Bulb forcing

Bulb forcing

The forcing of bulbs, while not exclusively a greenhouse task, is a sphere of culture which offers very wide scope. For the earliest flowers, specially prepared bulbs are obtained and planted tightly in bowls with bulb fibre with the nose of the bulb showing, or in pots or boxes with fresh soil (which has not previously grown bulbs), planting hyacinths in September and tulips or daffodils in October. Rooting occurs best under low temperatures and this can be readily achieved under a thick insulating layer of moist peat in a sheltered corner of the garden or a vacant cold frame. Further watering is seldom required unless the weather is exceptionally dry, when the peat should be thoroughly hosed.

Bulbs are lifted into a warm greenhouse at a temperature of 55-60°F. When growing shoots are well extended, i.e. 1 ½ —2 in., or, in the case of daffodils, when the flower bud can be felt clear of the neck of the bulb. Keep tulips and hyacinths dark at first, daffodils light, and eventually after 7-10 days when flowers stems are well extended, give more heat and full light. This can be discontinued for later flowering, the bulbs being brought straight into light. Always ensure that the bulbs do not dry out.

Bowls of bulbs can of course be treated in the dwelling house in exactly the same way, or alternatively they can be given the necessary dark treatment in the greenhouse before lifting into the dwelling house for actual flowering.


Bulbs, tulips, hyacinths and daffodils, can be flowered after the same treatment in warm cellars or cupboards at 65-70° F., with artificial lighting, a 100 watt bulb being used for every sq. yd., and operated 12 hours in each 24, the tulips and hyacinths having been given a period of darkness prior to forcing. Daffodils may tend to produce excess foliage under low intensity artificial lighting, especially if temperatures are too high. As has been stated previously, much more interest is now being shown in the whole realm of growing under artificial light.


In addition, of course, bulbs, especially tulips and daffodils, can be planted up closely in greenhouse borders to provide early cut flowers at appropriate times of the year.

Crocus is also a useful flower for greenhouse culture, being planted in pots in October.


These beautiful corms can be induced to flower very much earlier than they would out of doors by planting in well prepared borders 3 in. deep at a distance apart of 6 x 6 in. in February or March. The primulinus type is much more popular for this purpose and Allard Pierson is also an excel-lent early flowering type.


Iris also, especially the varieties ‘Wedgewood’ and Tmperatior\ can be grown in much the same way as gladioli for early bloom, and can also be planted in the autumn for spring flowering, preferably in greenhouse borders 3 in. deep and 3-4 in. apart.


These are most attractive cut flowers for home decoration and, because of modern breeding, they are now available in a wonderful range of colours. They can be grown either from seed or from corms, the seed being sown in April and the corms planted in September.

There are three main ways of growing from seed. The first method is to sow the seed in boxes of moist peat, covered with a sheet of glass and paper, maintaining a temperature of 55-60° F, and pricking off the little seedlings 2 in. apart into 9 in. pots of clay or bituminised paper filled with John Innes No. 2 or U/C Summer Mix compost. Alternatively the seed can be sown direct in the containers, although germination tends to be erratic. Another method is to sow the seed individually into peat blocks, for planting either into pots or greenhouse borders, although this is likely to be less attractive to the amateur as it takes up great greenhouse space and the plants also tend to make a lot of foliage at the expense of flowers. The young plants in boxes or pots are taken outside to stand in a vacant cold frame during the summer, where, if fed and watered regularly, they will make good growth. Plants are lifted into the greenhouse in September when, if given water and moderate warmth, they will soon flower, and continue to produce blooms over a long period. Support with twigs or nets will be necessary to avoid the plants flopping hopelessly.

Sorry, comments are closed for this post.