Indoor Tulips: Tulipa
The amateur will plant tulips either in pots or bowls containing bulb fibre or into a compost of, sand and one-third part by bulk of peat or leaf mould. Peat is almost sterile and contains neither disease nor weeds. Make the peat thoroughly moist before mixing with the soil, otherwise it will be impossible to bring to the desired moist condition after the bulbs are planted. Four or five bulbs to a bowl is usual and they should be of the 4-1/2 in. (12 cm) size, as used by the commercial grower. When set in the bowls, the tops should be just covered with the compost. It is advisable to line the bowls wilh a layer of peat which will help , and to the compost, to keep it sweet, should be added several small pieces of charcoal. Handle the bulbs carefully as tulips bruise easily. After planting, water lightly so that water remains in the bottom of the bowl to stagnate; then place in a darkened cupboard or in the cellar.
Bulbs should be introduced to heat and light gradually. Usually, failures are the result of the bowls being taken from darkness and a cool place and plunged immediately into the strong light and warmth of a greenhouse, or large, sunny window. The commercial grower too, is all too often guilty of this in his desire to have the bulbs in bloom in the shortest time. At first a temperature of 48°F (9°C) is sufficient and this can be gradually increased to 60°F (16°C) by raising it about 1° each day. Likewise where a cool house is being used for growing on the bulbs for cutting in boxes. These will generally follow, which will have finished flowering by the year end. The Darwins will be used and they may be taken indoors early in January to bloom in March. When first introduced to the greenhouse they should be shaded either by hessian canvas nailed to the sash bars of the house, or by sheets of brown paper placed over the boxes. The shading may be removed after ten days, though in a house where no heat is used, hessian stretched over the inside of the roof will help to keep out frost and should remain in position until early March when the spring sunshine will bring the bulbs into bloom.
In the heated greenhouse, the temperature may be raised to 65°F (18°C) for all forcing varieties as soon as the green flower buds are observed, but at this temperature opening of the buds will be rapid and care must be taken to see that they are not too open before marketing.
As a rule, the short-stemmed varieties should be given some shade almost throughout their period in the greenhouse, while the Darwins and long-stemmed varieties should be grown on without shade under forcing conditions. In a cold house early spring cultivation may be helped by the use of hessian to keep out frost, but this should be discarded as soon as possible. For this reason, tulips grown in the semi-shade of the living-room should be confined to the short-stemmed varieties.
Care must be taken when growing on a large scale, to determine the exact forcing requirements of each variety. It will not do to select a variety for forcing merely because its colour is attractive. For instance, the striking golden-yellow, flushed red variety, ‘Prince Carnival’, will not stand forcing at all and if early bloom is required, select the orange ‘Prince of Austria’, which may be forced at a temperature of 80°F (27°C), whereas for most Darwins forced for cut bloom, the maximum temperature should be about 58°F (14°C). Fluctuations in temperatures will be fatal to bulbs being forced. A temperature of 55°F (12°C) kept constant is far better than one which might fluctuate between 50°-65°F (10-18°c). Draughts in the home may cause the formation of a badly drooping bloom or of a yellowing of the foliage. The same troubles will be experienced where greenhouse temperatures fluctuate too much. If the air in a warm room or greenhouse falls suddenly, the rate at which the plant loses water by evaporation is slowed up. The roots, however, continue to work in the warm soil taking in water which cannot be transpired. The cells of the plant becomeand cannot support the bloom with the result that it falls over, making it a total loss. Careful watering, correct ventilation and even temperatures make for successful tulip forcing.
The commercial grower will use mass-production methods to plant the bulbs which work out more cheaply in proportion to the number of a variety purchased. The bulbs will be set out in bulb boxes made up of wood 1 in (2.5 cm) thick and 6 in. (15 cm) deep and of a size which can be comfortably handled and which will hold about 3 dozen bulbs. A 1 in. (2.5 cm) space must be left between the bulbs so that correct air circulation may be allowed, for remember that bulbs being forced must contend with conditions of warmth and high humidity, both of which will encourage disease unless correct ventilation is provided. Bulb boxes should be drilled with holes, one to every 6 sq. in., (15 sq. cm) to make for correct drainage for the boxes are placed in the open exposed to the often wet weather of late October and early winter.
Clean virgin loam to which has been mixed some coarse sand and moist peat should be used, the soil should preferably have been taken from a depth of 10 in. (25 cm) to ensure almost complete freedom from disease and weed seeds. The bulbs should be planted with the tops just below the soil level. The boxes are then placed outdoors over a bed of boiler clinker or similar material to ensure drainage and where they may receive some protection from strong winds. Over the boxes is placed a 4 in. (10 cm) covering of weathered ash, sand or soil to exclude the light and to protect the bulbs from drying out. They will rarely need any artificial watering, rain and heavy dews providing all that is necessary. They will remain in the open until the correct times for taking into heat or the cool-house. The covering of soil or ash is then knocked completely away, taking care not to injure the growing points of the bulbs which will be about 2 in. (5 cm) tall. The gradual introduction to heat and light is essential.