Adiantum capillus-veneris
Southern Maidenhair Fern

Adiantum capillus-veneris

I’m not sure why gardeners are so attracted to maidenhair ferns, but odds are the romantic common name which aptly describes the dainty foliage has something to do with it.  Plants from the fern genus, Adiantum have been cultivated for hundreds of years… first as a medicinal diuretic, tumor treatment, and hair tonic, and later as an ornamental house plant and hardy garden perennial.  I grew up with northern maidenhair fern, Adiantum pedatum, in my west Raleigh neighborhood, but it wasn’t until some 30 years later, when the late NC Botanical Garden curator, Rob Gardener, shared a piece of Southern maidenhair fern, Adiantum capillus-veneris, that I was hopelessly smitten.

As it turned out, the Southern maidenhair fern, Adiantum capillus-veneris, is endangered in North Carolina, and Rob’s plant had come from a very small population at NC’s coastal Lake Waccamaw. As I would soon observe, the North Carolina plant is quite different from the Adiantum capillus-veneris which is commonly sold in the trade, and is a marginally winter hardy, poor-growing dud. In a side by side comparison, the NC specimen is amazingly superior both in garden vigor and winter hardiness. I was curious…how could two different plants of the same species perform so differently? My quest for answers had begun.   
Soon I discovered our rare NC native fern is much more common outside our geopolitical boundaries. In fact, southern maidenhair fern is native in 25 of the 50 US states, even as far away as California. In horticulture, there are few things rarer than the same plant species being native to both North Carolina and California. 
The oddest of these native occurrences is a population of Southern maidenhair fern just below South Dakota’s Mt. Rushmore, which I had the pleasure of visiting several years ago. There, it grows in a natural hot spring, which allows it to endure the cold South Dakota winters. This offers no explanation, however, for the multiple populations discovered in the mountains of Southern Colorado…far away from the warmth that it seems to require elsewhere.  Did I mention that Adiantum capillus-veneris likes water, and virtually everywhere it’s found, you’ll also find water nearby, whether it grows along a stream or near a rock seep…often on limestone.  

Several years ago, I spent my Christmas holiday vacation at Arizona’s Desert Botanical Garden herbarium (plant mortuary) looking through their regional collection of deceased specimens of Adiantum capillus-veneris. The diversity was amazing from typical 8” tall plants from southern Arizona, to plants nearly 2’ tall from the Grand Canyon. Now, if I can only find time to return when the ground isn’t frozen, as has been the case during my two previous Arizona forays, to find Southern maidenhair fern.  
In subsequent travels, I found southern maidenhair fern growing wild in Northern Mexican streams, along South African rivers, on the side of buildings in Bermuda, and even in seeps in the dry Mediterranean climate of Crete. Other plant explorers have added to my collection with their accessions from China and France. We also now grow plants from 8 of the 25 states where Southern maidenhair fern is native and still on my radar are finding it in South America, Canada, the Middle East, and much of Asia. Only Australia and New Zealand seem devoid of natural populations of our NC native maidenhair fern.  
In the garden, southern maidenhair is hard not to love. The seemingly fragile, thin, glossy black, upright stems are adorned with the soft green leaves on multiple-branched fronds that just beg to be stroked. The delicate appearance, however, belies its garden toughness. A small start of southern maidenhair fern will lead to a 3’ wide patch in 10 years…especially if you keep the soil moisture average and add plenty of good compost to the bed when planting.  There’s also no need to worry about providing alkaline soil as long as your soil pH is somewhere between 5.5 and 6.5.
Although fully deciduous most years when the temperature drops below 15 degrees F, Adiantum capillus-veneris holds its foliage through most of January, so there are only a few months you won’t enjoy the dainty-looking, but deer-resistant foliage.  I hope you’ll add southern maidenhair fern to your plant love list, whether it’s the tender crested leaf forms which are only suitable as a houseplant, or the myriad of other great forms that add an amazing texture to the outdoor woodland garden.

– Tony Avent

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