Chapter 6. Hardy Ferns For The Rock Garden

Ferns can always be distinguished from other plants by two characteristics. First, their young fronds are curled up tightly and gradually unroll as they grow, till the whole leaf is flat and visible. Secondly, they bear, generally on the back of their fronds, lines or masses of very small pods that look like fine brown powder. These pods contain the "spores" from which the young ferns grow. Each genus of fern bears these pods in a different manner: some laterally across the leaf; others longitudinally up the frond; and some in masses. There are, again, numerous species in each genus, all with slightly different traits.

The great variety found among ferns, both as regards size, appearance, and the conditions under which they flourish, makes them one of the most useful of plants to the gardener. They are found all over the world, and vary in size from the tiny moss-like specimens found on walls and in rock crevices to the gigantic tree ferns of the New World.

There used to be an idea that ferns would only do really well in a warm temperature, but this has been found untrue even of many of the exotic kinds. Of course, our own hardy ferns provide a wonderful variety of beautiful kinds, but there are many foreigners which will succeed equally well out of doors in our climate. Ferns may be grown among other plants in the rock garden; they can be planted in masses in some cool and shaded spot in the marsh garden; or some place may be devoted to them alone, and most charming fern gardens may be made in parts of the garden where nothing else flourishes, for most of the hardy kinds of ferns will do well with practically no direct sunlight.

Habits And Requirements

To ensure success with hardy ferns a study must be made of the habits of the plants when growing in their natural home. The British ferns can be seen and observed, but there are many species of hardy ferns which come to us from North America; others are natives of Japan. These last named are fairly hardy, but will sometimes die during a very hard winter, if no protection is provided. The hardy ferns, as a general rule, like a sheltered and shady position where their roots can get plenty of water. They must have ample air and light, however, or they will become drawn up and weakly. Where they grow naturally, they are accustomed to a certain amount of protection from frost, for this is provided by their own dead fronds, and sometimes by the fallen leaves of trees and bushes growing near them. When grown in the garden, therefore, the dead leaves should not be cut away in autumn, but should be allowed to remain until after the frosts of the following spring. In their natural habitat ferns also receive a good supply of water during the winter months whilst they are dormant. These conditions should, therefore, be imitated as closely as may be in the garden.

The soil in which the ferns grow should not be sodden with water in the winter, but if planted where they do not receive the natural rainfall, they should always be provided with a sufficient supply to keep the roots cool and fresh, and to encourage them to form good strong growths when they begin to sprout in the spring.

Ferns like a good, deep, loamy soil, with ample leaf-mould, peat, and some coarse sand in it, and although kept moist, it should be well-drained, for ferns cannot bear a water-logged soil. They are especially intolerant of heavy clay. A compost of one part of fibrous loam together with one part of leaf-mould, peat, and sand will be found suitable to most ferns. There are just a few which will flourish only in boggy and marshy places, but even these prefer their water supply to be in the form of a running stream or from the occasional overflowing of a pool. Among these water-loving ferns is the well-known and popular Osmunda regalis, the Royal Fern, which may be found on warm and sheltered stream-banks and under wet cliffs in the southern counties. The ferns which grow in the cracks of walls and in the crevices among rocks, and therefore apparently exist in dry conditions, do not do so in reality. Their fibrous and spreading roots penetrate the cracks in all directions and find coolness and supplies of water in the hottest weather. Ferns grown on a wall or in the rock garden do the same thing, so that it is not sufficient to give them rocks to creep amongst; they must also be able to find good soil and an ample supply of moisture under and among them. In planting ferns together, a good deal of care should be expended in their arrangement, and the evergreen and the deciduous kinds should be evenly distributed so that no one particular patch of soil shall be bare and uninteresting throughout the year.

Some Native Species

The Athyriums are fine native hardy ferns, deciduous, and therefore only seen in leaf in summer, but well worth growing. The best varieties of the Athyriums are all hardy, but sometimes require a little protection to the young fronds in spring. The Hart's-tongue fern, Scolopendrium vulgare, is a very well-known native kind, and looks very beautiful lining a hollow bank or ditch with its long, shining, strap-shaped fronds. It has a great many varieties, all of which are evergreen and succeed best under cultivation on steep banks in the shade, and in a light, loamy soil of a calcareous nature. A native kind, S. v. crispum, is a pretty variety, with broad, undulating fronds with a crinkled and fringed edge. Some of these ferns, such as S. v. Kelwayii, form little bulbils on the margins of the fronds, which may be carefully removed and treated as seedlings, when they will soon make strong young plants. They like a sheltered site in moist, sandy loam and leaf-mould to which has been added a little mortar-rubble.

The Hard Fern Blechnum Spicant is another good British hardy fern, being evergreen with pinnate or divided fronds. It enjoys shade, and grows naturally in deep hollows and dells where the soil consists chiefly of leaf-mould and dead leaves, with a good loam beneath. The polypody, Polypodium, is well known in its wild state, many of its numerous varieties growing freely on old tree stumps and roots. Of its varieties, P. vulgare cambricum is one of the prettiest and at the same time one of the oldest. These ferns do well in rock gardens, liking fibrous loam, peat, leaf-mould, and a little sand as a mixture in which to grow. They may be propagated by division, and this is the best way if it is required to keep the strain true to its characteristics. It is evergreen and, unlike many ferns, bears sunlight well. It does not prefer it, however, and flourishes best in partial shade.

The Oak Fern is related to the foregoing, being really a Dryopteris. It is a very pretty fern, of a beautiful pale green colour, and is deciduous. It likes a very sheltered position, where its pretty three-partate fronds flourish well. The Beech Fern, another Polypodium, viz., P. Phegopteris, is like the Oak Fern, but differs slightly from it in the arrangement of its fronds. It likes plenty of moisture when dormant, otherwise its treatment is the same as Oak Fern.

The Shield Fern, Polystichum, has several varieties, of which the Soft-shield fern, P. angulare, is the best for general use. These ferns are evergreen and many of the varieties in cultivation are crested and plumose. They like a sheltered position, but do fairly well anywhere, their chief demand being for a rich loamy, well-manured soil. P. aculeatum is much like P. angulare, except that it has a more shining surface. Its habits are quite similar.

Another polystichum P. Lonchitis is known as the Holly Fern, and grows in high places. It is, as its name implies, a prickly fern, and is of a rather delicate nature, calling for care in the matter of watering. If it is allowed to get too moist when dormant, or if it is planted in too warm a spot, the plant is likely to die.

The Nephrodium (syn. Dryopteris) Filix-mas, the Male Fern, and N. var. pseudo-mas are both good species. The first is, perhaps, the best known of all British ferns, and does well in town conditions, growing in great clumps in suburban gardens. It is deciduous, but owing to its habit of keeping its fronds very late in the autumn and shooting out very early in the spring, it is very nearly as useful as some of the evergreens. It will grow practically everywhere, shade suiting it, perhaps, better than full sunlight, but it is quite happy in partial sun.

When planting these ferns they should be put in deeply, the crown being only just above the surface of the ground. N. pseudo-mas is an evergreen, with a few pretty crested forms.

Pteridium aquilinum is the common Bracken, too well known to need description. It likes a peaty, sandy soil, and is best raised from seed, or more correctly "spores," for the old roots, or rhizomes, are apt to do badly when replanted.

The Bladder Fern (Cystopteris bulbifera) is a pretty deciduous fern, doing well in many places where most plants would fail, though it is not good for culture in pots.

Imported Ferns

Among the hardy ferns introduced from North America the best for garden culture is, perhaps, Adiantum pedatum. This is a deciduous fern, and makes fine big clumps, if well grown. When the clump is in good condition and strong when planted, fronds as much as two feet high are often produced in the first season, increasing in size as the plant becomes established. It resembles Nephrodium Filix-mas in keeping its fronds very late and renewing them very early.

Polystichum acrostichoides and P. a. grandiceps are both good imported rockery ferns, and there are many others which do well. Most of these ferns like protection from the early morning sun, and should be looked to and perhaps protected during the late spring frosts. All hardy ferns do best in a situation in which they get the direct sunlight, if at all, only in the late afternoon.

The Propagation Of Ferns

Propagation by Spores. Ferns may be increased by several methods. The most usual method is by means of "spores" which are contained in small pods, generally found on the underside of the fronds. When these pods are ripe, that is just beginning to burst, the fronds should be picked and wrapped in smooth white paper. If these are undone after a day or so, the paper will be found to be covered with fine brown dust, which looks like brown pollen and is composed of millions of tiny "spores." Put some two inches of drainage crocks into the bottom of a clean pot, fill it up to within an inch of the top with a compost of equal parts of loam, peat, leaf-mould, and sand that has been passed through a quarter-inch sieve. Then press this down firmly, pour boiling water over it to sterilize the soil. Should there be any broken pots near, break them up until they will pass through a quarter inch riddle, then cover the soil in the pan or pot where the spores are to be sown, soak well, after which sow the spores in the broken crocks and cover with a sheet of glass and brown paper and stand in a shady moist corner. Every other day dry the steamed glass and replace.

In about two weeks' time a green film will be seen to have grown over the surface of the broken crocks; later this will assume the appearance of green scales, which after a little time will put forth tiny fronds that must be pricked off and be potted up singly when large enough. This is best done by using forceps to prick off each small piece of growth-covered crock.

The spores are sown in the same way as seeds (see Sowing Seed in the chapter on Propagation), but the compost used must first be sterilized with boiling water and then allowed to cool thoroughly. Ferns may be propagated by spores at any time of the year, but preferably in March or July.

Propagation by Division. This operation is best carried out in spring, that is to say, in March or April, at which time the ferns are planted out. (See Division of Roots.) The roots should be cut apart with a sharp knife, and the small plants can then be planted out in the positions they are to occupy permanently.

Propagation by Trailing Roots. This is the simplest of all the methods and is appropriate to such ferns as the Polypody. It consists in cutting off an inch or so of the tuberous root and potting it up. The root must, of course, have a frond sprouting from it.

Propagation by Minute Plants on the Fronds. On Shield Ferns and some others small replicas of the parent plant appear from time to time on the fronds. If it is desired to increase the ferns, the frond bearing these little plants should be cut off and pegged down on to light, sandy, well-sieved, and smooth soil.

The little plants will soon root, and as soon as this is accomplished they can be cut apart and potted-up. A close, moist atmosphere will encourage the rooting.

The following list, although of necessity far from complete, gives an adequate selection of beautiful genera, species, and varieties. Do not, therefore, as is so often the case, fill the fern garden with common species and neglect the more interesting, but equally hardy kinds. Remember, too, in planting, that the smaller-growing kinds must not be overcrowded by those of more vigorous growth.

Some Hardy Ferns

NOTE. For Fuller Cultural Details see Chapter 12, Alphabetical List of Plants for the Rock, Wall, Paved, and Marsh Gardens.

NOTE. Although most ferns can be raised from spores, the numerous varieties of some of the species are not likely to come true when so raised, and should, therefore, be increased by division.

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