Almost 80 years ago, in his revered Standard Cyclopedia of Horticulture, Liberty Hyde Bailey referred to crotons as coming in an "almost endless variety." They were popular conservatory plants way back then, but now we grow them on patios and balconies, in soil in our landscape beds, and indoors in pots, just as our great-grandmas did. We're surrounded by crotons, and the list of varieties has grown exponentially. They're everywhere.
Let's get some botany out of the way first. Crotons are in the genus Codiaeum, and from the huge and varied Euphorbiaceae family of plants. They're native to the South Pacific. When grown in tropical climates, most types are shrubs or very small trees. If we have access to large greenhouse spaces, we can overwinter them until our plants, too, grow to those large mature sizes.
Crotons need bright light to develop their very best foliar color. In fact, if we try to grow them indoors in dark surroundings, crotons will soon drop lower leaves and become spindly. New growth will be bright green and lack variegation. You have to have them beneath skylights or next to a south- or west-facing window for them to stay colorful. They grow best in loose, highly organic potting soil (no native North Texas soil, please), and they benefit from high-nitrogen, water-soluble fertilizer once or twice a month (more often while they're outdoors in the summer).
Crotons' leaf colors vary greatly, as do their shapes. Elongated oval leaves are common, but you'll also find varieties whose leaves are as twisted as corkscrews. Some are lobed and T-shaped, and others are extremely narrow, almost grassy.
Watch for crotons at your favorite nursery or garden center, even this fall. Before you buy, think about exactly where you're going to be putting your plant. Match its new home with the kind of lighting it's getting at the store. If you make abrupt changes, it will either start dropping leaves or the leaves will sunburn and turn crisp.
You can use just about any type of container for crotons, as long as it has a drain hole. Keep crotons moist at all times. When they wilt badly, leaves begin to drop. As time passes, your croton will eventually outgrow its pot. You'll want to choose the next larger pot size and move it on up. Ideally, the pot should be one-third to one-fourth the height or width of the plant.
Crotons can be rooted from cuttings, but you'll really need a greenhouse and a mist propagation bed to do so. The easiest way for home gardeners to start new plants is to air-layer them. It's tedious but not complicated. Your raw materials will be a sheet of dry cleaner's plastic, waterproof tape, two bread wrapper twist-ties, a sharp knife, a toothpick, rooting hormone powder, a bucket of water and sphagnum moss (not sphagnum peat moss).
Soak the moss in water for an hour or more. Once it's saturated, locate where you want the air layer to be on the plant. It should be on a vigorous stem, 7 or 8 inches back from the growing tip. Strip off two or three leaves to expose the stem. Use the knife to cut a thin sliver of bark away from the stem, but be careful that you don't sever the stem completely. You may prefer just to "wound" the stem by removing a bit of the external tissue, exposing the white wood beneath.
Dust the cut surface with the rooting hormone powder. You can use the toothpick to do so, and if you've left a flap on the stem, you can also insert a piece of the toothpick to hold the flap away from the stem.
Wring the moss until it stops dripping, then clasp a fistful of moss around the stem. Carefully wrap the moss in the plastic, making two or three layers as you do. Use the bread twist-ties to hold the plastic in place at each end, then seal the openings with the tape. If the air layer is too heavy and threatens to break the twig, tie a splint along the stem to support it.
Given six to eight weeks, your air layer should be showing roots through the plastic. At that point, you can cut the new plant away from its mother and pot it up individually. You may want to trim off a few inches of top growth to help the plant adjust, and put it in a bright but shaded location.
Here's hoping you'll include a few potted crotons in your landscape for the rest of this season and that you'll enjoy them indoors after that. Leave them out as long as you dare, but don't expose them to temperatures very far below 40. You may want to shuttle them in and out for a few weeks before bringing them in for the winter.
Neil Sperry publishes Gardens magazine and hosts Texas Gardening noon-1 p.m. Saturdays and 9 a.m.-noon Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.