Thin Air Harvest Practical gardening for the high, dry West

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Soil and water in a semi-arid climate

Alkaline and clay soils, drip irrigation, mulch that stays put, xeriscaping, and lawns sized for the water you have.

By the Thin Air Harvest editorial team. Updated November 1, 2026.

Most garden failures in this region that get blamed on “bad luck” are soil structure, soil chemistry, or water in the wrong amount. The climate sets the terms. The Colorado Vegetable Guide describes the state as semi-arid, with average annual precipitation near 15 inches and about 80 percent of that falling between April 1 and September 30, often as heavy downpours. Between storms the air is dry and, in spring, windy. A soil that cannot take water in, or that seals after the first shower, wastes both the storm and the irrigation you add later.

Chemistry comes before recipes. Large areas of the Front Range, the Wasatch Front, and the high plains are calcareous. pH above 7 is normal, and pH above 7.5 is common enough that CSU Extension’s iron chlorosis guidance treats it as the usual setting for the symptom. In those soils iron is often plentiful and still insoluble. New growth turns yellow between veins that stay green. Adding more iron sulfate without changing the conditions that lock iron up is a short disappointment. Elemental sulfur is a weak tool when free lime is high, because the carbonate buffer is large and irrigation water may be alkaline too. The alkaline soil page walks through what a lab report is actually telling you, and why blueberries, azaleas, and pin oak are the wrong argument to pick.

The lab to use is a land-grant soil lab, not a jar of vinegar at the kitchen sink. Colorado State University’s Soil, Water and Plant Testing Laboratory is the in-state option for Colorado gardens. Utah State University runs an analytical lab used by Utah gardeners. A basic test that reports pH, salts, organic matter, and sodium tells you whether you have a calcareous clay, a salty spot, or a sodium problem. Those three are not interchangeable. Gypsum, calcium sulfate, is a response to sodium. It is not a general softener for every sticky Front Range subsoil. Buy it after the test shows sodium, not because a video said clay needs it.

Texture is the other half. Clay holds nutrients and holds water, and it is brutal when worked wet. A footprint in wet clay becomes a brick that lasts all summer. The clay page is about timing, organic matter, and beds you do not walk on. Raised beds, covered on the vegetable side at raised beds, are a structure answer: you garden in a mix you can keep open, while roots still have a path into the ground below if you leave the bottom open. A bed boxed onto an impermeable caliche layer with no way out becomes a bathtub. Dig a test hole and fill it with water before you build.

Water delivery should match the planting, not the hardware aisle. Vegetables want steady moisture in the top foot while they are sizing roots and fruit. Established penstemons and blue grama do not. Putting both on one sprinkler valve is how xeriscapes drown and how tomatoes get irregular water and split. Drip or soaker lines on a separate zone, checked with a screwdriver or a soil probe rather than a clock, are the subject of the irrigation page. The page does not print a universal “one inch a week.” Evaporation on a windy June day in Pueblo is not the same as a cool week in Bozeman, and local utilities publish the schedule that matches their delivery system.

Mulch is how you keep the water you applied. It is also how you grow a vole problem or donate your straw to the alley. Light mulches move. Wood chips that have started to knit stay put better. Gravel stays put and then cooks the soil and feeds nothing. Keep every mulch off trunks and woody crowns. The mulch page sorts those choices by season: summer mulch for moisture, winter mulch applied after the soil freezes so it insulates cold rather than inviting growth.

The design system that ties this together was named in Denver. Xeriscaping, coined by Denver Water in 1981, is seven practices in the utility’s handbook: plan and design, soil amendment, efficient irrigation, mulch, plant zones, alternative turf grasses, and maintenance. It is not a gravel yard with a single yucca. The xeriscape page turns that sequence into a yard, and the renovation page turns it into a materials list you can price. The lawn page is the turf piece: buffalo grass and blue grama in full sun on the high plains, and a poor choice in shade or at a timberline cabin. The drip parts page is the first valve, the filter, and the regulator, not a slogan about saving water. Shrink the lawn to the shape you walk on. Water that shape. Let the rest of the yard go semidormant in a dry August once it is rooted.

Rainwater sits under water law, not just under a gutter. Colorado allows a narrow residential use: generally two rain barrels, combined capacity 110 gallons, rooftop water, outdoor use on the same property, under section 37-96.5-103 of the Colorado Revised Statutes as explained by the state engineer and by CSU Extension. That is a supplement for containers and a new bed, not an irrigation supply for a lawn. Other states in this region write the rule differently. Do not export Colorado’s barrel allowance across a state line. Ask the state water agency before you bury a tank.

Read the soil test article first if you have not tested. Read xeriscaping before you draw a plan. Read drip and mulch before you plant the plan. The plant lists live in the next section, and they assume this one has already been taken seriously.

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