How to Grow Ferns
Having selected the most suitable position for the fern beds, and this usually is the worst position for the majority of flowering plants, the ground should be well prepared by digging over, about a foot deep, breaking up theand mixing in a liberal dressing of leafmould, or fibrous peat, and some extra-coarse grit. This is particularly important if the original soil is at all heavy, especially if it is very dense clay.
The incorporation of compost, half-rotted beech or oak leaves, spent hops, fibrous peat, or spent mushroom compost, whenever any of these is available, helps to break up a clay soil. Any type of humus-forming material is valuable; those mentioned are regarded as the better ones. The broad-leaved horse chestnut, plane trees and the like do not make such good leafmould but it is better than nothing.
If there is room in the garden, the stacking of dead leaves in autumn, to rot down for subsequent incorporation with the soil, is an important chore. The following spring the half-rotted material is very useful indeed in improving soil texture and fertility; it warms a cold soil and helps the soil organisms to do their work in releasing food material from the clay.
Spent hops sometimes are readily available if there is a local brewery; usually it is necessary to make arrangements to collect as soon as the material is turned out. It will need stacking for a few weeks before using.
Local councils may be approached in the autumn for supplies of dead leaves. Where there is street planting of trees it is usual for the leaves to be collected as soon as they fall, by special conveyances, and while there may be a few odd cigarette cartons mixed in, and a good deal of road grit, it is a valuable source of humus where there is space to store it until half rotted. Usually it can be had for the asking or for a moderate charge. The road grit is useful in itself.
When you make such a stack, half the work is done if there is a corner between two walls. The leaves can be stacked up to four feet or thereabouts, retained in position with wire netting and stakes, and the top leaves prevented from blowing about by throwing on a few shovelfuls of soil. The heaps should not be trodden down hard, but allowed to settle under their own weight.
The addition to the fern bed of coarse sand, well-weathered ashes, crushed brick or stone, also helps to break up heavy soils and provides a congenial medium for fern roots; they love to wander among small stones interlaced with humus-forming materials.
Very fine peat is not recommended; it tends to cause caking of the surface and subsequent cracking in dry weather.
Animal manure is not suitable unless it is so old that it has become mould. It encourages soft growth which in turn encourages attack by pests, and renders the fern crowns more susceptible to frost damage in winter. The aim is to provide a light spongy rooting medium which will retain moisture but at the same time allow excess moisture to drain away readily.
The above recommendations may sound as though a lot of work is entailed in getting ready for growing a collection of ferns; but if the garden is in good heart and already cultivated, so much may not be necessary. But the neglected corners which are especially recommended often have not been cultivated at all, and then such preliminary work really is very well worth while and will repay the cultivator many times through the flourishing condition of his plants.
If the chosen position is under trees, probably the ground will be full of roots, and is likely to get very dry in summer. In that case careful exploration of the ground usually will reveal areas where holes can be excavated between the roots, to be filled up with compost, and the ferns may be planted in these selected areas where they can get established and able to compete with the tree roots. The latter will invade these pockets quickly enough, but not before the ferns have got a good hold and are able to cope, even if an occasional soaking is necessary.
In such a position a biennial mulching, once in spring before growth starts, and again in autumn at leaf fall, will be invaluable in keeping the plants in good health and steady growth. In any case an annual mulching with an inch or so of well-rotted leafmould is of great assistance to the ferns which form their new roots near the surface. Such a mulching is also a good method of keeping down annual weeds.
If baled peat is being used, it should he well soaked before using, as it may take several weeks to absorb moisture from the soil when it is dug in dry, and in the meantime may do more harm than good to plants placed on top of it. Generally I break up the peat in a watertight barrow, filling this up to the top with water and turning the peat until it is uniformly dark with moisture.
Before planting, a dressing of bonemeal, four ounces to the square yard, forked into the top six inches, is of great assistance in getting the ferns off to a good start; the gentle action of bonemeal releases food material slowly over a long period, and this is so much better than using more quickly available fertilizers, which indeed may be harmful.
Planting can be done at any time between March and early October, during moist rainy weather. The time when growth is starting in spring, and in September when the ground holds enough warmth to stimulate free root action, are the best times. Mid-winter should be avoided if at all possible.
When ferns are ordered from a nursery, they may arrive at a time that is not convenient for planting. In any case they should be unpacked, and if the roots are at all dry they should be soaked for a few minutes in cold water. If they can be planted immediately, so much the better, but if not they should be stood upright in boxes of wet peat, the crowns only exposed. Or they may be heeled in, ie. placed upright, almost touching, in shallow trenches of soil which is drawn up to the crowns, completely covering the roots. The important thing is to prevent the roots getting dry. A thoroughly dry fern is a dead fern nine times out of ten. I have received ferns imported from America, sent without soil, and tied up in a polythene bag, so dry that all life had gone before they reached me.
When planting, enough room should be left between plants to allow for their full development, according to the requirements of each variety. Such species as the Male Fern, Dryopteris filix-mas, and most of the Dryopteris family and their varieties, will need at least a square yard per plant, excepting the dwarf forms, and Dryopteris villarii, for which a square foot would be enough. The Polystichums, or Shield Ferns, also need ample room, and in the case of the varieties with more or less horizontal fronds such as Polystichums setiferum divisilobum, allowance should be made for them to spread out as much as five feet, in congenial surroundings, and if large mature plants are being planted.
Young pot-grown or recently lined out-plants will not need so much room to begin with, and it may take three or four years for these to reach their final size. In this case it is more important to furnish the ground and they may be planted, say, one to the square foot, and separated later as they develop.
The Lady Ferns, Athyrium filix-femina, vary a good deal according to variety; a three-foot square for strong growers, a two foot-square for medium growers and a one-foot square for the dwarfer forms will be adequate. Most of the varieties of Hartstongue will need about a square foot. Ferns with creeping underground rhizomes such as the Oak and Beech Ferns should have their slender roots spread out just below the soil surface, and should have enough room to wander about reasonably; a square foot to a plant would be enough to begin with.
If acquired as pot-grown plants, such ferns should have the root ball gently shaken out without injuring the roots and the growing points situated just below ground-level, and made firm.
In the case of ferns which form crowns, the rootstocks usually are covered with hard woody frond bases between which the young roots have to make their way. Frequently the oldest part of the rootstock is moribund and this should be cut away until clean live tissue appears. Then, starting from the bottom, snap off or cut away the old frond bases, being careful to avoid cutting away good roots, removing all the old bases nearly but not quite up to the new fronds; then plant with the crown flush with the soil surface — not below — spreading out the roots horizontally and making firm.
The removal of these old frond bases helps the plants to root quickly into the new soil, and is particularly important with the Polystichums, where the dense accumulation of old bases can prevent the new roots reaching the soil before the crown dries out.
Of course, in the case of young or recently propagated plants this procedure is not necessary.