The Q&A Archives: Beginning Desert Gardening

Question: I was hoping to start gardening this fall. I've never been a gardener before. I want to plant some vegetables and herbs in a raised bed which I wanted to build this summer. Are there some tips that you have, especially for the hot southwest?

Answer: Almost every type of vegetable and herb will grow there, but you need to know when to plant them. There are two growing seasons, a cool and a warm season, when different crops thrive. I suggest preparing your soil by adding lots of compost and just get it ready for the cool planting season, which starts around late September or so with plants growing through April/May. The warm season planting starts in Feb/March and plants go until the heat, or some go through the summer. A rule of thumb for determing when to plant is that cool season crops are those which you eat the stems, leaves, and roots, such as salad greens, carrots, beets, onions, etc. Warm season crops are those which you eat the fruits, such as tomatoes, melons, peppers, etc.

To improve your soil, incorporate plenty of compost. In sandy soils, compost improves soil fertility, water and nutrient retention. In clay soils, it improves fertility and drainage. Add a 4-6 inch layer of compost and incorporate it about 12-18 inches deep. If you build raised beds, they should still be at least 12 inches deep. Fill them with a 50/50 mix of top soil and compost. You can use manure if it is well-aged (6 months) or you won't be planting until it has lost it's heat and decomposed. Each planting season, add more compost. Incorporate a balanced fertilizer (e.g., 10-10-10) or add organic fertilizers such as fish emulsion, bone meal, and seaweed/kelp. Follow package instructions.

As salts accumulate in clay soils, they impede water penetration. Gypsum is a soil amendment that helps sodium be dispersed and leached beyond the root zone. With our high pH soils, it isn't really possible to reduce the pH significantly or permanently. The addition of organic matter reduces it temporarily on a localized basis. Soil sulfur can do the same. Sulfur also acts the way gypsum does (but uses a different set of chemical reactions), so it isn't necessary to add both.

After planting, add a 1-2 inch layer of mulch. Mulch is great to help retain soil moisture, reduce weeds, and as it breaks down it provides nutrients to the soil. Any organic matter can be used as mulch. Try compost, bark, wood chips, straw, or pine needles. As it breaks down, dig it into your soil and add more.

University of Arizona Cooperative Extension has a free calender you can download with the best planting dates for all vegetables. Go to, input Title Contains: vegetable; Subject: Gardening/Home Hort, and Type: Publication. It will pop up a link. Also, there are a variety of related topics in the Southwest Regional Report Index that you can scroll through. Feel free to send another email if you have more questions. Good luck with your gardening!

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