The quantity of seed to sow in order to secure a given number of seedlings will depend also on the quality of the seed and on the soil and weather conditions at the time of sowing. The quality of seed varies much in different years and from differ ent trees. The only way to be at all accurate is to test the seed, but as this is troublesome, and as the seed of most of our common trees is very cheap, it is seldom practiced, and growers simply plan to sow two or three times as much seed as would theoretically produce the number of seedlings desired.
The number of seeds in a pound varies greatly with the size of the seed and dryness. In the case of the birch there are perhaps four hundred thousand; in Scotch, shortleaf and red pine and Norway spruce there are perhaps seventy thousand ; in white pine about thirty thousand ; in box elder and white ash about ten thou sand ; in basswood and sugar maple about eight thousand ; in soft maple about four thousand ; in black walnut twenty of the dry nuts in one pound, and in hickory nuts forty to sixty in a pound.
Raising coniferous trees from seed.
The land selected for the seed should have a light, porous surface soil, preferably underlaid with a moist subsoil that will not dry out easily. It should be so located as to have good circulation of air over it, that the plants may dry off quickly after rains ; and it must be so shaded as to keep off about one-half of the sunlight. In practice, we aim to secure these conditions as follows : A piece of well-drained, rather sandy soil in an airy place is selected and laid out in beds four feet wide. In May, or later, the seeds are sown rather thickly (about three good seeds to a square inch), either broadcast or in rows, and covered with about one fourth inch of sandy loam and then with about one inch of dear sand. Before the seedlings break the ground, a permanent framework at least throe feet above the beds is made and covered with laths. about one and one-half inches apart, running au.th and south. or with sufficient brush to shut out al, Kit one-half the sunlight ; or a movable lath frame may be built, as shown in Fig. 467. If the be 1 is very much exposed to the winds, it should have similar protection on all sides. Under such condition:. or in woodlands where these conditions can be fulfilled, evergreens can be raised with much certainty, while, if seed is sown in the open ground, m st kinds fail.
A cheap and convenient screen can be made from c mutton lath 4 a 4 feet square, leaving a space the width of a lath between each two and nailing the ends between two lath at right angles. Such screens can be made for about thirteen cents each. Sparrows and gophers are prevented from destroy ing the seeds or young seedlings by placing boards along the sides of the beds and then covering the whole bed, screen and all, with small-mesh wire netting.
The most common cause of failure with those who try to raise evergreens is a fungous disease called "damping off," which occurs only while the plants are growing rapidly the first year. The seeds may start well, and the seedlings may grow vigorously for a short time, or until there is a spell of damp weather, and then die off with great rapidity. The use of sand on the surface and plenty of air circulation in moist weather, will largely remedy the difficulty.
Most of the coniferous tree seedlings grow very slowly when young. Many species do not make a growth of more than three inches the first year nor more than five or six inches the first two years. In fact, many species could be planted at the age of five or six years without inconve nience as far as the size of the tops is concerned, but the growth of the roots is more rapid when younger, especially in rich soil. For this reason, evergreen seedlings should be planted out at an age of two, or, at the most, three years, while the roots are still manageahle. Under some con ditions it is passible to plant out one-year-old seedlings, but, as a rule, these are too small for convenient handling or successful growth in the open.
Mulching forms an important factor in the growing of evergreen seedlings. It should con sist of a three-inch covering of straw or leaves, evergreen branches or other material. This mulch should be applied to the seed - bed as soon as the seed is sown, to preserve the mois ture in the soil and to prevent the weeds start ing before the trees. Careful watch must be kept, for if the mulch is not removed as soon as the seedlings break the soil they will all die. On the approach of winter the same sort of mulch should be put over the seedlings to protect them from the sun and from alternate freezing and thawing. This should be removed in the spring after all danger from drying, cold winds has passed.