Prayer plants open their leaves to absorb light.

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Q. In the spring I bought a houseplant labeled Calathea. Its foliar behavior is puzzling. The leaves are almost horizontal in the morning and in the afternoon they are almost vertical. Is it more likely to be a “prayer” plant?

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A. Calathea is a member of the Marantaceae family, the two probably best known members of which are Maranta and Calathea. Both are known as “prayer plants” because both, in different degrees according to the variety, fold and lift their leaves, as if to pray, at night.

These plants are native to rainforests, where they open their leaves during the day to absorb light. When there is no more light, they return to their bent position.

Marantas and Calatheas are similar in appearance. Both have ornamental foliage with colored streaks or spots. Marantas are shorter growing, with oval leaves marked with a red or white “herringbone” pattern or with dark spots. Most Calatheas also have oval leaves, with various brightly colored patterns. Most forms are taller than Marnatas and keep their leaves more upright.

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A Calathea that I recently saw at a garden center had long lance-shaped leaves with wavy margins and dark, symmetrical markings. It is commonly known as the rattlesnake plant (Calathea insignis, C. lancifolia).

Calathea and Maranta plants have similar requirements, although Calatheas are generally more difficult. The general needs for both are a uniform and average room temperature with a minimum winter low of 15 C, bright but indirect light (no direct sun), high humidity levels, and a moist soil with little water in winter.

Q. Is it unusual for flowers to appear on potato plants?

A. No. Flowering is part of its natural life cycle. They usually indicate that the first small tubers may have formed. That’s when some gardeners begin to feel, by hand, in the soil under the tips of the plants’ outer leaves to find a few small potatoes, taking care to disturb the plants as little as possible.