According to a recent report from the U.S. Dept. of Agriculture, “Extreme drought conditions exist from Colorado Springs and Pueblo to the San Luis Valley and over most of the plains to the southeast of the big metro areas.”
If you live here, this isn’t exactly news. The fields are turning brown months early, wildflowers are small and sparse, and even the most aggressive weeds are wilting.
Living in the low-rainfall west, we’re used to gardening with minimal water. Xeriscaping is a household word, and basic principles of low-water gardening are widely available. (I’ve written several posts on it too—just type “xeriscape” into the search bar.)
The problem is that I want to grow veggies. Veggies aren’t exactly xeric plants. Most originate from parts of the world with considerably more rainfall than we’re getting here, so supplemental irrigation is essential. There are, however, some cultural practices we can apply to get the most food for the water.
As with most gardening advice, it all starts with the soil. I’m stuck with a combination of sand and silt, not the most water-retentive combination, but this applies to clay soils as well. Native Front Range soils average less than 1% organic matter, so amending with compost or other source of humus is critical. Add a couple of inches every year until you reach an optimal 5%. Too much causes a nutrient imbalance. Correcting your humus level allows your soil to retain moisture and keep it available to thirsty roots.
Next, growing in beds saves water. Widely spaced rows expose a lot of bare soil to the baking sun. Beds are planted more intensively, but every cubic inch of soil is used. The plants should be arranged so the leaves just touch at maturity. That way the ground is shaded, reducing evaporation.
Staying ahead of the weeds is essential for reducing water needs. Weeds compete with your crops for every drop, and usually the weeds win. One easy way to keep weeds in check is to apply three to four inches of mulch on top of the soil.
Mulch has the added benefit of adding another layer between your damp soil and the dry air. Mulches can reduce evaporation by as much as 70%. That’s a lot of water! I prefer straw as a mulch because it’s readily available and cheap, but you can use whatever you have at hand. Colorado State University has an excellent fact sheet on mulches. Just avoid using anything that won’t easily decompose in the soil if you plan to dig your bed next season.
How and when you water can also make a difference. Drip irrigation is much more efficient than sprinklers or furrows, and it helps prevent soil-borne diseases. Adding a moisture sensor to the system will keep it from turning on if it rains.
One of the most frequently asked questions I get as a gardener is, “How often should water?” And I always reply, “It depends.” A better answer is to apply enough water to wet the entire root zone. Then don’t water again until the top few inches are dry again (stick in a finger to see), or until the plants tell you they need a drink.
Plants talk if we can learn to listen. Bean plants fade from bright green to gray-green when they start to dry out. Squash leaves frequently wilt during the day, but perk up again at night as the weather cools. If they stay wilted, it’s time to water.
Finally, while no commonly grown vegetables are truly xeric, some plants use more water than others. Lettuce has big thin leaves that transpire rapidly, while carrots are deep-rooted and have ferny foliage with much less surface area. In fact, all root veggies are good choices. Cilantro and parsley also have tap roots, and many other herbs thrive on the dry side.
The good news is that our gardens are much more efficient water users than commercial farms. On our small plots, we can take the time to micro-manage our soil’s moisture content, and apply water exactly where it will do the most good. That’s just one more reason to grow your own right at home.