Here in the hot, dry region of the U.S. Southwest tree planting has become more urgent as year after year the days get hotter and drier. The driving idea behind the tree planting efforts is to create a green canopy, a natural, cooling umbrella over cities.
In Las Vegas, the Mayor’s goal is to have 60,000 new trees planted by 2050.
In Tucson, the mayor is more ambitous: she wants to see a million new trees planted by 2030. El Paso, too, has set a million tree goal.
And In Los Angeles, one volunteer group, City Plants, installs 20,000 trees for free along the city streets every year. (More about free or almost-free trees in Western cities in my next post.)
If you want to do your part, but on a personal, residential scale, consider planting one or more of these trees–plus one shrub, the Chaste tree. Many are as wide as they are tall. They are all drought-tolerant and cast shade to cool your home and garden. I’ve added information about how tall the tree should grow, how fast it will grow and how long the tree should live. (Hint: All but one should outlive you!)
Trees that bloom in the Spring and Summer
Sweet Acacia (Vachellia farnesiana) is a species of thorny shrub or small tree. Brilliant yellow ball-like flowers, which are used in perfume industry. Will grow to 20 feet tall x 20 wide, moderate to fast grower. Lives 20 to 30 years.
Palo Verde (Parkinsonia florida) is a native to the Sonoran desert and is recognizable by the green color of its trunk and branches. Almost leafless most of the year, so it casts only a light shade. It bursts into brilliant yellow bloom in April. Grows 2 or 3 feet a year to 15 to 30 feet tall with an umbrella-like canopy. Lives 100+ years.
Desert Willow (Chilopsis linearis) can be grown as a small, messy tree or multi-trunk shrub 30 feet tall. Grows 2 to 3 feet a year. Lives from 40 to over 100 years, if planted no higher than an elevation of 5,000 feet. As a desert native it needs little care but, I repeat, it is a messy tree dropping those long, brown seed pods for you to clean up.
But read about the next tree, a tidier hybrid of the Desert Willow…
Chitalpa trees (Chitalpa tashkentensis) can grow as large, multi-stemmed shrub or a single-trunk tree. Unlike its cousin the Desert Willow, Chitalpa trees were created to be sterile and do not drop those long, pointy seed pods. For that reason the chitalpa is often planted as a street tree that blooms for months on end. Loves the endless sun shine and grows very fast to 30 feet tall. And is said to live up to 150 years.
Trees that turn color in Fall
Fan Tex Rio Grande ash has leaves that turn to a brilliant gold in fall, unlike it’s cousin, the ordinary Arizona Ash (Fraxinus velutina) that lacks the golden yellow fall color. Both ash varieties are adapted for a desert climate with low water usage. It is moderately fast-growing tree that will grow to a height of 30 to 50 ft and may survive 50 years with proper care.
Chinese Pistache (Pistacia chinensis) is a pistachio hybrid that produces no nuts. In Fall the leaves on the male tree turn from green to gold to brilliant red then loses those leaves in winter. The female tree simply turns golden — not vibrant red. Grows 12 to 15 inches per year to a mature height of 25 to 40 feet tall and as wide. Should be planted in full sun; if planted in partial shade the result will be a lopsided tree.
Trees that need little maintenance
Mesquite (Prosopis velutina) commonly known as velvet mesquite, grows 12 to 24 inches per year to a mature height of 40 feet tall. Needs almost no care. It’s advisable not to plant it in a lawn that is regularly watered. Too much water or fertilizer weakens the roots of the mesquite which may then tip over during high winds. It will live for as long as 200 years. Equally durable in a desert garden are the Honey mesquite, the messy Screwbean mesquite and Chilean mesquite which has fewer thorns.
Chinese elm (Ulmus parvifolia). Capable of adding 12 to 36 inches of height per season, the drought-tolerant Chinese elm is a very rapidly growing tree with a weeping shape and deep shade underneath. Some lose their leaves in winter and others do not and it is not clear why this happens. This tree can grow to a height of 40 to 50 feet within 15 years. Lives 50 to 100 years.
A tree that produces fruit
Fig tree (Ficus carica) The common fig tree is a deciduous tree that can also be grown as a shrub or espaliered on a trellis. Produces fruit in 3 to 5 years. Grows 12 inches a year up to 30 feet tall and in its tree form ends up much wider than taller. Its large leaves cast very dark, cooling shade and a fig tree lives 50 to 200 years. For other fruit trees for the desert go here.
And my favorite shrub, the fragrant Chaste tree
Chaste (Vitex agnus-castus) is a hardy, fast-growing flowering shrub that produces bloom spikes of light purple, white, or blue flowers in mid-summer. If seeds and faded blooms are removed it will continue to flower. It has very fragrant leaves. Grows rapidly to a height of 20 feet — the size of a small tree–and lives for 15 to 20 years.
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One thing I found out about the Chinese Pistache tree is that it can be male or female. Mine was in the ground for several years but only ever turned gold in the fall, never red. I was bummed because that is why I bought it in the first place. After some research I found it is only the male tree that turns color, and the nursery never mentioned that as a possibility. The female, which is what I have, has flowers here and there in the upper branches, in the spring. I read they can become become berries for the birds in the fall, but only if there is a male tree close, which hasn’t happened yet. It’s a beautiful tree now, quite large and providing lots of shade, but it will never have that fall color. So, whenver I see articles like this, I like to point it out, since it’s rarely mentioned.