Mystery Plant! #728
By John Nelson
Let’s head to the beach! But watch out for the dune vegetation: in many places, the vegetation is protected by law, and visitors are admonished to stay off the dunes. Besides, some dune plants will bite you back.
Our Mystery Plant is one of the “prickly pears” native to the southeastern USA, known from the coasts of the Carolinas, Georgia, Florida, Alabama, and Mississippi, and it should be in Louisiana and Texas. It produces small but magnificent yellow flowers, followed by soft, red, seed-filled fruits, which technically are berries. Although the plants like to be at the coast, and commonly on and behind beach dunes, they are also found on sandy or rocky ridges and outcrops well inland, and away from the beach.
The cacti, of course, are plants that demand attention, for several obvious reasons. They are fascinating succulents with really interesting floral biology, and they usually characterize special habitats…dry ones. (But not always, and not just deserts.) Some species are tiny, whereas others are tree-like, such as the mighty saguaro of the American Southwest (whose flowers are pollinated by bats!). Cacti are commonly equipped with formidable hardware, in the form of spines, which, depending on the species, can be dangerous. There are nearly 2,000 different species of cacti, and they truly form an “all-American” plant family, occurring naturally only in North and South America. (Actually, there is one true cactus species that is apparently native to Africa. But that’s one out of 2,000.)
The spines of cacti (in fact, the spines of any plant) are modified leaves, which provide protection. Many cacti, certainly not all, have their stems flattened into characteristic “pads,” with the spines projecting from the individual nodes. Of course, spininess in cacti varies among species, and even as an effect of age, with older pads often eventually losing their spines. In addition to spines, some cacti, including this week’s Mystery Plant, and its relatives, come equipped with clusters of tiny, barbed bristles, called glochids. Glochids are often gold and shiny, but barely visible, on the surface of the pads. When these get into your skin, they will be there for a while, often causing serious irritation. With many cacti, it’s the glochids which are the problem, more so than the spines, and if you intend to handle cacti for whatever reason, you should use gloves.
Our Mystery beach-bum has mostly cylindrical pads which bear lots of really long spines, and these spines are SERIOUSLY barbed. Since the pads tend to be loosely attached, in a brittle sort of way, anything that touches those spines is going to readily dislodge the pads. Your crocs or flip-flops will do this easily: it’s almost like the pads are just waiting for you to show up, and once they are attached, you won’t soon forget it. Actually, the cactus has evolved this as a way of spreading itself, as any dislodged pad is very likely to take root as soon as it can, there on the dune: so watch your step.
[Answer: “Beach prickly-pear,” Opuntia pusilla]
John Nelson is the retired curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or email email@example.com.
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