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Medina River Greenway

There are many differences between Vachellia farnesiana (Huisache) and Vachellia schaffneri var. bravoensis (Huisachillo) other than the obvious differences in fruit, although noticing these differences requires some attention to detail.

The most reliable way to distinguish these two taxa besides the fruit is examination of the leaves. V. farnesiana has a petiolar gland that is partway down the petiole from the most basal pair of pinnae, meaning there is a noticeable gap between the lowest pair of pinnae and the gland on the petiole. And the petiolar gland tends to be small, not prominent (raised), and doesn't really stand out in coloration. By comparison, V. schaffneri var. bravoensis has the petiolar gland immediately adjacent to the most basal pair of pinnae (no gap present), the gland is usually also slightly larger, prominent, and is more noticeable due to its red coloration. These traits are visible in the first photo of this observation.

V. schaffneri var. bravoensis also tends to be smaller to much smaller than V. farnesiana at full maturity, the inflorescences tend to be somewhat more yellow (yellowish-orange rather than orange), the twigs tend to have a minor zigzag habit, the nodes tend to be more swollen/enlarged, the leaves tend to have less pairs of pinnae on average and the pinnae sometimes are slightly recurved (bent backwards), the paired spines are slightly different and often noticably sharper to the touch, and the flowers have a slightly different scent than V. farnesiana - more complex and even more pleasant than V. farnesiana. Hopefully you noticed all the "tends to" and "often" in this description rather than speaking in absolutes. It is more reliable to identify these taxa based on the petiolar gland characteristics than all the aforementioned traits put together.

Phyllaries united most of their length (nearly to apex); ring of oblong-orbicular glands on phyllaries; alternate leaves.

Compare with https://www.inaturalist.org/observations/138642876 to see morphological differences in involucel between this and T. pentachaeta