The wildflowers of the desert are some of the most interesting gardening plants available. If you can get these hardy soldiers started in your garden, you’ll have the pleasure of their company for decades. A few that work well together are datura, penstemon, agave, yucca and salvia. The contrasting textures and colors of these plants offer endless possibilities for the full sun garden. In part shade, try columbine and primroses.
Watch container-grown annuals and perennials for signs of water stress. Water containers once to three times a week, depending on the needs of the plants. Succulents in containers can be watered every two weeks deeply. Allow to dry out completely between waterings.
Established perennials of desert-adapted varieties should do fine with watering once or twice during the month of May if there is little or no rain. Cacti, agave and other native succulents should be fine with natural rainfall, but look for signs of shriveling or drooping branches in newly planted plants and water as needed. Don’t over-water or roots will rot.
Wait a week before watering newly planted cacti to avoid rot.
Deadhead annuals and herbaceous perennials to encourage more blooms. Mulch to conserve water.
Keep mulch thickly applied in the vegetable patch to conserve moisture and keep the soil from cracking. Apply a layer of compost, water deeply, then apply a layer of straw. Mulch can be tilled directly into the soil at the end of the season.
Warm season vegetables may be transplanted out this month, such as tomatoes, tomatillos, sweet potatoes, jicama and eggplant.
From seed, start squash, black-eyed peas, corn, cantaloupe and okra.
Basil and Mexican tarragon and oregano are great warm-season herbs.
Check the pH of your soil with a soil test kit and apply lime if the pH is below 6.5 for most vegetables.
Dig compost and other organic material into the soil before planting vegetables. Cottonseed meal or old sacks of cakey horse feed are good sources of nitrogen (don’t use medicated horse feed).
Plant sunflowers, marigolds and nasturtiums in the garden to attract pollinators.
Excessive pruning stresses plants. Prune only to remove dead or diseased wood or to train a young plant or enhance its natural shape. Never remove more than 25% of a plant in a year.
Prune Prickly-pears or Chollas after flowering. Cut only at the segment.
Allow your succulents to begin producing new stems and leaves as the temperatures warm before removing dead growth. Some tissue that looks like it was damaged during the winter may revive as temperatures warm and careful watering resumes.
Elephant trees will be producing new leaves and dropping old ones during the warm months. Wait until this process is finished to prune, if needed.
Mesquites will be putting out their catkins this month and next, so don’t prune until that process is finished.
Bermuda grass was introduced to the desert southwest as a lawn and pasture grass, and while it has become well adapted to the climate, it takes intensive watering to maintain a lawn during the growing season. If you want to remove a Bermuda grass lawn in favor of native grasses or other native garden plants, you can use glyphosate, which comes under the trade names of Kleenup and Roundup, among others. May is a good time to apply as the Bermuda comes out of dormancy and begins its growing season. Water the lawn daily for several days to encourage new growth, then, on a windless day, apply glyphosate with a sprayer according to the instructions on the label. Cover plants not to be sprayed with plastic. Repeat the whole process a week later.
When planting new native grass seed, make sure to till the area, apply some organic material such as compost, water deeply and roll the seed to make sure it has good contact with the moist soil. Then cover with a native grass hay (to keep seeds of invasives out).
There is a good description of establishing a native grass area at http://www.nm.nrcs.usda.gov/news/publications/SeedingNativeGrasses.pdf