Growing Ferns (B 737)Download PDF
- Facts About the Life Cycle
- Dividing Ferns
- Growing Medium (potted plants)
- Pest Problems
- Landscape Plantings
- Native Fern Species
- Fern Varieties
- Sources for Native Ferns
Ferns became popular indoor plants during the Victorian Era. Today, they are used as specimens in atriums, greenhouses and conservatories and we find them in the smallest apartments to the largest homes. They offer a quiet, graceful beauty by softening landscapes indoors and out.
Among the nonflowering plants, ferns and their relatives are unique. Numbering about 9,000, they represent a wide assortment of plant forms, and they have a very unusual life cycle.
The life cycle is unusual because it consists of two distinct generations of two different plants. The fern, as we know it, is the sexless or sporophyte generation.
Instead of growing from seed like most flowering plants, ferns come from a single spore that develops into the sporophyte. Spores are born in a spore case. The case contains many individual spores and is usually found on the underside of a leaf (frond) or on separate stalks. The photograph in Figure 1 shows spore cases on the underside of the leaves (pinnae) of a holly-leaf fern. Inexperienced gardeners often become concerned over these fruiting bodies and assume their plants are infested with unusual insects.
The reproduction of ferns from spores is different from other plants because there is an in-between stem (asexual stage). The individual spore is extremely small and germinates into a flat leaf-like body called a prothallium. The sexual stage comes next. Sexual organs develop on the underside of the prothallium, and fertilization occurs. Depending on the kind of fern, it may take two to six months after fertilization for the first fronds to appear.
Usually, gardeners and greenhouse producers don't reproduce indoor ferns from spores. Most indoor ferns are separated into several pieces by root division. Details for both are given under the sections "Dividing" and "Potting."
Even though most ferns used for indoor culture are native to the tropics or subtropics, they for the most part prefer a cool temperature and a high level of moisture in the air (humidity). In the woodlands or tropics, ferns are found under rather dense canopies of trees or large woody plants. Some species are native to rather dry climates that have periods of heavy rainfall. Usually these periods of rainfall occur during hot weather, thus providing a cooling effect.
Room temperatures that are comfortable for human beings are usually a bit warm for many ferns. Nighttime temperatures for ferns should be on the cool side, preferably below 60°F. Daytime temperatures should not be above 72° and preferably cooler.
When ferns are grown outdoors during summer, they should be located in the cooler areas of the garden, usually in deep shade or on the north side of the house or a garden structure. Never expose ferns to full sun in summer.
Growing ferns inside your home is a real challenge. Culture today is not as easy as it was in earlier years. The increased difficulty stems partly from the changes in our lifestyles. As we have become more affluent, fern culture has become more difficult. Before the widespread use of forced air or steam heat, there was usually a cool room where the humidity was a bit higher. Forced air and steam heat tend to dry the air and reduce the humidity below the point where ferns can survive. A humidity level of 30 percent is about as low as most ferns will tolerate. Forty to 50 percent is certainly a more desirable range.
There are several ways to overcome dry air. You can add humidifiers to your home heating system or buy a self-contained electric humidifier. A humidifier will produce not only better environmental conditions for your ferns and other house plants but also a healthier atmosphere for you and your family.
If you don't want to purchase a humidifier, put pots of ferns or other plants in saucers or trays filled with gravel and water. This increases humidity around the plant. Always maintain the water level just below the surface of the gravel so the bottom of the pot won't be standing in water. Some indoor gardeners add charcoal chips to the gravel. This helps keep the water clean and odor free. For best results, replace the gravel periodically or wash it thoroughly at three-month intervals or as algae, etc., start to develop in the water or on the gravel. Sanitation is important in keeping down diseases.
When you grow ferns in decorative tubs, ceramic or cache pots without drainage holes, put an inch of gravel in the bottom of the container. A better approach is to plant the fern in a clay pot and set inside the decorative container. Then put sphagnum moss in the space between the two containers. Keep the moss moist. This helps increase humidity and prevents rapid drying of the soil.
During winter when your heat is on, many ferns need misting. Use an atomizer, plant mister or a plastic spray bottle that gives off a fine mist. Mist the plants early in the morning. Apply enough to moisten the fronds. Ruffled or fluffy (finely textured with dense foliage) ferns are a bit sensitive to too much water on their foliage. Mist these types only when your air is extremely dry. Broader- and thicker-leaved ferns may need daily misting when your heat is on frequently or for long periods.
Humidity is one of the most limiting factors in fern culture. Without a fairly high level of air moisture, most ferns will be unattractive and unhealthy.
There is a fern suited to almost any condition found in the average home. For example, holly ferns (Cyrtomium falcatum) grow in low to medium light, while birds nest ferns (Asplenium nidus) grow in low to bright, but not direct, sun. A northern window usually provides ideal light conditions for many types of ferns. You can use a sheer curtain or drape to cut intensity. During summer months, you need to reduce light in eastern or western windows by about 50 percent. Asparagus ferns, which are not ferns but belong to the lily family, require bright light year-round and thrive in direct sunlight. Check the cultural chart for the specific light requirements of several different types of ferns.
Ideally, an attractive and healthy fern will have just enough room to accommodate the root system with about an inch of space for further growth. Most ferns develop shallow root systems, so shallow pots or pans are best. To maintain the proper balance of root systems and space, some ferns, depending on growth rate, need repotting several times a year.
When you pot, remember that a small fern in a large container looks rather ridiculous and will be more subject to problems because of moisture excesses, etc. Start small ferns in small pots. Shift them to the next size pots as they become crowded.
Inexperienced gardeners repot ferns just as the pots seem to be three-fourths full. However, you should wait until the plant seems to be spilling out of the pot before repotting. Remember that some ferns grow rapidly, while others are extremely slow. In time, you will learn the growth characteristics of the ferns you enjoy.
Years ago, clay pots, wooden boxes or moss baskets were the most popular fern containers. Today, however, many gardeners use plastic pots. Growing plants in plastic pots is a bit different than other containers because moisture and air cannot move through plastic. This means you have to water the plants less often.
Regardless of the pot you use, you will be more successful if the containers have drainage holes. In potting, place an inch of gravel or clean pieces of broken pots in the bottom of your container. This keeps the drainage holes from clogging. Also, make certain the pots are thoroughly clean. If you've used the pots for other plants, you should scrub them thoroughly with a strong detergent and hot water. It's also a good idea to soak the pots in a solution of one part household bleach and nine parts water. This eliminates disease problems. In mixing and handling the bleach solution, exercise caution. You may injure your skin and eyes if you handle the solution improperly. When using new clay pots, soak them in clean water overnight, preferably longer. This rinses away any chemicals and thoroughly moistens the pot. A periodic washing of the pots is desirable too. This helps remove scum, soil, accumulated fertilizer salts or other materials that might clog air spaces in clay pots.
Potting new plants is relatively simple. After you clean old pots or soak new ones, put gravel or broken crockery in the bottom. Then, partially fill the pot with your potting soil or mixture. Do not pack the soil. Pull the root ball apart so you can spread the roots outward to the edges of the pot. This space facilitates watering. Gently firm the soil if necessary but be careful not to cover the crown of the plant. Water thoroughly to moisten all the soil.
If you're repotting old or potbound plants, thoroughly water them to make them easier to remove. Do not try to pull the fern from the pot. Instead, put your fingers between the fronds at the base of the plant. Invert the pot, then tap the rim on a table or hard surface. The plant should come out easily after several firm taps. Shift it to the next pot or divide it.
Often times, ferns such as Boston and sword outgrow their pots; then you have to divide or discard them. When it comes to dividing, ferns can take rather harsh treatment. In some cases, you may have to use considerable force to remove the plant from the pot. Once it's free, use a sharp, long-bladed knife to halve or quarter the root ball. Then, pull each quarter or half apart so you can spread the roots in the new soil. The main requirements after dividing are to water the roots and new soil thoroughly and to provide a humid atmosphere by misting the first few weeks.
Growing mediums vary considerably for the many types of indoor ferns. However, all good mixtures have several things in common. They are well drained because of different components like coarse sand, gravel and charcoal. Most mixtures contain considerable organic matter like peat moss, peat humus, leaf mold, ground sphagnum moss and manure. A soil mixture for ferns must hold adequate but not excessive moisture, contain organic matter and be well aerated so air can move through the soil.
The proportion of the materials varies from one mixture to another depending on the fern. Some gardeners prefer rotted leaf mold. It is most like one of the main ingredients of the soils where many ferns naturally grow. Peat moss and ground or shredded sphagnum moss are more widely used because they are easy to obtain. Artificial mixes used by commercial plant growers are available to the gardening public now and are excellent for ferns.
Regardless of the mixture you use, be sure it is thoroughly mixed. Damp ingredients are easier to mix and pot. They are also safer for the plants.
A typical mixture contains equal parts of peat moss, sand and garden soil. Add lime (one teaspoon per quart of mixture) for the types of common ferns. Other ferns, like maidenhair, thrive in a mixture of one-half peat moss, one-fourth garden or potting soil, and one-fourth of a mixture of equal parts sand, charcoal chips and manure. Usually, for maidenhair, a tablespoon of ground limestone is added per gallon of mixture.
Other mixtures might have ingredients like manure and charcoal. Both are good additions to any mixture. Manure provides nutrition, and charcoal improves drainage. Check the cultural chart for specific mixtures for different types of ferns. If you use a mix with charcoal, you might try chips from aquarium supply stores.
Supplying moisture is very complex. This is due to variations in the needs of the plant, its size, the soil mixture and the environment (temperature and light) in which the plant grows. Ferns are certainly no exception. However, for a wide range of them, you can expect to water fairly heavily, particularly during the growing season. This may mean watering daily or once a week. There are no hard and fast rules. To know when to water ferns and all other plants, you must develop a sense of feel of the soil. This is the only way to determine when to water.
Some gardeners water by soaking ferns in clay pots in a sink or tub of water for a few minutes. If you do this, remove the plants as soon as they are soaked, usually when the bubbling stops. Don't submerge the plant when you soak it. Some ferns are sensitive to being covered with water, even for a few minutes. Also, fronds of some types are very brittle, while others are extremely soft. The weight of excess water may break or damage them.
Your watering practices determine your success with ferns. Over or under watering are by far the most common reasons for poor results. Shedding or leaflets occurs very rapidly if the plants are under or over watered.
Ferns need grooming periodically to help them maintain health and vigor. This simply means removing dead fronds or matings of dropped leaflets. This is particularly important in the fluffy types that may be quite compact. Keep the pot clean. Wash it occasionally with warm water and a soft brush.
Ferns have relatively few pest problems. However, when they do occur, they can be devastating. The major pests of ferns include fern scale, hemispherical scale and several species of mealy bugs.
Scales are usually hard-bodied insects without visible legs or means of movement. They may be white or brown, depending upon the insect. Mealy bugs are soft and appear to be covered with a white, mealy or downy substance. The presence of honeydew, a sticky syruplike material on the foliage, is an indication of fern scales or other insects. If the insects continue to excrete the honeydew, a black moldlike algae or fungus develops and gives the entire fern a blackened appearance.
When you purchase plants, inspect them carefully to make certain they are free of insects. Check the tops and bottoms of the leaflets and the stems. Do not buy any plants showing the slightest sign of insects.
For years, ferns were considered extremely sensitive to most common insecticides. Consequently, a general recommendation was to discard plants infested with insects. Research in recent years indicates that many ferns are tolerant to some of our insecticides with only slight injury resulting. However, few, if any, pesticides are cleared by governmental agencies for use on ferns.
The basics of growing ferns in the landscape are the same as growing them in pots. Site selection in terms of drainage and light exposure is critical to production of high-quality ferns. Ferns require well-drained soil. Sandy soils or humus soils with good surface drainage are preferred. Heavy clay soils or soils with a shallow clay pan should be avoided or amended to provide good aeration and drainage. Elevated beds with amended media are excellent sites in the landscape because they ensure good aeration under most conditions. Light intensity is another key factor in site selection for plantings of ferns. Ferns either prefer or require indirect light for production of high-quality fronds (leaves). They are excellent plants for shady areas where other plants will not grow well. Avoid direct exposure to afternoon sun. Outdoor planted ferns can be divided by separating clump or cutting off established runners. The best time for dividing outdoor ferns is after the first frost through November. This gives the transplants plenty of time to regenerate roots. No fertilizer is needed for fall transplants.
The following terminology is used by fern specialists, botanical and/or fern societies:
- Blade - main part of a frond; generally stipes plus blade make up the frond.
- Caudex - stem or stalk of the fern plant
- Fertile leaf - a leaf that bears spore cases or "fruit dots"
- Frond - the leaf of a fern
- Fruit band - on some ferns, a line of spore cases occurring on the leaf margin or underside of the leaf
- Leaflets - one of the divisions of a compound leaf
- Midvein - the central and most prominent vein of a pinnae
- Pinnae - leaflets that are arranged along the blade
- Rachis - a continuation of the stipe that extends from the base of the plant to its apex
- Rhizome - stems, above or below ground (usually below ground), producing fronds above and roots below
- Sori - spore cases on ferns
- Sorus - spore case of ferns
- Stipe - stem or stalk of a frond
Dunbar, L., 1989. Ferns of the Coastal Plain. University of South Carolina Press, Columbia, SC.
Foster, F. G., 1971. Ferns to Know and Grow. Hawthorne Books, Inc., NY.
Hoshizaki, B. J., 1975. Fern Growers Manual. Alfred A. Knopf, NY.
Jones, S. B., Jr. and L. E. Foote, 1990. Gardening With Native Wild Flowers. Timber Press, Portland, OR.
Lellinger, D. B., 1985. A Field Manual of the Ferns and Fern Allies of the United States and Canada. Smithsonian Institution Press, Washington, DC.
Mickel, J. T., 1979. How to Know the Ferns and Fern Allies. Wm. C. Brown Co., Dubuque, IO.
Phillips, H. R., 1985. Growing and Propagating Wild Flowers. University of North Carolina Press, Chapel Hill, NC.
Snyder, L. H., Jr., and J. G. Bruce, 1986. Field Guide to the Ferns and Other Pteridophytes of Georgia. University of Georgia Press, Athens, GA.
Birmingham Fern Society: Birmingham Botanical Gardens, 2612 Lane Park Road, Birmingham, AL 35223, (205) 879-1227.
Native Gardens: Route 1, Box 464, Greenback, TN 37742, (615) 856-3350.
Piccadilly Farm: 1971 Whippoorwill Road, Bishop, GA 30621, (706) 769-6516.
Sunlight Gardens: 174 Golden Lane, Andersonville, TN 37705, (423) 494-8237.
Meadowbrook Nursery: Route 5, Box 724, Marion, NC 28752-9338, (704) 738-8300.
Woodlanders, Inc.: 1128 Colleton Ave., Aiken, SC 29801, (803) 648-7522.
Grateful appreciation is expressed to Rodney Coleman for assistance in the preparation of this publication. Appreciation is also expressed to Callaway Gardens of Pine Mountain, Georgia, where many of the ferns were photographed.
Authors acknowledge assistance of Henry Clay and Jeff Lewis, horticulturists.