Resources for Gardening in New Mexico

Words and Photos by Marisa Thompson

Nothing says late summer like a tomato. Let’s look at ways to make the most of the harvest, prepare for the inevitable first freeze, and set up for a fruitful 2021 growing season.

Whether you’re growing your own or buying them from local growers, there’s no debating that homegrown tomatoes taste way better than store-bought. That is unless you store them in the refrigerator. The naturally volatile chemicals (aka volatiles) that give tomatoes their bright flavors are prone to breaking down when temperatures drop below 55°F for prolonged periods. This is why we’re told not to store flavorful tomatoes in the refrigerator, which is usually set to around 40°F.

As nights get colder, watch for the first frost of the season. Go ahead and harvest green tomatoes before they get bitten by a near-freeze and turn to mush overnight. Last year, many New Mexico gardeners were caught off guard, missed their chance at a final harvest, and were devastated to have come so far and lost so much at the very end. The first freeze in 2019, which some may remember since it crept up so quickly, was October 11 in parts of Albuquerque and Santa Fe. Whether green or red, mature tomatoes, because of the amount of ethylene (a natural plant hormone) that they produce, continue to ripen after they’ve been picked. If there’s a chance of frost, it’s time to harvest—ready or not.

Once you’ve had your fill of fried green tomatoes and made a batch or two of green tomato salsa (I follow recipes for salsa verde and substitute green tomatoes for the tomatillos), encourage the rest to ripen by storing them with a few red tomatoes. To slow the ripening process and keep them green longer without refrigeration, check them daily and continually pull out the redder ones. The tomatoes that never ripen and turn red weren’t fully mature when picked.

As my NMSU research colleague, Dr. Ivette Guzman, says, “Tomatoes are a gateway vegetable.” Harvest a few ripe fruits from a plant you’ve babied (or tortured) all summer, and you’re hooked, just like the rest of us.

That’s not to say that tomato plants aren’t riddled with problems. If you’ve given up by now, you are not alone. Even the most successful tomato growers are familiar with the usual suspects—curly top virus, blossom end rot, stink bugs, and tomato hornworms, to name a few I’ve personally dealt with this year.

Next year, consider setting up a shade structure of some sort. Completely wrapping caged tomatoes with shade cloth can help in multiple ways. The cloth limits beet leafhopper activity; they’re the only known vector of beet curly top virus, which shows up with a variety of symptoms such as curled leaves (sometimes with purple veins), thickened and stiff leaves, stunted overall plant growth, and plant death (more common in seedlings).

If these symptoms are ringing bells for you, try controlling your winter weed situation to improve next year’s chances. Beet leafhoppers are known to overwinter on mustards, like London rocket (commonly known as mustard weed), and then jump over to the veggies in spring when their winter hosts wimp out. Weed ’em and reap.

Shade cloth may also reduce potential exposure of the plants to thrips that could be carrying tomato spotted wilt virus or aphids carrying alfalfa mosaic virus. All of these viral tomato pathogens are diagnosed every year in New Mexico. In addition to limiting exposure to pests and pathogens, it’s cooler and less stressful under shade. And there’s no need to worry about pollination problems under cover because tomato flowers are self-pollinated, and the yields on disease-free plants can be astounding.

Leave it to me to uncover one major drawback of covering tomato plants: If tomato hornworms get in there and start chomping away, in one weekend they’ll nibble away most of the leaves so that only the midribs are left, sticking out like sore thumbs. Of course, even tomato hornworms aren’t all bad. If left in peace, they transform into hawk moths, or sphinx moths—important native pollinators.

Have you seen fruits that have split open at the shoulder, exposing black mold? This problem isn’t entirely preventable because the cracking is usually caused by irregular watering during fruit development. If we’re lucky with a good monsoon season, overwatering is bound to happen. With 51 percent more sunny days than the national average, New Mexicans rarely complain about the rain. The trick is to notice the cracking and harvest early enough before they begin to rot.

Growing a good tomato is a process that can, for many growers, take years. As the saying goes, the best gardeners have killed the most plants. Hopefully, these tips can add to an abundant harvest this year and help bring forth many more to come!


NMSU Tomato Resources: From planting to cooking and every diagnosis in between, visit the Bernalillo County Cooperative Extension tomato page at

The NMSU Plant Diagnostic Clinic analyzes plant material for pathogens and environmental stresses and suggests appropriate control measures when available. Insect and weed identification services are also offered. The Plant Diagnostic Clinic accepts physical samples that are submitted and shipped from your county’s NMSU Cooperative Extension office (for free!).

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