Getting to Know Ferns

by Catherine Kavassalis

Ferns are extraordinary plants. From deserts to the Arctic, ferns grow around the globe, with some 12,000 species in 45 families. They share a truly ancient lineage tracing back more than 400 million years. 

Ferns mixed with Solomon Seal in the display garden at Lost Horizons.

Fern artwork from the New York Public Library Digital Collection

Newly emerging Ostrich ferns, Matteuccia struthiopteris

Dryopteris filis-mas 'Crispa Cristata'

Ferns and other shade lovers in the display garden at Lost Horizons.

Over that expanse of time, great diversity has evolved. From the minuscule pond plants to towering trees, ferns come in a huge range of shapes and sizes. While most ferns are terrestrial, some live on rock cliffs, others on trees and still others underwater. 

Some may live for decades underground, like the Adder’s tongue Ophioglossum reticulatum. That outstanding fern has the highest chromosome count of any known living organism – up to 1,260 chromosomes (compare that to 46 in people). 

With such extraordinary variety, the fascinating lives of ferns are worth getting to know.

The underside of a Japanese Beech Fern, Phegopteris decursive-pinnata.

The underside of a Barnes Narrow Male Fern, Dryopteris filix-mas 'Barnesii'.

The feathery fern that comes to mind when we picture a fern belongs to the plant in its spore-producing phase. This sporophyte is only half the story. 

Unlike most plants, ferns can live two quite distinct lives. A fern in the sporophyte phase can reproduce vegetatively (clones) or it can release spores. Unlike seeds, spores have just one set of chromosomes. 

These haploid spores can still transform into small plants. But these plantlets, called gametophytes, look nothing like their parents. They are small, easily overlooked, and often resemble little green hearts. 

Though a few ferns will stay in this phase indefinitely (like the Weft Fern - Trichomanes intricatum in Ohio), most will grow sex organs that produce ova (eggs) and sperm.  Those flagellated sperms need the right conditions to swim to an egg on a different gametophyte. Only once an egg is fertilized can a new sporophyte develop. It is really quite remarkable.

If I had to choose one fern to grow, it would be a Royal fern (Osmundaceae). Why? Fossils of royal ferns dating back over 200 million years show that these ferns have changed little over time and were underfoot while dinosaurs trotted about the land. 

How cool to grow a Cinnamon fern (Osmundastrum cinnamomeum) and watch little ruby-throated hummingbirds collect the downy wool (indument) to line their nests knowing that Jurassic birds may once have flown above this same fern. Alas, I have trouble growing Cinnamon fern in my dry sandy yard. Like most ferns native to North American woodlands, it prefers moist soil in shade or part shade. 

I am able to grow its beautiful cousin, Royal fern, Osmunda regalis in a manufactured bog (pond liner underground) with the prehistoric-looking Equisetum hymenales. This horsetail fern is easy to grow in any water-holding container and makes a very attractive display on decks in full sun or tucked into perennial borders. 

Consider adding aquatic four leaf clover ferns (Marsilea sp.) or one of the lovely aquatics like Salvinia molesta or Azolla filiculoides. BUT KEEP THESE AWAY FROM WATERWAYS, AS THEY ARE HIGHLY INVASIVE!!!

A Selection of Ferns for Average to Dry Soils 

It should be noted that the division of ferns into two lists, one with recommendations for ferns for average to dry soils and another for ferns for moist conditions (in part 2), is somewhat arbitrary. There are many other conditions at play (soil texture and drainage, soil/rock/substrate temperature, slope, air flow, light intensity, etc.), so please bear that in mind.

Maidenhair Spleenwort Fern, Asplenium trichomanes 

Native Range: Six distinct taxa around the globe
Height: 20-30 cm (8-12 inches)
Spread: 20-30 cm (8-12 inches)
Light & Exposure: Part-shade to shade–Xeric 
Zone: 3-9
This dainty evergreen fern has striking black stems and round pinnules. It forms irregular clumps. Great for rock gardens. It is a variable fern with six subspecies; some thrive in acidic soils (ssp. trichomanes) others alkaline (ssp. quadrivalens). Incredibly tough once established.

Lady Fern Athyrium filix-femina (Northeast)

Native Range: North America, Asia 
Height: 30-100 cm (1-3 feet)
Spread: 30-75 cm (1-1.25 feet)
Light & Exposure: Part-shade to shade (tolerates part-sun with watering) 
Zone: 4-8
This is an easy-care classic fern from with finely divided light green fronds growing in attractive clumps. Recommended cultivars include: ‘Encourage,' 'Victoriae,' and ssp. cyclosorum.

Japanese Painted Ferns, Athyrium niponicum 

Native Range: Asia 
Height: 20-45 cm (1-1.5 feet)
Spread: 30-60 cm (1-2 feet)
Light & Exposure: Part-shade to shade (tolerates part-sun with watering) 
Zone: 3-8
Known for its pastel coloured gray-green fronds with reddish midribs, this deciduous fern with arching fronds should grace every shade garden. Recommended cultivars include: ‘Pictum,’ and ‘Pewter Lace,’ ‘Silver Falls.’

Hybrid Lady Fern ‘Branford’ (Hybrid A. filix-femina x A. niponicum)

Height: 30-60 cm (1-2 feet)
Spread: 30-60 cm (1-2 feet)
Light & Exposure: Part-shade to shade (drought tolerant) 
Zone: 4-8 
‘Branford’ was the “best looking” fern in late August after severe drought in the Chicago Botanic Garden trials (2015). It forms verdant mounds with wine colored stems and makes an attractive groundcover. ‘Ghost’ is a slower growing hybrid cultivar with silvery foliage, but it is not as drought tolerant as ‘Branford.’

This post was written by Catherine Kavassalis

About Catherine:

Catherine Kavassalis is a passionate gardener and conservationist. A scientist, educator and inspirational speaker, Catherine endeavours to stimulate interest and awe in the living world. She is member of the Halton Master Gardener group, the Past President of Oakville Horticultural Society and a former member of the Board of Directors for the Royal Botanical Gardens. Catherine loves to garden and has had her own eclectic organic garden featured on several tours.

For more on cultural conditions of ferns, visit the authoritative Hardy Fern Foundation hardyferns.org