Ferns in the Rock Garden and Rock Walls

Ferns in the Rock Garden and Rock Walls

Many of the smaller ferns find ideal conditions in rock gardens, dry stone walls, or in very stony ground; in fact, one wonders how some of the Spleenworts managed before man came along and built his old mortared walls. For Asplenium trichomanes, A. ruta-muraria, and the Rustyback, Ceterach officinarum, thrive in the old weathered lime mortar to such an extent that for every plant found growing in strictly natural conditions, in rock clefts and the like, hundreds are to be found luxuriating in the crevices of old walls.

This is especially noticeable in the case of the Ceterach. This charming little fern is very seldom found growing in purely natural habitats; in fact, I can recall finding ten or twelve only during the many years I have recorded fern distributions in locations which could be said to be free from man’s activities. Often I have found this fern growing in old quarry rubble, even on the flat amongst the gritty gravelly soil in old quarries, though normally it grows on more or less vertical faces. But far more frequently it is to be found in old walls, sometimes by the hundred.

fern growing in rock wall To a lesser degree the Brittle Bladder Fern, Cystopteris fragilis, colonizes similar places. The Hartstongue, too, often sows itself into the minute crevices in the mortar.

The Common Polypody, Polypodium vulgare, is also found far more frequently adorning the tops and sides of stone dikes and old walls than in any other position; there are many walls in Lakeland along the roadsides where the flourishing Polypodies extend for hundreds of yards with hardly a break.

The Black-stemmed Spleenwort, Asplenium adiantum nigrum, is another typical denizen of such positions, especially in dry walls built up with soil, as in the Devonshire lanes. I remember seeing a high retaining wall, near Uig in Skye, built with large stones, apparently without soil or mortar, where practically every crevice had the fronds of this fern extending from roots far back in the wall.

This preference for such habitats gives a very strong hint as to the best means of making these ferns happy in the garden, and it is true hat the closer we adapt our planting places to approximate to those where the ferns naturally grow, the more likely are we to succeed with them.

Usually one associates rock and wall gardens with shields and curtains of colourful alpine and rock plants, masses of colour from alyssum, aubrieta, helianthemums, phlox and many other free-flowering subjects, but to my mind the rock garden planting scheme is not complete without some foil of foliage, some cool verdure on which to rest the eyes, dazzled by the cushions of vivid colour.

The all-colour garden which so many people desire has a parallel in the world of music. Someone on the radio recently stated that more money is expended on brass bands than all other forms of art put together, yet the finest music is that of the full orchestra, where the uninhibited blare of the brass is modified by the tenderness of the strings and flutes, the bland and mellow notes of the woodwind.

I remember some years ago putting up a moderate-sized group of ferns at a Garden Show, and this was surrounded by large tiers of dahlias, chrysanthemums and other floral displays dazzling to behold. I was struck by the frequent comments made by visitors who appreciated the island of coolness set amidst the literally stunning impact of massed colour; one man was so good as to describe my effort as an oasis in a desert of colour beating down like the African sun.

Be that as it may, all colours gain by suitable contrast, as every artist knows, and in the garden the most restful contrasts are given by the many shades of green.

When buying weathered limestone for the rock garden one often receives as a kind of bonus a few plants of Spleenwort, usually A. rutamuraria, established in the rock crevices, and these should be cherished, as they are more likely to thrive than plants collected and introduced artificially.

All the Spleenworts are suitable ferns for the rock garden and they all are best established in vertical crevices filled behind with a mixture of leafmould, pounded old lime mortar rubble and a little loam, the crowns being wedged in position with small stones among the mixture. Firm planting is essential, so that the ferns can grow and bind the soil with their fine roots before it can wash away and leave the ferns with their roots exposed.


09. May 2011 by Dave Pinkney
Categories: Alpines, Ferns, Plants & Trees, Rockery Garden | Tags: , , | Comments Off on Ferns in the Rock Garden and Rock Walls


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