Facts About Ferns

Ferns are one of our most interesting non-flowering plants suitable for indoor or outdoor use. Their history goes back at least 400 million years, even before the age of dinosaurs. They existed at least 100 million years before the first flowering plants developed. Ferns can be used to create a naturalistic feeling indoors, and we are lucky to have a few that are tolerant of the conditions inside the average home. There are nearly 12,000 species of ferns, but only a few of these make good houseplants.

One of the most suitable and popular of all ferns for use indoors is the Boston, or sword, fern. It produces long, graceful fronds — leaves — that cascade over the pots. The fronds of the Boston variety are fairly long, each one reaching up to 3 feet in length. It was first found in 1894 and became the most popular fern of the Victorian period in America. Many variations and selections from this same fern species have appeared over the years. Whitman fern is more compact with leaves no more than 18 inches in length. Fluffy Ruffles has only 12-inch-long leaves with dense bipinnate leaves. The Dallas fern is a patented variety that also has fairly dense growth and is more tolerant of lower humidity than most other varieties of this same species.

Another interesting fern for the home is the bird’s nest fern. Its fronds are not divided into small segments as is the Boston fern and its related varieties. These leaves are large, long and narrow, coming from a rosette center that forms a symmetrical “nest” or bowl-shaped plant. The leaves have a more leathery feel and are fairly tolerant of low humidity. It grows best with a little more light than the Boston fern. It should have fairly constant moisture at its roots but can endure drier conditions than most other ferns.

The holly fern has dark, glossy green leaves. The individual leaflets of the fronds are fairly coarse, but each one has a crinkled margin that gives the illusion of English holly leaves. Like most ferns, it needs fairly cool house temperatures at night of about 55 to 60 degrees. It is not tolerant of drying as is the bird’s nest fern.

There are many varieties of maidenhair ferns that make attractive houseplants. They are tolerant of low light, but not drying. If a maidenhair fern becomes too dry, the top will quickly die off. At that point it will have to be cut off. If the roots were not too badly damaged, new growth will again develop from the base. The maidenhair ferns used indoors are of tropical origin and not the same maidenhair fern we use outdoors in shady woodland settings.

Table ferns -- Pteris ferns -- are relatively small plants suitable for small pots or for use in combination planters or in terrariums. There are many varieties, but those with silvery venation appear to be the most popular. These ferns tend to spread through the pot and will need occasional division and re-potting to keep them growing vigorously.

Several different types of tree ferns are sometimes available for use indoors, but these are not as easily grown as many of the smaller ferns. They must be kept wet at all times because even a single drying can cause substantial damage; therefore, it is best to keep a small amount of water in a saucer beneath the pot. The tree fern, particularly the Australian tree fern, is one of the few ferns that tolerates very wet conditions. Do not allow other potted ferns to sit in water for any length of time.

Cool temperatures at night are the key to keeping most ferns in good condition indoors. High night temperatures often cause leaf yellowing and drop as well as speeding water absorption and lowering humidity. While the ferns that have been mentioned are the best types for indoor use, they still benefit from high humidity. Misting over plants or placing pots on gravel containing water for evaporation can be beneficial. This is particularly important if the cool temperature conditions mentioned are not possible. Where sufficient light is not available, artificial lights will help growth. Most ferns need at least 500 foot candles of light for 14 or more hours a day.

Touching fern foliage will not cause browning. But the small leaflets on the fronds are easily bruised; therefore, they should not be located where they are brushed by people passing by them.

Dr. Ray Rothenberger, Professor Emeritus, Department of Horticulture, University of Missouri