It may be chilly outdoors, but Frosty ferns (Selaginella martensii) can provide a warm, inviting atmosphere when grown indoors during the winter. These plants are often sold during the winter holidays since their green leaves, tipped in white mimic frost on ferns. However, Frosty ferns are not actually ferns, but belong to the Selaginellaceae or spike-moss family and are native to tropical regions (Figure 1).

Figure 1 A Frosty fern plant with its green foliage tipped in white, which mimics frost on ferns.

Figure 2 A Frosty fern placed in a glass container with water and small pebbles in the bottom, which is used to maintain high humidity for the plant.

Most Frosty ferns are produced in greenhouses and are sold as four- to six-inch-tall plants, but can eventually reach up to 10 to 12 inches-tall. Although this plant thrives under greenhouse conditions, it can be a bit more challenging to grow in the average home. Frosty ferns grow best in partial shade at about 65 to 70° F, at least 70% relative humidity, and in moist, but well-drained, growing medium. Since most homes often have a lower humidity, especially during winter, it's best to place potted Frosty ferns in a tray or pot saucer containing water and about an inch of pebbles. The water will evaporate to create a more favorable environment for the plant and the pebbles keep the plant's roots from standing in water. To further elevate the humidity, a frosty fern can be placed underneath a transparent dome. For a snow-globe effect, set a potted Frosty fern inside a round glass vase (or terrarium) with pebbles in the bottom and seal the top of the container with clear plastic wrap (Figure 2).

To care for Frosty ferns, water them fairly often to maintain good moisture in the potting medium, but keep the roots above the standing water in the saucer or terrarium. Also, fertilize Frosty ferns sparingly, about once a month at about one-eighth the recommended rate for most indoor plant products. The frosty white appearance at leaf tips is lost when too much nitrogen fertilizer is applied. Plants obtained from reliable sources will seldom suffer from pests. Watering without wetting the foliage will prevent problems with diseases. Also, these plants are not poisonous if children or pets nibble on them.

When a Frosty fern becomes crowded, it can be divided, and each plant repotted. To multiple plants, simply remove a portion of the stem and place the cut end in a container of moist potting medium, water it, and seal within a plastic bag for rooting in about a week.