FERNS FOR GARDEN AND GREENHOUSE
Ferns possess a beauty quite distinct from that of other types of plants, for it lies in the delicate gracefulness of their leaves or fronds, and their refreshing greenness. They are distinguished from flowering plants by their sexual method of reproduction. Instead of producing seeds, they form spores on the backs of the fronds or, in some cases, on special spore-bearing structures. The spores, when sown on damp soil, produce green, flat, heart-shaped structures about half an inch in diameter. These are the prothallia, and they produce the sexual organs, the female structure of which, when fertilized, gives rise to young Fern plants of typical appearance.
The different kinds of Ferns are classified principally by the structure and arrangement of the spore-bearing parts. Ferns vary in size from tiny mosslike growths, to the massive Tree Ferns with stout trunks 80 or more feet in height. Most have finely divided fronds, but a few, of which the Bird's-Nest Fern, Asplenium Nidus, is an example, have simple, undivided fronds.
As Ferns grow wild in all parts of the world, there are hardy, cool greenhouse and tropical kinds in so far as their cultivation is concerned. Altogether, something in the neighborhood of 10,000 species of Ferns have been identified, and many of them have produced numerous variants.
Hardy Ferns. The majority of these require a cool, shady position and moist soil; equal parts of loam and leaf mold suit most kinds. In sheltered positions hardy Ferns are best planted in autumn, but in exposed places planting should be delayed until spring. The soil must be kept moist by watering during the summer. The fronds of the leaf-losing kinds should not be removed until spring, as they provide protection for the young fronds. The dwarf hardy Ferns make excellent pot plants for a cool greenhouse or sunroom; they must be kept moist and shaded in summer.
Greenhouse Ferns. The cool greenhouse group includes those Ferns which require a minimum winter temperature of 45 degrees. They need shade from bright sunshine in summer, and the atmosphere must be kept moist at all times by frequently damping the floor and benches on which the pots stand. Tropical Ferns require the same treatment as the cool greenhouse kinds, but a minimum winter temperature of 55-60 degrees must be maintained.
It is very important never to allow the roots of most Ferns to become dry, for once their leaves wilt from this cause they seldom recover completely.
How to Pot Ferns. Repotting is done in spring or as soon as the fronds commence to uncurl. The times vary for different kinds, but generally the tropical Ferns are repotted in February and the cool greenhouse Ferns in March. Ferns in the house should be potted in March—April. They require a compost of equal parts loam, leaf mold and peat with sand added freely. Those which have filled their pots with roots are repotted in slightly larger pots. If the roots have decayed, all the old soil should be washed from the roots and the plants set in fresh compost, using pots just large enough to hold them. Generally, however, it is best to disturb the roots as little as possible, and on no account must they be overpotted.
Propagation by Division. Most Ferns can be increased by dividing the clumps. This is done when growth commences in spring. The rhizomes are cut through with a sharp knife and the divided portions set in separate pots, just large enough to hold the roots. A few, e.g., Asplenium bulbiferum, are propagated by removing the leafy buds found on the fronds. They are placed an inch apart, in pans of compost, and, later on, are potted in separate pots.
How Fern Spores Are Sown. Most Ferns are propagated by spores sown during spring or summer. The spores, when ripe, are yellowish brown or dark brown. A portion of frond is placed in a paper bag and hung in a dry place for a few hours to allow the ripe spores to fall to the bottom of the bag. These are sprinkled thinly on the surface of a finely sifted compost of equal parts of loam and crushed brick, in small pans half-filled with crocks. Before sowing the spores it is good policy to sterilize compost, crocks and pans, by baking. Panes of glass are laid over the pots, which are set in saucers of water. The pots of spores are placed in a greenhouse of the required temperature, and shaded with paper.
The prothallia, which develop from the spores are pricked out in small clusters at half an inch
propagated by spores sown during spring or summer. The spores, when ripe, are yellowish brown or dark brown. A portion of frond is placed in a paper bag and hung in a dry place for a few hours to allow the ripe spores to fall to the bottom of the bag. These are sprinkled thinly on the surface of a finely sifted compost of equal parts of loam and crushed brick, in small pans half-filled with crocks. Before sowing the spores it is good policy to sterilize compost, crocks and pans, by baking. Panes of glass are laid over the pots, which are set in saucers of water. The pots of spores are placed in a greenhouse of the required temperature, and shaded with paper.
The prothallia, which develop from the spores are pricked out in small clusters at half an inch
apart, in pans of sifted compost, when they are visible as very small plants, merely pressing them into the surface of the compost. They must be kept moist by standing them in water, and not by overhead watering until they have developed their first small fronds. When sufficiently large they are potted separately in 3-in pots, and subsequently in larger ones.
Ferns are not cross-fertilized by hand pollination as are flowering plants. The spores of two or more kinds are mixed and sown together and hybridization takes place naturally in the prothallia stage. The male element from the prothallia of one kind swims in the film of moisture and enters the female structure on the prothallia of another kind of fern, and fertilization takes place.
The Principal Kinds
Acrostichum. A large group of tropical and cool greenhouse Ferns, which vary a great deal; the spore-bearing parts are spread over the whole of the undersurface of the fronds.
Adiantum. A large group of hardy, cool greenhouse and tropical Ferns. These popular Maidenhair Ferns are distinguished by black shining leaf-stems and fan-shaped pinnules (leaflets). A. cuneatum, of which there are many varieties, is the most popular greenhouse kind, and A. pedatum, which grows to 3 ft. in height, is suitable for planting out of doors.
Alsophila. Tree Ferns from tropical America and Australia, with treelike trunks up to 8 ft. high, and terminal clusters of spreading fronds.
Angiopteris. Tropical Ferns, with large, spreading, evergreen fronds up to 6 ft. in length.
Asplenium. A very extensive genus, from tropical, semitropical and temperate countries. They differ greatly in the size and shape of the fronds—some are finely divided, others are entire (undivided).
Blechnum. Mostly tropical and cool greenhouse Tree Ferns with stems up to 4 ft. in height and large, feathery fronds. B. spicant is hardy.
Botrychium. Hardy Ferns, each with a single feathery frond and a spore-bearing frond. Height 6-8 in.
Cheilanthes. Cool greenhouse and hardy Ferns, which grow up to 12 in. in height; the finely divided fronds are covered with fine powder.
Cyathea. Tree Ferns from tropical and subtropical countries, having trunks from 2-40 ft. high and terminal rosettes of fronds.
Cyrtomium. Cool greenhouse Ferns with evergreen, pinnate fronds up to 21/2 ft. long.
Cystopteris. Dwarf hardy Ferns with elegant deciduous fronds.
Davallia. An extensive genus of chiefly tropical Ferns; most have very ornamental fronds and creeping rhizomes covered with brown hairs.
Dicksonia. Evergreen tropical and cool greenhouse Tree Ferns, with stout stems up to 40 ft. in height and large, feathery fronds.
Doodia. Cool greenhouse Ferns growing 18 in. in height and having pinnate fronds, some of which are tinged with rose.
Dryopteris. An extensive genus of Ferns from tropical, semi-tropical and temperate countries. They form large rosettes of feathery fronds up to 4 ft. in length.
Lygodium. Hardy, cool greenhouse, and tropical Ferns, with twining stems, pinnate fronds.
Nephrolepis. Tender Ferns suitable for growing in greenhouses and as house plants and for planting outdoors in the far South.
Notholaena. Tropical and greenhouse Ferns, growing 12 in. in height, and having slender arching fronds.
Ophioglossum. Hardy Ferns, with small, fronds which can be likened to tongues.
Osrnunda. Hardy Ferns growing up to 6 ft. in height. The spores are produced on special structures on the ends of the fronds.
Pellaea. Greenhouse, evergreen and leaf-losing Ferns, growing up to 2 ft. in height, and having round or hastate spearlike pinnules (leaflets).
Platycerium. Cool greenhouse and tropical Ferns, having divided fronds like the Elkhorn or Staghorn.
Poly podium. A very large group of Ferns, in which are sometimes included Goniophlebium, Dictyopteris, Phymatodes, Pleopeltis and Drynaria. They are found in many countries, and have pinnate feathery fronds, varying in shape and size.
Polystichum. A group of tender and hardy Ferns most of which have bipinnate fronds and are decidedly ornamental.
Pteris. Tropical, cool greenhouse and hardy ferns. Pteris cretica, with ribbon-like fronds, is a typical kind.
Trichomanes. Tropical and cool greenhouse Ferns with semi-transparent fronds averaging 12 in. in length. They require densely shaded, moist positions.
Woodwardia. Hardy and cool greenhouse evergreen Ferns with scaly, pinnate fronds.