As with garden ferns, the three major areas of concern when growing ferns indoors are soil, light, and water. In addition, attention to temperature is more critical and must be determined by the preferences of the individual species or cultivars.
Sacks of fern-specific soil, usually containing various combinations of peat, sterilized compost, and perhaps sand, pumice, and/or perlite, are easily purchased from most garden centers and are in general ready to use. I find many somewhat heavy, however, and prefer to cut them with a gritty amendment, so as to improve drainage. Well-washed pumice is always excellent, but perlite (which I find unaesthetic) and other inorganic additives may be used as well. Some growers amend with an orchid media.
As with outdoor containers, indoor containers require a drainage hole and the pot size should be just a bit larger than the plant's root ball. Most of the offerings need good but indirect light. East or north windows are usually the best, but south and west, when the light is tempered by gossamer curtains, work well. For most ferns direct sun is a killer. Air circulation keeps the fronds fresh. However, drafts, especially those from forced air heat or doors open to cold winter breezes, can be lethal, or at least damaging.
Watering is usually the biggest problem with indoor material. More house ferns die from drowning than from thirst. They should be well-watered, allowed to drain, and then watered again when the soil surface is dry. If the plant dries out quickly, it may be getting pot bound and ready for a new container approximately 1 in. (2.5 cm) larger in all of its dimensions.
Many ferns, such as adiantums (maidenhairs), have high humidity requirements, and these give indoor ferns a reputation as being temperamental. The easiest way to maintain them is in a cozy greenhouse. In the average home the most popular accommodation is to sit the pot on a tray of pebbles and water. Another option is to group plants in close proximity so that they offer humidity to each other. Do not mist them. Contrary to the recommendations of some authorities, I do not mist any indoor ferns as the moisture can remain on the foliage and eventually lead to mold and rot. This is especially a concern with maidenhairs or the dense ruffled Nephrolepis types where exposure to air is minimal and consequently evaporation takes place slowly.
Lacking the predators naturally present in outdoor gardens, indoor ferns will on occasion be visited by uninvited guests who help themselves to whatever edibles are to
their liking. Aphids, multiplying like rabbits, will suck the juices from the foliage and spread viruses, but can be washed away with a sink bath.
Other pests are either common or nonexistent depending on your locale. Beware of scale, however, which is universal and, once-present, difficult to bring under control. Small infestations can be treated by hand with dabbed applications of alcohol. If the entire plant is overrun with marching (and propagating) crowds, it should probably be discarded or at least quarantined and treated with chemicals. Chemical controls vary, however, and should be used with extreme caution. Oil-based sprays should never be used.
Periodic feeding of a very mild fertilizer at half the manufacturer's recommended strength should keep the plant happy. This is best applied when the fern is in active new growth, which brings me to the subject of grooming. Old fronds need to be removed and this can be a monster chore when the subject is naturally dense. With maidenhairs, I give them a complete haircut in the spring. They will be unsightly for a period, but the other option is to remove the fronds individually, a procedure for folks who have far more free time than I do.
Nephrolepis exaltata (the basic Boston fern) and its many cultivars, both for basket and table, are the easiest, most readily available and highly recommended for beginners or experts. I have a customer whose N. exaltata 'Bostoniensis' has been passed from generation to generation since 1935. It is an heirloom that is appropriately regarded
with passionate pride. Davallias and assorted "animal-footed" ferns are also easy, as well as forgiving, in bright light and occasional forgetfulness in the watering department. Pellaea rotundifolia (button fern) is one of my favorites, but unfortunately one of the first to succumb if over watered. The staghorns are popular and have a dedicated communal following, but require specialized conditions. (See the Platycerium entry for details.) Almost all of the ferns generally considered "indoor" types can be grown outdoors in California, Florida, and other warm climates.
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