Bulbs are grown extensively, both privately and commercially, for cut flowers, and for indoor use during the winter season. It is not hard to achieve success in forcing bulbs if two important rules are observed, namely: I. Procure the strongest and best bulbs possible, for good care will improve the quality of the flowers but not the quantity. The latter is always fixed within the bulb before it is purchased. 2. Perfect root development must be insured before the tops are permitted to start growth.
The bulbs should be planted as soon as they are procurable, with late August and November as limits. The soil to use should be rich loam mixed with bone meal in a one to fifty proportion. If the soil is heavy add leaf mold or sand. It is better to avoid manure unless it is thoroughly rotted and pulverized. Five-inch pots may be used for larger bulbs, such as hyacinths; and a three or four-inch pot for one tulip or any bulb other than a hyacinth bulb of large size. It is better, however, to plant three or more bulbs in a larger pot, as soil moisture and temperature are more evenly maintained. When being forced for cut flowers, bulbs are planted in boxes or flats of a depth of three inches to four inches, with the bulbs set from one inch to two inches apart. This is a good way to grow bulbs for decoration also, since the flats can be covered with crepe paper, raffia mats, etc., when the flowers are in bloom. Broken pottery or charcoal should be put in the bottom of the pots for drainage. The soil is then sifted into the pot or flat, but not packed, and the bulb is so planted that the top is just below the surface. Do not press the bulbs down. After planting, water thoroughly to settle the soil firmly about the bulb and do not water again until the top growth starts unless the pots or flats are stored in a place where they will dry out.
After being planted, the bulbs must be stored away in order that they may root properly, because rooting is the most important phase in successful bulb forcing. There are several methods of storage:
2. Pots may be placed in a cool, dark cellar, and will keep well if the soil is kept moist but not wet. The danger here is from drying out if they are not watched at frequent intervals.
3. A better method is to dig a trench one foot deep, put in three inches of ashes for drainage and to keep out worms; put in the pots and fill the trench with soil. During freezing weather cover with rough stable manure, leaves, or straw, to a depth of four inches.
4. Pots may be set out and covered with eight inches or ten inches of leaves, filling in between the pots with soil to maintain moisture.
Early bulbs, such as paper white narcissi and Roman hyacinths will root sufficiently in a period of six weeks. It is much better, however, to leave bulbs in storage for a period of eight weeks. Spanish iris bulbs require a longer period for the formation of root growth than most of the other bulbs. This group is probably the most difficult group to force successfully. They should remain buried in the cold frame or in the pit, with all top growth retarded, until a complete root system is established. When ample roots are formed and about one inch of top growth has appeared, it is time to lift all bulbs and remove them to a semi-dark cellar where they may be kept in a cool temperature with little light to encourage the immediate development of stems and foliage. Avoid, at this period, direct sunlight. After a reasonable amount of growth is secured, place the pots where desired. Bulbs should be taken out of storage in relays to provide a succession of bloom.
There are very few types of bulbs which are adapted for forcing in water. The paper white narcissus is best adapted to this type of forcing. A few of the other types of narcissus may be grown in this way, and occasionally early single tulips, Spanish irises, and crocuses can be successfully forced in water. The best method of forcing bulbs in water is that of setting each bulb in a shallow receptacle, partially filled with sand or coarse gravel, and keeping the water just even or slightly below the base of the bulb. These bulbs should then be kept in a dark, cool place for at least six weeks, and the receptacle should be frequently filled with water, which must always be clear and fresh. After the bulbs have commenced to root they may be treated in the same way as bulbs forced in soil.
Bulbs which have been forced in any manner are of no value for forcing during the second year. Such bulbs should be allowed to ripen their foliage by setting the pots or flats in a cool, light place, and providing them with sufficient water to keep the bulb from drying out until the top growth has ripened and begins to die. These bulbs may then be set in the open ground at the proper time in the autumn and they will produce some flowers during the succeeding year. It is seldom that they will recover their vigour sufficiently to be of value for the purpose of forcing during the second or third year.