Boston Ferns and Kidneys
(Editor's Note: This article was originally published on August 11, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Their names. Boston ferns, those ubiquitous plants in hanging baskets or on plant stands are known botanically as Nephrolepsis (nef-roh-LEP-siss) exaltata (eks-all-TAY-tuh). Nephro comes from the Greek word nephros meaning kidney. Lepsis is also Greek and means scale. The word refers to the kidney-shaped, scale-like structure of the indusia or spore cases (see photo below) which form a protective cover on the underside of leaflets for the reproductive spores. Exaltata comes from Latin and means very tall, not a characteristic that I would necessarily ascribe to this one-foot-tall fern, given the existence of tree ferns, which can reach heights upwards of six feet.
Nephrolepsis exaltata ferns are native to many humid tropical and subtropical regions of the world, including Africa, Central America, Florida, Mexico, Polynesia, and the West Indies. If that's so, then why the name Boston? This U.S. city is in hardiness zone 6, a long way from subtropical zones 9 and 10 in Florida! The mother plant of modern day Boston ferns and their cultivars (distinctive variations or mutations) was actually found in a shipment of tropical ferns to Boston way back in 1894. Thus it was named after the city in which it was discovered. It was grown commercially for the first time in 1914 in the state of Florida and subsequently became a popular parlor plant.
Depending on the source consulted, Boston ferns are said to be either easy to grow or hard to grow. They do need high humidity to look their best. Misting them frequently helps considerably, since they otherwise have a tendency to drop the individual leaflets on a frond prematurely. The leaflets of aging fronds will drop eventually, even in humid environments. Removing dead and dying fronds is a part of the necessary culture in growing this plant.
In addition to high humidity, these ferns grow best in light of medium intensity. Protect them from strong sunshine. Keep the soil evenly moist and use a weak liquid fertilizer every 2 weeks while plants are actively growing. Do not fertilize during the winter. Ideal temperatures range between 55 and 85 degrees F, but they will tolerate 50 - 95 F.
Be careful not to confuse the brown growths on the bottom of the fronds with scale insects. These are the kidney-shaped reproductive structures I mentioned at the beginning of this article. Scale insects will be distributed randomly on the fronds while the fern's spore cases are lined up in rows on the underside of the leaflets. Other insects that can infest the plants include spider mites and mealy bugs.
There are over 50 cultivars of Nephrolepsis exaltata. Among them is my favorite, called ‘Fluffy Ruffles.' (See initial photo above.) This is a really great-looking houseplant, smaller and fuller than the Boston cultivar. Its shorter 12-inch fronds extend outward and curl upward with overlapping ruffled leaflets, creating the fluffy appearance for which it's named. As old fronds die, new ones have already grown to cover them up. The dead fronds are normally not visible and form sort of a crinoline underskirt that gives the plant a fuller appearance. The brown fronds may be trimmed off, if you like, without harming the plant, but it will give the fern a much slimmer look.
'Fluffy Ruffles' is sterile and all propagation is by stolons (runners) or division of the clump instead of by spores. There's no problem here distinguishing between scaly aphids and spore cases, since the latter do not exist on this cultivar. It also is not as fussy about humidity and watering. It's even somewhat drought tolerant and doesn't fret much if you occasionally forget to water it. If my Fluffy Ruffles plant is any indication, it's also a very long-lived fern. I've had mine now for 31 years and have only repotted it twice! It has survived low humidity in the winter, a trip to Iowa from Alabama in a U-Haul trailer in July, and in recent years the annual transition from the relatively low light in our indoor tropical garden to the higher light levels outdoors during the growing season.
If you're looking for an unusual and beautiful house plant that can tolerate occasional abuse, this plant is the one for you. And it has a side benefit as well: It actually filters contaminants from the air in your home, including formaldehyde.
The only fly in the ointment is that it's somewhat hard to find. Since it's sterile and doesn't produce spores, mass propagation is limited to division of a clump or by runners that form from time to time, as I mentioned earlier. Perhaps with the advent of tissue culture propagation, this great fern will become more readily available. At this point, internet mail order sources are practically nonexistent. The only one I could find is www.paulasherbsandplants.com. However, Fluffy Ruffles is available from regional retailers through a wholesale grower. Wholesalers who grow Fluffy Ruffles include Tropical Gardens I, Inc., located in Mosinee, Wisconsin. Happy growing!© Larry Rettig 2008
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