Excerpts from Jim Conrad's
Naturalist Newsletter

ACACIA PENNATULA, leaves & flowering heads

from the June 7, 2015 Newsletter issued from Río Lagartos, on the north-central coast of Yucatán, MÉXICO

Among local trees that began issuing leaves and flowers well before the rainy season's first rain came is the feathery-leafed one shown above.

It's one of several spiny, feathery-leafed species we have here in the thorn forest that at first glance can be recognized as an acacia, mimosa or something close to them. The orange, spherical heads of tiny flowers look like those of Sweet Acacia, or Huisache, of which we saw so many in Texas. But, Sweet Acacia's twice-compound leaves bear much fewer tiny leaflets than this tree. In the picture, what look like the first divisions of a once-compound leaf are actually many very small leaflets (3mm, 1/10th inch), or pinnae, held close to one another. A close-up shows tiny individual pinnae of an older leaf with some pinnae having fallen off is shown below:


So, this isn't Sweet Acacia, but something close to it, and we needed to "do the botany."

ACACIA PENNATULA, flowering head

Above, you can see a flowering head close-up, with its densely velvety-hairy stem, or peduncle, and nearby leaf petioles. Breaking open a flowering head, we can see that each individual flower sprouts numerous -- more than ten -- stamens, just like the acacias, as shown below:


This is ACACIA PENNATULA, commonly occurring in Yucatan's arid scrub and thorn forests, and similar spots throughout most of hot, dry Mexico south through Central America into northern South America.

Acacia pennatula is a fine tree, one easy to distinguish from other similar, closely related species, even when it's not flowering or fruiting, because of its many minute leaflets and fuzzy young vegetative parts. Moreover, it's a handsome and useful tree, the wood often serving as building material and fence posts, burning well, and making good charcoal. The tree's high-protein legume-type pods commonly are eaten by livestock, and traditionally the bark has even been used in Mexico to treat diarrhea, which makes sense because the bark is full of puckery tannin.

Ecologically, the tree's spreading root system controls erosion, and the tree itself makes good shade, is frost-resistant and, as a member of the Bean Family, even fixes nitrogen for use by the rest of the biosphere.

One aggravating thing about the species is that it doesn't have a decent name. In English it's basically unknown, and Spanish speakers tend to use names already applied more widely to other similar-looking species. In many areas it's called Mesquite, but it's very different from real mesquites. It's also called Huizache, like Sweet Acacia, and there are other such names, but none just for this tree. The Maya have two names for it, Ch'i' May and K'ank' i Ilische', and even the experts have alternately assigned it to other genera, including Inga, Pithecollobium, Poponax and Vachellia.

It just shows you that you don't have to have a name to go about doing decent, benevolent things for the community at large.