Endangered Cactus Native to Nantucket

by Dr. Sarah Treanor Bois
Director of Research & Education at the Linda Loring Nature Foundation

Nature on Nantucket conjures up images of rolling moors and beach grass. Some may think about the wet forests of Squam Swamp or the sandplain grasslands along the south coast. How about cacti?

The heavy fog of the Gray Lady does not bring to mind succulents and spiny cacti. And yet, Nantucket is home to the only cactus native to Massachusetts. The eastern prickly pear cactus (Opuntia humifusa) is New England’s only native cactus. On Nantucket, the Prickly Pear is most common on Coatue and Great Point. You can find it in among the dunes and swales (and poison ivy!).

The eastern prickly pear cactus | Nantucket, MAOur prickly-pear is easily identifiable as the only thing resembling a cactus on Nantucket. It spreads along the ground and grows only about two feet high. It’s flat, fleshy pads (which are actually stems) are glossy green and ovate measuring up to six by four inches. The areolas (areas where spines are attached) have minute, barbed, deciduous spines that are arranged in diagonal patterns on the pads. The spines may be small, but they are barbed and can imbed easily, and annoyingly, into your skin and clothing.

Prickly Pear Cactus can be observed any time of year, though it is easiest to find in summer when the showy yellow flowers are present. In 1912, Winthrop Packard put it best when he wrote, “In April the prickly pear is as ugly as sin to the eye, with its lobster-claw growth, uglier still to the hand with its steel-pointed thorns, but later it will put forth wonderful yellow, wildroselike blooms in rich profusion, making up for all its dourness.”

The buttery yellow blossoms can be seen in abundance when flowering right at this time of year. The large flowers seem so exotic when discovered unexpectedly on your own and must be seen to be believed. These cacti are actually at the extreme northern limit of their natural range in Massachusetts.

It is an odd juxtaposition with our “moorland” species like false heather which seem more at home in northern climates. But as famed botanist Asa Gray once said, nothing in the way of plant life could surprise him on Nantucket.

The fruit of the prickly pear is fleshy and green initially, becoming pinkishred as it matures. The plant has been documented at Native American archaeological sites, presumably because of the sweet, edible fruits. The red fruit, which gives this cactus its name, is apparently juicy and delicious, though slightly sour, but do not go harvesting this plant. The prickly pear is now protected under the Massachusetts Endangered Species Act.

This special plant is not only unusual in its setting, but is listed as endangered by the Massachusetts Natural Heritage and Endangered Species Program giving it full protection in the state mainly due to available habitat.

Prickly Pear is currently known only from Barnstable, Dukes, and Nantucket counties. It is native in Dukes and Nantucket counties and thought to have been introduced to Plymouth, Middlesex and Barnstable counties. Prickly Pear was known to grow in coastal dune communities as early as the 1830s.

The open, protected habitat of Coatue and Great Point provide space and security for this rare species. After some severe winter storms, I have often walked along Monomoy shores with my son and dog, looking for treasure that may have floated up on the beach. Aside from the odd boat cushion or piece of lighthouse brick, we have found prickly pear pads multiple times that have just washed ashore from across the harbor. As this plant can establish vegetatively via detached pads as well as from seed, I was hoping to see a population arise on the shores of Monomoy. No such luck, however.

The prickly pear was one of the first plants of note on Nantucket making it into an official report in 1833. In 1961, botanist Frank MacKeever said that this 1833 report of our native cactus marked the “starting point of exact Nantucket botany.” While multiple botanists, naturalists, and plant enthusiasts have been obsessed with Nantucket botany ever since, we owe a debt of gratitude to the unique characteristic of the Prickly Pear cactus for putting Nantucket flora on the map.