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New Mexico State University

New Mexico State University

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Microclimates Affect Gardens in New Mexico

LAS CRUCES -- Besides checking the map of growing zones, New Mexico gardeners need to know about microclimates, which cause gardens a few miles apart to produce very different vegetables.


In general, New Mexico gardens fall into one of three growing zones north, central or south -- based on the number of frost-free growing days. But the growing season's length can vary by 20 days within a zone because of microclimates.

"Microclimates or micro-environments in gardens are the result of variations in elevation, site exposure, soil type and air drainage," said George Dickerson, horticulture specialist with New Mexico State University's Cooperative Extension Service. For example, Alamogordo has a relatively long growing season, while Cloudcroft, just 20 miles away, has a very short growing season. Altitude differences cause the variance in length of growing seasons, Dickerson said.

The number of frost-free days determines which crops will grow, but it is possible to manipulate the growing season.

Valley orchards and gardens are more vulnerable to late frosts in the spring than gardens on a hill, because heavier cold air settles out in a valley as warmer air rises.

Apple growers will often use tall wind machines to mix the warmer air above with the colder air below to protect trees in bloom.

"If you want to get a jump on the growing season, use raised beds in your garden," Dickerson said. "Raised beds will warm up sooner in the spring than planting on flat ground, particularly if you run your beds from east to west and plant on the south side of the bed."

Gardens with a southern exposure warm up sooner in the spring than those with a northern exposure. Planting watermelons near a block wall with a southern exposure will get your melons off to a quick start in the spring. Heat absorbed by the wall during the day will be radiated back to the atmosphere around the plants at night.

In contrast, planting leaf lettuce on the north side of a house in the shade will help extend its growing season into late spring.

"Soil and ambient temperatures also can be modified by using various types of mulches," Dickerson said. "Synthetic black plastic mulches will help warm the soil in the spring and promote early growth of warm season crops like tomatoes. Preferred types are black plastic with pin-size perforations or woven plastics that allow water to penetrate and the soil to breathe."

Jars, bottles and hot caps can be placed over seeds and transplants in the spring to speed up germination or protect tender plants, though containers may have to be removed during the heat of the day for ventilation. Plastic sleeves filled with water that absorb heat during the day often are placed around tomato and pepper transplants during the spring to protect them from freezing at night and promote early growth.

"Row covers have also become popular as a way to promote early growth of plants during the spring," Dickerson said. "The best are woven polyester materials that warm the soil but allow rainfall to penetrate."

Row covers can be anchored down with fabric pins or soil and draped loosely over vine crops like watermelons. The fabric should be supported with wire hoops over single-stemmed crops like chile to keep the fabric from damaging the plants on windy days.