Excerpts from Jim Conrad's
Naturalist Newsletter

from the August 31, 2007 Newsletter issued from Sierra Gorda Biosphere Reserve, QUERÉTARO, MÉXICO

Along the gravel road skirting the reservoir a small tree is fruiting. Any North American familiar with hackberries would see the tree's resemblance to them, but there's one easy-to-see feature that makes a Northerner scratch his head: The tree's stems bear small, backward-curved, very sharp spines. You can see the spines, yellow-orange fruit and leathery leaves below:

CELTIS IGUANAEA, Iguana Hackberry

The species really is a hackberry, by which I mean that it's a member of the genus Celtis. It's CELTIS IGUANAEA, called Iguana Hackberry in English, and I can only guess what it has to do with iguanas. Five hackberry species are listed for the Reserve. The Flora of North America lists six hackberry species for North America north of Mexico. The US Southeast's Sugarberries are hackberries.

In North America Hackberries are often misidentified as elms, and one explanation for that is that they're in the same family, the Elm Family, so they do share similarities. However, there are easy-to-see differences between the leaves of the two tree-types.

Mainly, in the above picture notice how in hackberry leaves the lowest two side-veins arise from the midribs exactly at the blades' bases. This gives the impression of hackberry leaves being "three-veined from the base," like a three-fingered hand with webbing between the fingers. Also, teeth on hackberry leaf margins are usually irregularly spaced, few or absent, while on elm leaves teeth are many and regularly spaced. Fruits of the two trees are very different, elm fruits being like papery wafers while hackberries are cherrylike drupes. Typically flesh so thinly covers a hackberry fruit's seed that, even though the flesh may be a bit sweet, it's hardly worth the effort to pick them.

Another interesting feature of our Iguana Hackberry is that it's one of those trees acting as if wants to be a vine. Along the reservoir road it usually looks like a regular small tree but sometimes bigger specimens start leaning onto other trees, sending slender branches through them like a vine held in place by those spines.