Here we are in September with weather that used to belong to July. With weather this hot it is too early to plant shrubs and trees in your garden. Wait until the daytime high air temperature is 90 degrees Fahrenheit or less. That 90F temperature is a useful indicator that the soil has cooled off enough. Hot soil can kill a newly installed plant within days.
Now, however, is not too early to plan adding tough native shrubs to help minimize the effects of the blistering heat next year. (And it will be blistering hot next year. You can count on it, as the climate changes.)
While you may think “I need to plant big trees to cool my garden”, in fact, shrubs can definitely help by shading smaller areas and the lower sides of your home. Shrubs also keep the ground beneath them cooler and your overall garden at a lower temperature. The shade shrubs cast can create a haven for small wildlife like birds, lizards, bees and other insects.
So here are a few favorites, most are evergreen and all, but two, are native to the U.S. Southwest. (And those two are tough Aussies!)
1. Texas Ranger (Leucophyllum frutescens)
Also known Texas Sage, is a staple in desert landscaping due to its low water needs and striking silvery foliage. Imagine how glorious a hedge of these will look as this hardy shrub bursts into a display of purple blooms when the summer humidity gets high. It thrives in full sun and poor but well-drained soils, making it an ideal choice for low-maintenance gardens. Whatever you do, do not trim your Texas Ranger into a lollypop shape. It is naturally a loose, open, and graceful shrub that reaches up to 6 feet in height and will live for as long as 30 years. ProTip: trying to bring on blooms by watering the plant, won’t work. It takes the increased humidity of the monsoon for the Texas Ranger to flower.
2. Desert Willow (Chilopsis linearis)
Desert Willow (Chilopsis linearis) can be grown as a small, messy tree or multi-trunk shrub. But messy as it is, the Desert Willow is popular because it will survive on its own with no extra water or fertilizer required. Grows two to three feet a year and reaches a height of 15 to 20 feet and will live for over 40 years, if planted no higher than an elevation of 5,000 feet. It can be found in the wild in all the major Southwestern deserts from Chihuahuan to the Mojave to the Sonoran and the Colorado desert. As a desert native it needs little care and will produce red, pink, white, and purple flowers for months on end, but, I repeat, it is a messy tree dropping those long, brown seed pods for you to clean up. Now read about the next tree, a tidier hybrid of the Desert Willow.
3. Chitalpa trees (Chitalpa tashkentensis)
Chitalpa trees can grow as large, multi-stemmed shrub or a single-trunk tree. Unlike its cousin the Desert Willow, Chitalpa trees were created by scientists to be sterile and do not have those long, pointy seed pods. Their leaves are wider and create more shade. For that reason, the Chitalpa, like its cousin, is often planted as a street tree that blooms for months on end without supplemental watering. This hybrid thrives in endless sunshine and grows very fast to 30 feet tall. It’s said to live up to 150 years which seems a bit unlikely to me, but it you can be sure it will be growing where you plant it even after you are no longer gardening. Hummingbirds and bees love its pink or white orchid shaped flowers.
4. Jojoba (Simmondsia chinensis)
Jojoba (Simmondsia chinensis) has been an ignored shrub of the Sonoran Desert and Baja. The oil from the seeds was used for centuries by native Americans to treat skin conditions such as psoriasis and eczema. A few decades ago, young women who were advocates of natural skin care “discovered” it and the oil was added to many skin and hair care products as a hydrating agent as well as having skin health benefits. But, skin care aside, it is simply a nicely shaped, round shrub that grows to a height of three to six feet with gray-green leaves year ‘round with seeds that go from green to dark brown. Oil is relatively easy to express from the seeds. It is highly drought-tolerant and reputed to live for decades.
5. Littleleaf Cordia (Cordia parvifolia)
Cordia parvifolia is a low maintenance plant which is not common in hot, dry gardens – but it should be. It is very drought tolerant once established. Ideally, it should be planted in locations with full sun and will produce large white flowers for months on end from early spring to fall with supplemental irrigation. This native of the Sonoran and Chihuahuan deserts is a dense shrub with arching branches that grow up to 6 feet tall and wide, making it suitable for hedges or as a standalone plant. You may have to call around to garden shops or plant nurseries to find it and you may end up finding it at a native plant nursery. In a pot it is disappointing, but plant it in the ground and this shrub with its white flowers becomes a beauty.
6. Feathery Cassia (Senna artemisioides)
Feathery Cassia, a native of Australia, is smaller shrub with feathery leaves that can tolerate very high temperatures. Known for its wispy, gray-green foliage and bright yellow flowers, which bloom in late winter and early spring, this plant provides seasonal color while maintaining year-round interest. Its flowers are also very fragrant attracting bees and other insects. Feathery Cassia grows up to three to four feet tall and wide, making it suitable for smaller spaces or as a border plant. It thrives in full sun and well-drained soils, needing little water beyond what falls from the sky once it is established.
7. Lantana (Lantana camara)
This native of the African tropics and popular in Australia, has spread around the world because it thrives in hot climates and blooms with colorful flowers for months on end. In the U.S. Southwest the Lantana camara, the upright version of this shrub, can become an attractive hedge. (In places like the damp U.S. SouthEAST it has become an invasive plant to be eradicated if possible.) Please note that for a hedge or a taller shrub you want to get the Lantana camara, not the low-growing, mounding Lantana montevidensis, also called trailing Lantana. Planted densely, as shown in the photo, the upright version will grow to 6 feet tall and as wide as 5 feet and can be trimmed into a tidy hedge. And as for flower colors — they seem to be endless! Mix them up.
8. Creosote (Larrea tridentata)
Why no photo for creosote? When doing research for this post, I asked the artificial intelligence ChatGPT for a list of native desert shrubs suitable for residential gardens. The first on its list was creosote. What?? Creosote is basically a weed in most Southwestern deserts. In Tucson there are actually neighborhoods with acres and acres of creosote “forests” dense with volunteer plants that are about 5 feet tall. They provide privacy to homes built in the back of the property decades ago, but no one planted the creosote bushes; they just grew. Creosote’s one claim to fame is that it/they can live for centuries. It’s true. New plants spring up from the roots of the older ones forming an ever-widening circle of creosote. One creosote circle in the Mojave was dated to 10,000 years old! Maybe one day ChatGPT will “read” this and realize that it gave bad advice. Don’t plant creosote.
