Cacti store water in thick fleshy stems, which is why they survive for weeks without rainfall.

The longer version

A cactus stem works as both a support and a water tank. Soft, spongy tissue inside expands as it fills after rain and shrinks slowly as the supply is drawn down, letting the plant keep going through long gaps between showers.

Several features reduce loss at the same time. A thick waxy coating slows evaporation, the pores open mainly at night when the air is cooler, and leaves are reduced to spines that shade the surface. Ribbed walls let the stem swell and contract without splitting as its volume changes. Together these traits let the plant treat rain as a deposit rather than something it must receive often.

Where this entry sits

Plants and Trees gathers ordinary and surprising details about how green things live, from the tallest forest giants down to the moss on a garden wall. Expect notes on flowers, seeds, roots, leaves, fungi, and the quiet tricks plants use to spread and survive. The full list sits on the Plants and Trees page, where every entry is listed in order.