is not a true tarragon but a tropical marigold),

ALLIUMS
Alliums are the onion/garlic family. Most types of alliums like the cool season (they usually go dormant in winter). But some types may show damage from frost on the tips. This is nothing to worry about. Onions won’t need protection in winter. Your bigger concern for alliums is ensuring good drainage. A note on bulb onions—most people find sets to plant in fall. But in late winter, sometimes you can procure onion starts—these are basically bare rooted green onions that you set out to plant. They still form full size onion plants by May or June, just like onion sets.

THE CHICORIES
This includes endive, radicchio, frisée, puntarelle, grumolo, escarole (the chicories come in a mind-boggling array of forms): these are all hardy. Sometimes older leaves may brown but this isn’t usually a worry.

CELERY & CELERIAC
Totally hardy—including the slim-leafed Asian varieties.

THE INBETWEEN CROPS
Many crops are neither summer nor winter crops but exist in the balmy between seasons—sweet peas, snow peas, borage, nasturtiums…these need protection. They can persist through the winter if protected from hard frosts, but you might find the vining peas might become difficult to cover since they grow vertically.

COOL SEASON LEGUMES
Fava beans, lentils, and garbanzo beans are grown in winter in Tucson. They are mostly very hardy plants—hardiness depends on the variety you choose, so watch for exceptions, but most of these crops are hardy to about 20°F and won’t need covering unless we get one of those catastrophic freezes.