Green in Winter: Ferns

Polypody fern in winter.
Polypody fern in winter.

Last week I posted on ground cedar, a fern ally. This led me to think about true ferns which stay green in winter. At our farm we have two:  common polypody (Polypodium virginianum) and evergreen wood fern (Dryopteris intermedia). Snow now covers all the interesting native evergreen ground covers and that is a good thing. We had one night in the first week in January when it got down to less than – 30° C with only a few centimetres of snow, a potentially plant-killing combination. I love the idea of winter gardens and enjoy looking at the pictures of fine winter garden designs from Maryland or Oregon or even Niagara-on-the-Lake but almost none of it makes sense for the Ottawa valley. Even the majestic white pines are darkened to near-black ink drawings by -30°.

Still, the relatively open December meant we were out in the woods enjoying the muted colours and textures of the season and ground-hugging greenery, partially covered by fallen leaves, is part of the beauty of the early winter.

We do not have any Christmas fern (Polystichum acrostichoides) on the farm. I don’t know why; I must introduce some to a shady garden. The picture was taken at Shining Tree Woods, a nature reserve belonging to the North American Native Plant Society.

Christmas ferns.
Christmas ferns.

Because our rocks are granitic, for the most part, we do not have any of the lovely little evergreen ferns which grow on mossy limestone: walking fern and maidenhair spleenwort, among others. A quick trip to Asplenium in Wikepedia revealed a couple of surprises: there is a subspecies of maidenhair spleenwort which grows on acidic rocks, Asplenium trichomanes subsp. trichomanes, and ebony spleenwort (A. platyneuron) hybridizes with walking fern (A. rhizophyllum) – two very cool things to look out for on nature hikes.

Maidenhair spleenwort on mossy limestone.
Maidenhair spleenwort on mossy limestone.

On the south edge of the farm we have a ridge of the Quyon marble, a very, very old calcareous rock. At the base of the marble seam we have interesting shallow caves where porcupines overwinter. This is also the site of the greatest concentration of plants such as blue cohosh, bellwort and maidenhair fern, which like the relative richness of the soil. So far I haven’t found any calciphile ferns clinging to the marble cliff face. The little cliff-face ferns should be enjoyed when and where you find them; they are exceedingly difficult to propagate and cultivate.

Quyon marble on the south edge of the farm.
Quyon marble on the south edge of the farm.

The evergreen ferns of the forest floor are relatively easy to grow from spores. In years gone by, I have successfully raised little sporelings of wood fern and Christmas fern. Northern maidenhair is also easy to grow from spores. (The difficulty with maidenhair in city gardens comes when you set them out in the garden – they are devoured  by slugs.) I haven’t got any terrariums filled with fern sporelings on window ledges this winter, but it is something well worth doing. Perhaps I will try Christmas fern spores next winter – it would be the easiest way to get a lot of little Christmas ferns.

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Trish Murphy

Artist: botanical, still life, and natural history illustration. Garden designer: native plants and naturalistic gardens

2 thoughts on “Green in Winter: Ferns”

  1. Very interesting post. Nice that you have both acidic and alkaline soils. Here it’s all alkaline. I think now and then of planting northern maidenhair. Fortunately, slugs are not a problem in my garden.

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    1. Thanks! We don’t have much alkaline but there is a definite difference by the marble seam. My Toronto garden had a lot of slugs and snails. Here we have lots of slug-eating fireflies. And lots of maidenhair fern. It’s a great fern for a city garden.

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