Mesquites seem to have become the Street Tree of choice in some cities in the arid Southwest. Cities can line the streets with allées of Honey mesquite (Prosopis glandulosa) or Velvet Mesquite (Prosopis velutina) knowing full well that maintenance is not going to break the city budget. As natives these trees thrive in harsh, dry climates with almost zero upkeep. And Fall is the best time to plant them.
When you plant keep in mind that irrigating and fertilizing a mesquite is a mistake and planting one in a lawn that is regularly watered can be a disaster: the roots will be shallow, the tree will become top-heavy and topple over in the Spring and Fall windstorms.
A third native mesquite, the Screwbean (Prosopis pubescens) is more of a tall, thorny shrub and is best planted in an out of the way place. One Screwbean mesquite I saw not long ago was tucked back in a no-irrigation zone of a large Las Vegas garden where it and a nearby Desert Willow (Chilopsis linearis) were surrounded by a protective circle of agaves. A good choice of companion plants!
In addition to these three, other mesquites from Chile and Argentina have been introduced into the Southwest and have cross-bred like crazy with the locals. And thorns have turned up unexpectedly on supposedly thornless mesquites.
The problem with these fast growing, very drought tolerant trees is that they don’t give us colorful blooms in our gardens. Yes, yes — I know they “bloom”–after all, that’s where Trader Joe’s Mesquite Honey comes from–but the blooms are very subtle. Bees may notice them, but the average person driving along the street won’t.
So here are a few recommendations of trees to plant this fall that will produce colorful blooms in summer.
The first two I have already written about but are worth mentioning again.
The Chitalpa tree (Chitalpa x tashkentensis) was especially developed for low water usage gardens — by Russian scientists, no less. The “tashkent” in its name is the capitol city of Uzbekistan formerly part of the old Soviet Union where the scientists worked. Why those scientists spent time developing a ornamental garden tree–rather than a practical fruit or nut tree–I will never figure out. But I thank them.
Anyway…it is definitely a favorite because it blooms in pink, or white, or lavender for months on end in summer. It needs some watering, grows 2 or 3 feet a year and reaches a height of 25 feet tall. Bonus: hummingbirds love it.
The Crepe Myrtle (Lagerstroemia indica) can be a glorious blast of color in the summer, although be aware that it does need watering to do its best. A row of them behind our local library did not get irrigated this summer and failed to put on the usual bright show of flowers.
By nature the Crepe Myrtle is a shrub although some plant growers train them to be a small tree or standard. It tolerates neutral to slightly alkaline soil so be sure to add mulch around it at least once a year.
The Gold Medallion tree (Cassia leptophylla) is a Brazilian native that is now being planted in drought tolerant landscapes in the Southwest after being introduced to the U.S. by the Los Angeles Arboretum in 1958.
It flowers with huge basketball size clusters of yellow flowers at the ends of branches and the hotter the weather the more the blooms.
Happily, it also tolerates mildly cold weather down to 25° F for a short time. The City of San Francisco, of all places, is using it as a street tree and it is chilly there, for sure! The Gold Medallion tree needs soil that drains well and do not over-irrigate. It’s seeds are poisonous.
Now about Oleander…Yes, it blooms in summer, is drought tolerant, and grows fast. And every bit of the plant is poisonous–leaves, branches, flowers–everything. Seriously, it can kill people.
CLIMATE CHANGE
In the last few days many of us in the Southwest were blessed with rain. It soaked into the earth in some places and in other areas created flash floods. This rainfall came from the remains of Hurricane Sergio. As the Pacific ocean warms up along the California coast, we can expect more after-effects from hurricanes and, before long, full-fledged hurricanes actually blowing into Southern California and eastward. This year the water temperature off So. Cal. was 78° F. That’s 10° above the historic normal. The weather folks tell us hurricanes need 80° F water temperature for energy–and that’s only 2 degrees away. I look at the photos of the destruction caused by Hurricane Michael in Florida and hope we do not have to experience that here.
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