I just love ferns. I'm sure it's a childhood thing, if not something primordial, then at least back to the womb. I have an early memory of getting lost in the bracken ferns. It was a forest with a canopy of fronds and green-gold light with a sky of fern-print patterns. I wandered in a trance until I could no longer hear a human voice. Eventually some life-saving inner voice whispered, "You ... are ... lost!" I cried out in panic, and heard my mother's voice. But that quiet, green fern world was worth it.
The patterns and variety of ferns still loses me. I don't understand the need for color and flowers in a garden, although I enjoy them, of course. Much of my youth was in Oregon and in the forest, so it was a love nourished. The delicate maiden-hair ferns clung dangerously to a waterfall cliff, anchored by moss, bouncing gently, and jeweled with water droplets.
We moved to south Florida from San Francisco (where lush gardens of ferns live in Golden Gate Park, including 15-foot Australian tree ferns: an adult "bracken forest") in 2005. One of the great surprises was south Florida's fern mecca. Broward has nearly 40 fern and fern-like native species and some are abundant. (Photo of frond and in the wild by George D. Gann)
One of those is the "Wild Boston Fern" (Nephrolepis exaltata) that has graced the parlors of America, not only in Boston since the late 19th century, but coast to coast. It thrives indoors with a regular water and window-light. It's a graceful weeping potted plant with fronds 2½ feet or longer and foliage 3 feet in diameter. Hang it; put it on a pedestal or small table, or put it on the floor atop a reversed pot so the fronds can arch.
When you mistreat it by lack of water or direct sunshine, the fronds die, shouting out, "Water!" or "Stop the burning sunshine, please, only bright light!" When you resume watering regularly, it comes back. In south Florida indoor air-conditioning dries the air, so keep the moist. A small effort toward the humidity it prefers (open-window, spray mist, or away from the AC vent blast) will let it thrive indoors. It is hearty.
Extending your outdoor garden indoors is wonderful design and ideal for the "Florida room". Outdoors, the Wild Boston fern is a gift to the native gardener. It works beautifully as a ground cover 1-2 feet high in partial or even full shade. Too much sun and too little soil moisture will make it look straggly, so choose something else for an unirrigated xeric landscape. The moisture requirement is not high, so in partial shade almost any extra moisture (run-off, swale, downspout, A/C drip, humus soil, hand irrigation between infrequent rainstorms, etc.) will keep it full, healthy, and lush as a ground cover.
Pots of Wild Boston fern can grace stairs, porches, patios, walkways, walls, and ledges. Use a pot saucer, glazed pot, or plastic pot to reduce watering frequency, and keep the soil medium moist for a lush-looking plant.
You can hang Wild Boston fern or get even more creative remembering that it is also an epiphyte. You see it often in the boots of the Sabal Palm, but it will take to other natural and unnatural locations where some moisture is maintained for the roots. You could use it for a vertical garden, or tuck it into coral wall niches on the shaded north side.
So what's the "torture"? The torture is that the very similar-looking "Boston Fern" Nephrolepis cordifolia, also know as the Tubrous Sword Fern, is a Category 1 Florida Invasive plant that "invades and disrupts native plant communities". So we can't recommend "Boston Fern" without alerting the public to the imposter. We must help eradicate the use of Asian Sword Fern and tell nurseries to stop selling it. To do this we must be able to tell them apart. I made the mistake or bought wrongly-labeled plants before I understood the difference. It's difficult to eradicate Nephrolepis cordifolia, from your yard, but I'm working on it.
IDENTIFY THE CATEGORY 1 INVASIVE ASIAN SWORD FERN WITH CERTAINTY
So that you can enjoy the native Nephrolepis exaltata, native Wild Boston Fern
The Only Reliable Test: If it has tubers, it's the invasive N. cordifolia. Not every plant you pull from the ground has a tuber, but most do, so dig up a small patch looking for the firm, brown, greenish or yellowish grape-like tubers. It is the easy and only sure way for an amateur to know you have the invasive.
Okey, I'm going out on a limb here and bucking the advice of many experienced botanists who have written elaborately on this subject (e.g., University of Florida). They claim that the invasive N. cordifolia has dark scale attachments (see George Gann's photo of stems below) on the upper side of the petiole, that is, the stem below the leaflets or pinnae. Others say contrasting color between the scale and scale-attachment. They also claim the leaflets of invasive N. cordifolia overlap on the underside, mid-frond, covering the rachis (frond stem half way between the bottom leaflets and the tip). They claim the pinnae and frond are more blunt on the invasive N. cordifolia. They say the sori (actually the indusia or tissue covering the spore packets on the underside of the pinnae or leaflets) are "kidney shaped" (less closed) than the indusia of N. exaltata with horseshoe-shaped or more fully closed circles.
And I say, well maybe! But I spent many hours with a 30X binocular scope, and with reading glasses, looking at dozens of Sword Fern fronds and remained uncertain. The variety is wide and it seemed to me that no one standard works well most the time, and that even trends and tendencies are not easy to see. I think I understand this being out-of-sync-with experienced botanists phenomenon. Read on.
My first job was in a greenhouse in Oregon two blocks from my home. One of their specialties was fuchsias. They propagated about 36 varieties. After two years there, I was able to identify all 36 varieties by the leaf alone, before they were mature enough to bloom. I may not have been able to describe exactly how one looked different from another similar variety, but I knew. It comes from experience.
I think you, and even I, can probably learn to see the difference between a native N. exaltata, and N. cordifolia without digging them up, but it is tricky and subtle. Dig enough of them, looking for tubers, and you may learn to distinguish between them. In your yard it's easy to replant those hearty native Nephrolepis exaltata without tubers, so dig. My advice is to dig for tubers until you can guess correctly every time.
Yes, there are also many cultivars (highly-bred varieties) of N. exaltata, but most of those look big and fancy, unlike the wild Boston Fern in the Sabal boots and in the hammocks. Buy from a native nursery who shares your love of native plants, and always pull the pot off to check the roots for "bad tubers". That way you can enjoy one of south Florida's great botanical gifts, Nephrolepis exaltata, the Wild Boston Fern indoors and outdoors.