Everything you need to know about ferns, including drought-tolerant varieties

There is something otherworldly about ferns. Their fronds suggest feathers and wings, and so when looking at them you may think of taking flight, most likely into the pre-historic past when they dominated the landscape before flowering plants bedecked the earth. Ferns are classified as pteridophytes; the root meaning of “fern” is feather, while the root meaning of “pteridophyte” is winged plant.

Ferns reproduce by spores, which are mistakenly compared to seeds. Spores are found on the undersides of fronds in receptacles known as sori.  Sori are easy to identity as they are typically brown, bumpy structures arranged in symmetrical rows.  When sori open, spores are ejected onto the soil below. However, the spore of a fern does not germinate into another fern but rather into a gametophyte. The sprouted gametophyte is typically microscopic, heart-shaped, and contains both male and female reproductive structures. When the gametophyte reaches maturity, a sperm from the male structure swims through water on the soil surface and fertilizes an egg in the female structure. An embryo develops from the fertilized egg and will eventually mature to the point where a tiny leaf emerges from the gametophyte, which then disintegrates.

It is noteworthy that the gametophyte that sprouts from a fern spore and is responsible for fern reproduction has never been seen in a majority of fern species and, in the case of all ferns, spores are produced exclusively on the bottom side of fronds. For this reason, ferns – as well as fungi, mosses, lichens and algae — are referred to as cryptogams (crypto = hidden, gamos = marriage) since their reproductive apparatus is not readily revealed.

We tend to think of ferns as having a moist habitat and therefore as being water needy. Their feathery look might also create a first impression that they are delicate plants. But this is not the case. Many ferns have leathery leaves that impart a measure of drought tolerance. Most ferns have rhizomes which, like bulbs, may persist underground indefinitely, even when fronds have died from extreme weather conditions. Rhizomes actually serve the same function as stems (and bulbs, for that matter): Leaves (or fronds, in the case of ferns) sprout from their upper surface, roots grow from below, they conduct water and minerals, and they store excess carbohydrate as starch.

At least three California native ferns are known for a significant degree of drought tolerance, albeit in shady exposures, once established. The first is giant chain fern (Woodwardia fimbriata). It is called “giant” since it is the largest fern in North America, with fronds reaching up to eight feet in height in redwood forests up north, although they only get half that tall in a typical garden. It is called “chain” since its soris are arranged in neat and evenly spaced in even rows. Western chain fern (Polystichum munitum) is more drought tolerant than giant chain fern and may reach a height of five feet under cultivated conditions.

Deer fern (Blechnum spicant) does not have the stature of the above ferns, growing up to two feet only. Yet it more than makes up for its lack of size with unusual charm. Deer fern, contrary to what its name might suggest, is not eaten by deer. It produces both fertile (spore-bearing) and sterile fronds. The sterile fronds have an incomparably clean and delicate look, growing into a symmetrical mound. The fertile fronds emerge from the mound with thin, etheral fronds that offer a pleasing contrast to the thick foliage of the mound. At the close of winter, cut back old fronds before new growth begins. This fern is adaptable to a wide range of soil conditions.

You may also think of ferns as invariably green but would be mistaken. At the UCLA Botanic Garden there is an autumn fern (Dryopteris erythrosora ‘Brilliance’) whose new fronds are magenta pink, orange, and yellow. The irony here is that these fronds come in the spring, but since their coloration is suggestive of autumn, that’s the season designated in the plant’s name. You can have a fern garden consisting of the above four species virtually anywhere in California, as they are hardy down to 10 degrees below zero if not colder. Brake fern (Pteris cretica) has a variegated cultivar with large silvery leaf centers surrounded by green margins.

One of the most fascinating sights at the Huntington Gardens in San Marino is a gigantic staghorn fern growing on the trunk of a California live oak (Quercus agrifolia), an arboreal specimen that must be several hundred years old at least. Native to the tropics, staghorn ferns (Platycerium bifurcatum) can be adapted to most Los Angeles gardens, as they will survive a mild freeze. These ferns are called staghorns because of their deeply lobed, antler-shaped fronds. They are epiphytes or tree dwellers and, with some baling wire, may be attached to almost any tree trunk in your garden. Just make sure they get plenty of shade, regular misting and liquid fertilizer.

Another epiphyte of note is bird’s nest fern (Asplenium nidus), which typically is grown as a potted plant. It is one of only a few ferns with whole, uncut leaves and makes a dramatic statement in an entryway with its shiny, pale green fronds that can grow to 4 feet in length. The mother fern (Asplenium bulbiferum), like its bird’s nest cousin, has memorable coloration – yellow-green, black veined fronds – and personality. It produces baby ferns, called bulbils, on its fronds that easily can be detached and grown into new plants.

There are two commonly grown water ferns: Marsilea and Azolla. Marsilea grows on the edge of water ponds and looks like the perfect four-leaf clover.

Azolla, a minute plant that spreads out like a mat, makes its own nitrogen through symbiosis with microscopic algae. Azolla turns red on and off during the year. Its growth is dense and it can take over a water garden. Before it gets out of control, scoop up the excess and spread it over your garden as nitrogen-rich mulch.

Tree ferns are distinctive. A tree fern trunk is a collection of vertical rhizomes which must be kept moist for the tree fern to flourish. Growing to a height of 50 feet in their Australian habitat, they do not reach more than 15 or 20 feet in Los Angeles. The Tasmanian tree fern (Dicksonia antaractica) is hardy enough to survive snowstorms in its native land.

Holly leaf fern (Cyrtomium falcatum) exhibits dense, shrub-like growth to a height and width of three feet. It tolerates more exposure to both direct sun and winter cold than most ferns. Lady fern (Athyrium filix- feminia) grows nearly as tall, spreads out as a ground cover but is more sensitive to the elements. Another spreading fern, of smaller stature but greater durability, is leather fern (Rumohra adiantiformis).

“The Complete Book of Ferns” (Cool Springs Press, 2020), by Mobee Weinstein, is the only book on ferns you need to have in your library. It offers detailed information on how to grow and propagate ferns, including raising ferns from spores. Planting projects are featured, such as creating a vertical fern garden, a saucer terrarium, a dish garden, and a tabletop garden. Art projects with ferns are detailed, including making fern prints on linen napkins.

Tip of the Week: If you wish to propagate a staghorn fern, make sure it has matured to the point where it has produced several offsets or pups. You will want to separate the pup, identified by a shield that grows flush against the tree (or board, if it is mounted), at the base of the mother plant. Fronds will be growing out of the shield, under which rhizomes are to be found. Make sure the shield is brown before separation.Remove the entire pup by cutting underneath it with a sharp knife or machete or, alternatively, cut through it down through the rhizomes if you wish to create multiple new plants.

Find a board, at least one-half inch thick and one foot across, made of a hardwood such as oak or walnut. You can paint the board or cover it with water sealant. Make a circle in the board by hammering in a dozen nails so that the circle’s diameter is slightly larger than the diameter of your pup.

The day prior to surgery, water your staghorn well. At the same time, soak sphagnum peat moss in water and, the next day, wring it out prior to placing a clump of it in the circle of nails on your board.

Place the pup you remove from your staghorn in the center of the sphagnum and secure it with clear fishing line. Tie the line to one nail and secure it around another nail on the opposite side of the pup. Loop the line back and forth until the pup is securely fastened. Alternatively, you could place your pup in a wire basket lined with sphagnum moss.

Hang your staghorn under a tree or attach it to the tree’s trunk so that it receives morning sun or dappled light throughout the day. Soak it well every two weeks, or more often in hot weather, and make sure that the sphagnum moss does not dry out. As it increases in size, your staghorn’s tolerance of hot and dry weather will increase.

Please send questions, comments, and photos to joshua@perfectplants.com