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The term "Pteridophyte"
refers to vascular plants with independent gametophytes and motile sperm
that are usually classified into 4 divisions that comprise nearly 40 families.
They include over 9,000 living species (ca. 365 genera) distributed worldwide,
with 893 species (124 genera, 76 hybrids and 176 infraspecific taxa) in
North America north of Mexico (Kartesz, 1994).
![]() 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." |
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As a fern develops, the young stipe or stem of the frond is quite interesting and unusual as it unfurls. It is sometimes called crosier since it resembles a shepherd's crook or a bishop's staff. | This is an established holly fern. It grows best in warmer areas but often survives in protected locations in colder parts | Spores dropped from the fronds of an established fern have developed prothallium on the gravel surface. Each prothallium produces male and female organs (sexual or gametophyte stage). When fertilization of the female gametophyte occurs, small plants then begin to develop as shown. |
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Leatherleaf ferns don't like normal household temperatures. They grow best in temperatures under 75°F. |
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. Humidity 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. Light 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.
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This asparagus fern needs dividing or transplanting to a larger pot. The root system has exerted enough pressure to crack the pot. For best results, don't wait this long to divide or transplant ferns. |
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. Dividing Ferns 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. Watering 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. Grooming |
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Sprengeri fern, along with the true ferns, needs grooming periodically to remove dead stems and dropped leaves. | This "curly" fern is a selection of Boston that does not grow as large, but is noted for its lacy appearance. Note the fronds that have reverted back to Boston. These should be pruned out to maintain the curly look. |
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Scale insects are the most serious pest of ferns. The Boston fern illustrates unthriftness and shedding of leaflets (pinnae). Infested plants yellow, shed leaflets and gradually die. | A close-up of leaflets (pinnae) and stem (stipe) shows the clustering of the scale insect. |
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. Terminology The following terminology is used by fern specialists, botanical and/or fern societies:
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