Update on our palo blanco tree

It’s been a while since I talked about the palo blanco tree (Mariosousa heterophylla) in our front yard; my last update was almost a year ago (here). Since I do get asked about it now and then, I want to share some photos of what it looks like now:

As you can see, it looks fantastic. It’s been blooming for 5+ weeks now, with more flowers than ever before. Maybe because we had such a mild spring with plenty of rain?

Palo blanco (“white stick” in Spanish, not to be confused with palo verde, “green stick”) is a slow-growing acacia native to the Mexican state of Sonora where it grows on hot rocky slopes. The Ruth Bancroft Garden website has a nice write-up about it.

We wanted a desert tree that’s open and airy, with tiny leaves, and that’s exactly what we got.

Our palo blanco is planted in the larger of the two succulent mounds inside the front yard fence and provides very light shade from noon on.

As I mentioned, it’s been flowering more heavily this year than ever before. Unlike the more typical acacia flowers that look like pom-poms, palo blanco flowers are pale yellow catkins. They’re particularly showy later in the day when they’re backlit by the sun.

In Arizona, particularly in the Phoenix area, palo blanco is a popular street tree. No so here in California. Unlike palo verde, which is now available in many nurseries (typically the ‘Desert Museum’ hybrid), palo blanco is much harder to find. You may have to special-order it from your local nursery.

Be aware that in the nursery trade, palo blanco may still go by its original name, Acacia willardiana, or by Mariosousa willardiana (the genus Mariosousa was split off from the genus Acacia in 2006). The correct botanical name, at least at the moment, is Mariosousa heterophylla.

If you’re worried by the fact that this is technically an acacia and that acacias cause bad allergies, you may be relieved to know that this urban myth has been largely debunked. Acacias are insect-pollinated; their pollen is too heavy to be transported by the wind. True, there are people who are allergic to acacias, but they are few and far between. Acacias are easy scapegoats for allergy sufferers because their flowers are so visible. In reality, seasonal allergy symptoms are typically caused by wind-borne pollen. When your eyes start to itch or you sneeze uncontrollably, blame grasses or wind-pollinated trees like birches, cedars, or oaks – not acacias.

© Gerhard Bock, 2024. All rights reserved. To receive all new posts by email, please subscribe here.