A Cactus Grows in Rye
—Courtney Turner, Environmental Educator
Opuntia humifusa, Eastern prickly pear or devil's-tongue. Photo: prariemoon.com
As we enter September with daytime temperatures reaching 90 degrees, I find myself thinking about the tenacity of cacti and all the plants that survive day after day, month after month, in scorching, inhospitable climates. While I feel ready to wilt in such heat, cacti stand erect, having fortified themselves over centuries to endure extreme temperatures, the harsh rays of the mid-day sun, and the absence of water and nutrients.
We may think of cacti as exotic and relegated to faraway locales in Africa, Australia, or even the American Southwest, however, New York state is, in fact, home to one cactus--the Eastern prickly pear, or Opuntia humifusa. This plant is the only cactus native to New York and can also be found throughout the Eastern states, ranging from Florida north to Massachusetts and as far west as Texas and Montana. As you might imagine, the prickly pear grows in areas with desert-like conditions--full sun and dry, sandy soil--however, it requires special adaptations to cope with both hot summer days and the cold Northeastern winters.
Nearly every plant in the cactus family are what are known as succulents, meaning that they have thickened, fleshy parts that store water (consider the texture of an aloe vera plant). Most cacti store their water in enlarged stems and it is the stems--not the leaves--that perform photosynthesis. The cactus stems shoulder the burden of food production because most have adapted without true leaves, instead displaying spiky protrusions called spines. These spines are effective at fending off hungry herbivores and, due to their limited surface area, keep the amount of water lost to evaporation at a minimum.
Opuntia humifusa preparing for winter.Photo: Courtney TurnerBut how does the Eastern prickly pear survive our New York winters, with frigid temperatures and all that snow? As temperatures begin to drop in the fall, the modified stems of the plant, called "pads," go into hibernation-mode, drying out and shriveling up until they appear dead. If they did not do this, water stored inside the pads would freeze and expand, destroying the plant from within. A covering of snow keeps the deflated cactus insulated, maintaining a temperature just below freezing throughout the winter. Come spring, the pads will rehydrate and prepare to make new flowers.
The next time you visit the Rye Nature Center, stop by our garden where you can find these strange beauties growing and--if it ever cools off--preparing for winter.
