Beautiful Native Plants

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Wednesday, June 29, 2016

Ferns in the landscape

Ferns create a soft edge between a wooded area and a lawn. Here you see a mixture of netted chain ferns and cinnamon ferns along with magnolia, St. Johnswort, sweet gum, and more.

Ferns are Living Fossils

Ferns belong to the Pteridophyta Division of the plant kingdom in that they have leaves, roots and stems, but since they spread by spores, ferns do not have flowers, pollen, fruits, or seeds. Today's ferns descended from ancient plants that covered the earth long before the seed plants (the gymnosperms and angiosperms) made their appearance.

And even today with millions of insects and other bugs available in the ecosystems, the ferns carry on their life cycles without any animal involvement. (See below.) The gymnosperms, such as pines and other conifers, also don’t need animal pollinators because they are wind-pollinated, but gymnosperm seeds do serve as food for many wildlife species.

This cinnamon fern has been used by a bug as shelter.
It has neatly wrapped itself into the tips of the fronds.
This is not true for the angiosperms; by the beginning of the Cenozoic Era (65 million years ago), the first bees, wasps, butterflies, and moths are recorded as being present then. This means that there were plants with flowers that attracted these insects and other pollinators. These plants had the advantage of less wasted pollen compared to wind-pollinated plants. Eventually the varied shapes, colors, and odors of flowers allowed sensory recognition by pollinators and excluded unwanted, indiscriminate pollinators.

Certain plant and insect species have had a profound influence on one another’s evolution. It is also an advantage for the pollinator to have its own private food source.

Today, over 65% of angiosperms are insect-pollinated and 20% of insects, at least at some stage, depend solely on flowers for their food. But ferns seemed to have skipped this step and do not appear to serve insects or other wildlife in any specialized way.  Even so, I include many different ferns in my wildlife-friendly landscape because they do provide shelter.

Fern life cycle

Fern life cycle shows the alternating generations.
Credit: © Merriam-Webster Inc.
The fern life cycle has two stages: the gametophyte and the sporophyte. The one we notice is the sporophyte, so named because it produces spores—the dust-like, one-celled particles—by the millions. Spores are produced in sacs called sori (plural of sorus), located on fertile fronds that may or may not resemble sterile fronds, depending on the species. The unequal drying of the alternate thick and thin-walled cells that line the outer surface of the sori causes miniature explosions to disperse the spores. At that size scale, the expulsion of fern spores is said to be one of the more explosive events in nature.

When the wind-blown spores land on suitable places, such as moist soil or cracks in rocks, they germinate into small, heart-shaped gametophytes with male and female parts. Gametophytes are always small because they have no vascular parts and must absorb any moisture directly by osmosis. The male parts produce flagellated sperm that need moisture to move to the female gametophyte. A new sporophyte is the product of that fertilization.

Given this complex process, is it any wonder that many ferns spread asexually via well-developed rhizomes? Most ferns you purchase have been divided from cultivated fern stocks. Once they are established in your landscape, you may multiply your ferns by dividing them. It’s a mathematical oxymoron.

The fronds of the ferns are normally divided into leaflets. Singly pinnate fronds such as the Resurrection Ferns have one main stem with rows of leaflets on either side. A doubly pinnate frond means that the leaflets are divided again into sub-leaflets and so forth.

Netted chain fern makes a wonderful
ground cover in full or partial shade.

Using Ferns in the Landscape

I’ve always loved ferns in the landscape and on my porch. I have two Boston ferns that are clones of one that a neighbor gave me more than twenty years ago. They have been on my various porches all those years. That old neighbor has passed, but I think of her often when I admire her ferns.

I like ferns in the landscape, as well. To me, there is less pressure growing ferns rather than flowering plants where you are always waiting for the flowering season and where have to work at coordinating the flower colors and make sure that not everything blooms at once. With ferns there’s no pressure because you’re never waiting for flowers; it’s their graceful fronds that are appreciated. They work best in partial or fully shaded areas where you may have trouble getting other plants to flower.

I was pleased to find a number of different ferns already growing on our property when we moved to Florida in 2004. I’ve encouraged them along the edge between the lawn and a wooded area. As the ferns spread into the lawn, the lawns gets smaller–at a rate of 12 to 18 inches every other year as I make my rounds along those edges. The editing of those edges consists of pulling grass that is creeping into the ferns; pulling up tree seedlings that are too close to the lawn; pulling out some of the vines that have grown into the lawn or up trees I wish to preserve; pulling out the invasive tuberous sword ferns, and then laying in a good layer of arborists’ wood chips, which is tamped firmly into the soil next to the lawn. The goal is to make the mowing easier and to have a neat-looking edge.

I learned that two of the ferns growing here are Florida invasives. I think I’ve defeated the Japanese climbing fern (Lygodium japonicum) , but the tuberous sword fern (Nephrolepis cordifolia) is still a big problem in our yard.

Cinnamon ferns form stately bunches.

Fern Species in my Yard

The Cinnamon Fern (Osmundastrum cinnamomeum), a large fern growing to three or four feet under the right conditions, sports its cinnamon stick-type, spore-laden, fertile fronds in both the fall and the spring here. The fertile fronds wilt away after the spores are released leaving the green fronds for us to enjoy until frost when they die back for the winter. Here in Florida we enjoy a longer fern cycle and our cinnamon ferns produce fertile fronds in the spring as their sterile fronds emerge for the season and then again in the fall before they die back. This beauty can survive in nearly full sun to full shade, but it’s happiest in moist soil. I’d categorized this as a specimen or bunching fern, not a ground cover.

Royal ferns provide a lacy texture in the landscape.

Another large, specimen fern, the Royal Fern (Osmunda regalis), is truly regal in its size, growing to three to five feet—even larger than its close relative, the Cinnamon Fern. The Royal Fern’s doubly pinnate fronds have more widely spaced leaflets making it appear lacier.

The fertile sections of this fern appear at the top of the main fronds. After the spores are released the tops will fall off. The Royal Fern doesn’t seem to be as tolerant of full sun as the cinnamon ferns, but partial sun is fine and it does best with its feet wet. It dies back in the winter.

On the underside of the netted
chain fern’s fertile fronds:
the sori form a chain.
The Netted Chain Fern (Woodwardia areolata) is a wonderful groundcover forming dense, one-foot high mats in the forests. It grows in full shade to mostly sunny. Its fertile fronds start out like a regular leaf, but then curl inward, turn a rich, shiny brown, and grow taller than the sterile fronds. This is the most plentiful fern in our yard.

Its fronds are singly pinnate meaning that its leaflets are not again divided. This provides a less lacy and courser appearance than most other ferns. Its coarse texture provides a good contrast with other ferns. In planning a garden-space leave room for these ferns to spread. It dies back in the winter. These are the ferns that have worked so well along the edges of the lawn areas.

Bracken ferns have a triply pinnate triangular frond.
Bracken Ferns (Pteridium aquilinum) inhabit much drier locations than most other ferns, and one source stated that Brackens are the most abundant fern on a worldwide basis. Some of the Bracken clones in Europe are known to be hundreds of years old.

Farmers consider Brackens to be noxious weeds because they have aggressive rhizomes that sprout new plants from small pieces, resist fire and are toxic to grazing animals.

Bracken fronds are triply pinnate and are more triangular in shape than most ferns. “Pteridium” is a diminutive of “Pteris”, Greek for “fern”, and “aquilinum” is from the Latin for “eagle” and refers to the wing-like fronds of this fern.

Over the years, I’ve never successfully transplanted a bracken and I haven’t seen it for sale, but I was happy to see some growing in a wooded area in front of the house. It dies back in the winter.

This epiphytic fern looks dead most of the time,
but when it rains, it springs to life!
The Resurrection Fern (Pleopeltis michauxiana) is unlike the other ferns on my list, because this one is an epiphyte, which means it doesn’t require soil. In fact, these little ferns, growing only to four to six inches, seem to occur most frequently on the tops of the more horizontal branches of live oaks (Quercus virginiana). Most of their lives, they look dead, but as soon as there’s water they spring back to life, hence the common name. It stays brown through the winter whether it rains or not. I don’t have many on my property, but I do enjoy them wherever they appear.

You can't purchase this fern and it's not going to transplant well, so we enjoy where it plants itself.

The fertile frond of grapefern is attached  
 to the base of the triangular sterile frond.

The Rattlesnake Fern or Grapefern (Botrychium virginianum) is a winter fern that you might miss, because it’s only six inches tall. It dies back in the summer months. I’ve found it growing along the edge of the woods in several shady places.

I was especially happy to see it come up after I’d removed a thick invasion of invasive wedelia or creeping oxeye daisy (Sphagneticola trilobata).

I love it when a big invasive removal project has a lovely side benefit of allowing this native fern to come into its own.

The holly fern is easy to identify
because of its holly-shaped leaflets.

Holly fern (Cyrtomium falcatum) is an usual-looking fern with its singly pinnate fronds and with leaflets that look sorta like holly leaves. It’s evergreen and is widely sold all over the state. I was excited to find one growing under a magnolia tree that backs up to the wooded area out back. My excitement waned when I found out that it’s not a Florida native; it’s native to Japan. At this point I haven’t decided whether I will remove it from the edge of the woods to a container or just let it be to see what it does. I’m leaning toward a container to let the native ferns work things out amongst themselves.

The tubers in the roots are the “tell” for this
 Florida invasive species.
Tuberous Swordfern (Nephrolepis cordifolia)  is extremely invasive and I can attest that it’s difficult to eradicate. This is especially true when it’s covering large swaths of the neighbors’ properties. It’s not easy to distinguish this fern from the native Boston fern (N. exhaltata) until you pull it up. The tubers are the “tell” and I heard recently that they are edible. They’re supposed to taste like celery, but I can tell you that it’s not worth the effort to wash them unless you are starving. They are crunchy, but they don’t taste like much and have a weird musty aftertaste.

The fertile fronds of the cinnamon fern are produced twice a year in Florida.

So that’s my ferny story and I’m sticking to it.

© Ginny Stibolt