Desert Flowers 2018 Part 1

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I've been taking photos of some of our desert flowers this spring.

April is time for the yellow legume trees to flower. We have two native species, which used to be called Cercidium floribundum and C. microphyllum. They have been moved into Parkinsonia, the same genus as a Mexican tree widely planted here, Parkinsonia aculeata. All are known as palo verde, which means green stick. They have tiny, rapidly-deciduous leaflets, and most of the year trees photosynthesize with their bark. These are some of the most widespread landscape trees here due to low water use and beautiful growth. I didn't manage to capture vistas of trees in flower, but in April one can see thousands everywhere.

P. aculeata has much brighter and larger flowers, but it is a rank-growing and brittle tree that breaks easily in our monsoon storms. Plus, our two native long-horned beetles prefer it to the native species. As a result, trees usually have weak roots, and blow over easily during storms. Unfortunately, P. aculeata is breeding with the native species, extending far out into the surrounding desert. Hybrids inherit the rapid, weak growth from aculeata. Sometimes hybrids have the smaller and duller flowers from the other two parents, and other times they take after aculeata.

I didn't take photos of mesquite flowers because they're extremely unspectacular.

All these desert legumes were used as food by people here. The dry pods of mesquites are sweet. Dried seeds of these trees look like shiny beans. They store well, and can be cooked like beans.

These photos show two hybrids as landscape trees, and two Cercidium microphyllum on my property.

Cercidium hybrid


Cercidium hybrid


Cercidium microphyllum


Cercidium microphyllum



Botanists have been hard at work changing names in the bean family so they can get their own names appended to the Latin binomials. The bean family Fabaceae was for years divided into three subfamilies based on flower shape: Fabaceae, with typical sweet-pea flowers; Caesalpiniaceae, with much more flat and open flowers, having very long stamens and pistils; and Mimosaceae, including acacias and mesquites, with tiny flowers in clusters. The Cercidiums were in Caesalpiniaceae.

Now Fabaceae is divided up into many other subfamilies. Genus Acacia at one time was used for plants worldwide. The type species was Acacia nilotica in Africa. Now only some of the Australian ones are called Acacia. African Acacias are now in genera Vachellia and Senegalia. This involved botanists moving the type species of genus Acacia to a different genus, and designating a new type species. To me this seems as fundamentally wrong as you can get from the perspective of the Botanical Code. The type species of a genus is supposed to be the defining species for the genus, and all other species put there should be closely related to it. Many botanists saw this strange name change as an offence against African botanists by those in more powerful countries.

The former New World Acacias have been renamed Acaciella and Mariosousa. Everybody I know still calls our local cat's claw tree Acacia greggii. I think mesquites are still legally in genus Prosopis.