[A] An admirable paper upon the propagation of hardy trees and shrubs from seeds and the treatment of the young seedlings, by Jackson Dawson, may be found in Trans. Mass. Hort. Soc. 1885, part 1, 145, and also in Rep. Sec. Mass. Bd. Agr. 1885, 468.
Sowing.—The soil in which seeds are sown, especially in in-door culture, should be such as to allow of perfect drainage and at the same time to hold moisture. Good potting soil, with a liberal allowance of sharp sand, is the best for general purposes. Pure sand becomes too dense, and leaf mold alone is usually too loose and open. A proper combination of the two corrects both faults. It is impossible to describe a good potting or seed-bed soil. Some experience is essential to the best results in preparing it. It should be of such character that when a damp portion is firmly compressed in the hand it will fall apart when released. It should never bake. Good old garden loam, to which an equal quantity of sand has been added, is usually a good soil for common in-door seedage. There should be no manure in soil used for seeds which produce a delicate growth, as rhododendrons and kalmias. In all such cases, rotted sod or leafy peat forms the best basis. The soil should be sifted and thoroughly fined before seeds are put into it. Seeds usually require lighter soil than that in which the growing plant will flourish. Cocoanut fiber is sometimes used in place of the soil, as it holds moisture, allows of almost perfect drainage, and does not become “sour.” Fine dead sphagnum moss may also be used. Orchid seeds are usually sown on the live moss in which the parent plant is growing; or they may be sown on damp wood or cork. (See under [Orchids], [Chap. VI].) Small seeds, like those of cineraria and calceolaria, germinate well in very old cow-dung obtained from a pasture; the unctuous matters have disappeared, leaving a fibrous remainder. But all things considered, well-prepared soil is the most satisfactory medium which can be used. Seeds of aquatic plants which are to be sown in a pond may be placed in a ball of clay and dropped into the water.
Shallow boxes or “flats” and earthen seed-pans and lily-pans are usually preferable to pots in which to grow seeds. They give more surface in proportion to their contents and require less attention in drainage. If pots are used, the four to six inch sizes are best.
If delicate seeds are sown out-doors, they should be given some protection, if possible. An ordinary hot-bed frame gives the best results. In warm weather or a sunny exposure it will be found desirable to substitute a cloth screen for the sash. A thin or medium water-proof plant cloth, either commercial or home-made, is excellent for this purpose. It may be tacked upon a simple and light rectangular frame which is strengthened at the corners by iron “carriage-corners.” These cloth-covered frames are handy for many purposes, particularly for protecting and supplying some warmth to seed-pans and young seedlings.
It is essential that good drainage be given all in-door seed-pots or seed-beds. A layer of broken pots or other coarse material is placed on the bottom. Many growers place a thin layer of fine dead sphagnum moss or of peat over this drainage material, and it certainly makes a useful addition. It is particularly useful in isolated pots or small boxes, as it holds enough moisture to prevent too rapid drying out, while all surplus water is quickly taken off by the coarse material beneath. Over the moss coarse siftings from the soil may be placed, while on top only the finest and best soil should be used. The smaller the seeds, the more care must be exercised in the sowing.
The proper depth for sowing varies directly with the size of the seed. The chief advantage of very fine soil for small seeds is the greater exactness of depth of covering which it allows. Very small seeds should be sown upon the surface, which has previously been well firmed and levelled, and then covered with a very thin layer of finely sifted soil or a little old and dead moss rubbed through a sieve. This covering should be scarcely deeper than the thickness of the seeds; that is, the seeds should be barely covered. Many prefer pressing the seeds into the soil with a block. Or if one has a close propagating-box, the seeds may remain upon the surface and sufficient moisture will be supplied from the atmosphere. Such fine seeds are rarely watered directly, as even the most careful treatment would be likely to dislodge them. The soil is usually well watered before the seeds are sown, or moisture may be supplied by inserting the pot in water nearly to its rim for a few moments. If water is applied from a hose, a thin cloth should first be spread on the soil to hold it. Celery seeds, in out-door beds, are often sown upon a nicely prepared surface and are then pressed in by means of the feet or a board. Some cover to prevent evaporation should be given all small seeds. This may be a board or a slate slab at first, but as soon as the plants appear glass should be substituted to admit light. (See pp. [11] to [14].)
Large seeds demand much less care as to depth of covering, as a rule. One-fourth or one-half inch is a good depth for most coarse seeds in-doors. If one wishes to gauge the depth accurately, the drills may be made by a planting stick, like that shown in [Fig. 8]. Its flange is made of the required thickness, and it is pressed into the soil until the cap strikes the surface. This is a useful implement in seed testing. Another device for regulating the depth of sowing, particularly in seed testing, is the Tracy planter, shown in [Fig. 9]. It consists of two strips of heavy tin plate about three inches wide, hung upon two wire pivots or hinges some two inches long. At their upper edges and equidistant from either end, the plates are joined by a firm spiral spring, which serves to throw the upper edges apart, and to cause the lower edges to join. This trough is now filled with the required number of seeds, and is then inserted into the earth to a given depth, when the fingers push inward on the spring and the trough opens and delivers the seeds.
