What is that Plant? A Close-up visit with Staghorn Ferns
March 21, 2022
By Karen Maxwell, Horticultural Specialist
Working in the gardens at Edison and Ford Winter Estates is truly a unique experience and fielding questions from guests about our extraordinary plant life is always a pleasure. Without a doubt, the most frequent inquiry is about our magnificent Staghorn Ferns found throughout the site. Perhaps you’ve seen them a hundred times and from a distance, they all seem to look alike, but let’s take a closer look at this exotic and curious plant.
Native to the rainforests of tropical Asia, Africa and Australia, our ferns are in the genus Platycerium, the name coming from the Greek for broad and horn of which we have two species: Platycerium bifurcatum, and Platycerium hillii, two species which thrive in our wet/dry environment, along with many cultivars (the result of purposeful or natural cross breeding). Ours are of the hardy species, meaning they can survive very brief periods of cold, down to 35 degrees or so. Of the 17 or 18 known species, collectors and scientists are hard pressed to positively identify all of the of cultivars or hybrids (hybrid or cultivar means the new plant will produce genetically matching offspring) and some may just be sports (genetic mutations that exist today). Despite the numerous variants in appearances, all Platycerium share common features: the same reproductive strategy, two kinds of fronds, a communal growth pattern, and basic environmental needs, though the size and width of fronds and direction of growth may vary greatly between species. P. bifurcatum, native to Australia and New Guinea is the most-commonly grown species and is the species or at least a parent of most of the Staghorn Ferns on our property.
As we see them suspended from chains and hanging on heavy tree limbs throughout the Estates, it is easy to forget their origins. Platycerium are ferns native to humid tropical rainforests and like orchids and bromeliads, they are considered epiphytes, meaning in the wild they live a soil-less existence, growing on the branches of trees, often in the canopy of forests, but in no way is one considered parasitic to the other. As a true fern, they neither produce fruit or flowers.
Staghorn Ferns are also called Elkhorn Ferns (particularly those with narrow fronds) or Moosehead Ferns due to the forked or antler like appearance of the fronds. Like all ferns, they naturally reproduce by spores. The pups can be removed once they are at least six inches wide and either planted or mounted on their own.
Alternatively, we may propagate them by division which is much quicker. In this method, a sharp knife is used to cut away sections that will then be mounted to a board, using sphagnum moss as a backing and securely tying the new section to the board that may later be attached to a chain and tree. The new Staghorn will grow right over its new mount.
When viewing one of our massive ferns (older ones may grow to weigh about 300 pounds), one is actually looking at a colony of individual ferns working together as a community to provide resources to all the residents. It was reported in Scientific Naturalist in May 2021 by researchers Burns, Hutton and Shephard that the Staghorn Fern is unique in the world of plants in that within a collection of ferns that appear as one, there is actually a division of labor – specific tasks performed by different ferns to insure the health and survival of the colony, much the way bees work.
Platycerium are made up of two distinct fronds: the basal or shield frond and the longer strap frond. Basal or shield fronds grow in individual halves and appear as one piece when mature, and they remain green while they are growing. The purpose of the shield or basal frond is to collect and hold moisture and nutrients. The shape of the shield frond, particularly its top edge, is a useful key in species identification along with how the particular shield frond attaches itself to the mother plant.
As they age, their color turns to a shade of soft cinnamon. In P. bifurcatum, the shield frond grows tight against the old growth, while the French Silver Staghorn Fern (P. veitchii), another species that will grow well in South Florida (though not as hardy as P. bifurcatum) has a top edge of the shield that is deeply and irregularly lobed. In the research conducted by Burns, Hutton & Shephard, they realized that the shield fronds actually soak up more moisture and water than the strap fronds or leaves that protrude from the collective.
At the base of each shield frond, there is a bud, which will produce the strap fronds (also called fertile fronds). These are recognized by their short stem and forking, which gives these plants their common name. Four out of every 10 strap fronds cannot reproduce and the remaining, or fertile fronds will produce spores that give the feel of velvet on the underside of the fronds. This velvet pattern is known as the sporangia and where it occurs on the frond is another key to identification of Platycerium species P. Hillii.
With the onset of warmer weather, the sporangia will appear and get continuously darker until they burst and expel their spores during the summer months. After the spores are released, the fertile fronds will return to their full green appearance. Each new frond will last between two to three years before they are replaced by longer and larger fronds.
With strap fronds of P. bifurcatum, the protruding leaves grow upright when new and as they age, they will hang down. Bifurcatum means twice divided, and the narrow wedge-shaped fronds divide into two major forks, and ultimately two to eight final splits or fingers. As in the shape of the shield frond, the shape and direction of growth of the strap fronds are further keys to establishing species identification. In addition to producing the spores that will result in the reproduction of the staghorn fern, the strap fronds are often covered with a waxy or dust-like substance (which should never be wiped off). It was discovered that this fabric of very fine hairs, actually allows the strap fronds to direct water to the nest of shield fronds which may further distribute their collected water via the fine rhizomatous root system hidden behind the shield fronds to the rest of the plant colony.
All staghorn ferns will thrive in high humidity – ideally over 70 percent – and those fine hairs on the strap fronds easily absorb the ambient humidity. These plants can be easily grown as houseplants if grown with a nice loose and well-draining soil in a pot, while providing their preferred indirect light and high humidity (it’s possible they will only ever produce strap fronds). Staghorn ferns should never be grown in full sunlight. A filtered light or shady spot is ideal and giving each one its own space will provide the best setting to appreciate their beautiful growth patterns and individuality. If grown as a mounted specimen, it will take the plant six to seven years to produce fertile fronds, provided all of its natural requirements are met. Staghorns will get all the water they need if grown outdoors in South Florida. If we have an extended hot spell, (when temperatures remain above 80 degrees) without water, an occasional hose spray once a week will be appreciated. When it’s cooler, the staghorn doesn’t need much water.
Here at Edison Ford, our climate is quite suitable to P. bifurcatum, so no additional feeding is necessary as the plant derives all its needs from the rain, humidity and detritus that falls onto and breaks down on top of the colony. There is street lore that cutting up a banana peel and placing pieces under the shield fronds will feed the Staghorn. While it does offer a little potassium and phosphorous, that alone isn’t sufficient for a mature Staghorn fern as it also needs nitrogen to grow. If grown indoors, a balanced liquid fertilizer twice a year is all that is needed. Some growers caution against using banana peel, as commercial bananas are treated with a fungicide which may not be healthy for the Staghorn.
A mature P. bifurcatum can grow to four feet wide in approximately 20 years and outgrows many gardens in Southwest Florida. Because of this, Edison Ford has become the recipient of approximately 30 different Platyceriums, the majority being cultivars of the P. bifurcatum with shield fronds about 12 inches wide and strap fronds to three and a half feet long.
The French Silver Staghorn (P. veitchii), which can also be grown in Southwest Florida has narrow strap fronds, gets its common name from the fine matted hairs that protect the fronds from sun and give the two-foot fronds a whitish-gray appearance. It is considered semi-hardy to 40 degrees, so some cover during very cold periods should be provided. The other so-called hardy Staghorn fern in our gardens is P. hillii, generally considered a desert species; however, at Edison Ford, we have the cultivar Magnificent, which produces dark green strap fronds nearly two-feet wide and three-feet long with distinctive kidney shaped, 20-inch-wide shield fronds. The shortened fingers of the new fronds grow upright and since this desert species plant is actually thriving in our humid climate, perhaps it has some P. bifurcatum in its lineage.
The Dwarf Staghorn, (Cheiroglossa palmate, syn. Ophioglossum palmatum) is a rare and small Florida native fern, unrelated to the Staghorn fern, but it grows similarly. Discovered in 1875, growing abundantly in Sabal palms along the banks of the Caloosahatchee River, it is also known as the Hand Fern and is considered endangered due to over collecting and reduction of native, humid hammocks. Not only is it illegal to collect the Dwarf Staghorn, but it is also important to note that it’s impossible to transplant or cultivate the plant once it is removed or detached from its home in an old boot or leaf base of the Sabal Palm.
As new fronds for all Staghorn ferns take on many different shapes until they mature, it is important to purchase a rare variety from a reputable dealer or assume the plant is P. bifurcatum as it is the most common and easiest grown Staghorn in Southwest Florida. They grow so easily that the Florida Exotic Pest Plant Council has it listed as a category # invasive species.
Generally free from pest problems, the inside of the mature colony is dead but as it naturally grows on a strong tree, the mature staghorn can return the favor and serve as the host to other plants. Thanks to Mother Nature, the birds and other means of plants finding new homes, some of our Staghorns at Edison are homes to
orchids, air plants, and in one case, a young Royal Palm has taken up residence.
Upon your next visit to Edison Ford, take a closer look at any two Staghorn Ferns and see if you can spot the differences.
*Indicates plants in the Edison and Ford Winter Estates gardens.