Tulips In The Greenhouse And In The Home

Possibly more tulips are grown under glass than any other spring flower and this includes the daffodil. Indoor-forced daffodils have to compete with the early-flowering crops from Cornwall and the Scilly Isles, indoor tulips are not forced with such competition and so always prove to be a more reliable financial proposition. Both the commercial grower and the amateur who enjoys tulip bloom in pots or bowls, should aim at providing a succession of bloom from Christmas until the outdoor-grown bulbs are coming into bloom.

Care must be taken to use for forcing only those varieties that can be relied upon to withstand forcing conditions. Almost all dwarf-flowering varieties are suitable for growing in a cool room in the home. The taller-flowering varieties are best left to the commercial grower who uses them for cutting and not for pot culture. For the home, the early-flowering singles and doubles should provide bloom fromTulips In The Greenhouse February until May, for they will be grown under almost cool conditions. The commercial grower will use a forcing-type glasshouse for the single earlies and doubles which will bloom from Christmas until early March, then will come suitable varieties of the Darwin, Mendel and Cottage tulips, though in comparison with the Darwins, there are only a limited number of the other sections used for forcing.

The most important varieties for providing the earliest bloom are the Duc van Thols in yellow and red. They are valuable in that they may be forced into bloom in time for the Christmas market. They are grown entirely for the pot trade, sold either in pots or bowls and presented with the soil covered with green moss – or they are sold separately from the large boxes in which they are forced to those who wish to make up their own bowls. The Duc van Thols are boxed during the last week of September and taken into heat at the end of November. Bulbs should be boxed in flowering sequence. To follow the Duc van Thols, the single early varieties to be taken into heat early in December should be boxed early in October. Later in the month the later forcing singles, the earliest of the double-flowering varieties and the first of the Darwins are boxed.

At the end of October, the later-flowering doubles and the later Darwins are planted. It is important to make a note of the forcing times of the various varieties, ignorance of this is where so many beginners go wrong. For instance, the single early variety Brilliant Star can be taken into heat from a late September planting, during the first week of December – but the deep golden yellow Ursa Minor, though classed as an early single, should not be placed in heat until about February 1st from a late October planting of the bulbs. Some varieties will force after only seven weeks in the plunge bed and early in the season whilst others require twelve weeks for root formation, and are much later flowering. Again, attention must be given to flowering heights. The same Ursa Minor bears its bloom on almost 18-in stems, and is used for cutting, whilst Prince Carnival and Prince of Austria bloom on 3-in. stems. For bowls the 11 in. stem varieties, Fred Moore, King of the Yellows and Brilliant Star, are most suitable and will be in bloom by Christmas if given a temperature of 60° F. or by the end of January in a warm room. ‘Prepared’ bulbs of various varieties will enable them to be forced extra early. These bulbs will have been kept in cold storage in England and must be planted within forty-eight hours of being despatched from storage. The method of ‘preparing’ is to subject the bulbs to

a temperature of 75° F. for two weeks immediately after lifting. They are then kept for eight weeks at a temperature of only 47° F. This cooling not only hastens the appearance of the bloom but also causes more rapid root formation of the bulb when planted in soil. As it is important to use the bulbs within a few hours of coming out of storage, they should be ‘prepared’ in England rather than in Holland.

PLANTING THE BULBSplanting tulips

The amateur will plant either in pots or bowls containing prepared bulb fibre or a compost composed of soil, some sand and one-third part by bulk of peat or leaf mould. I prefer to use peat which is sterile and so contains neither disease spores nor weeds. Remember to make the peat thoroughly moist before mixing with the soil, otherwise it will be almost 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 12 cm. Size, the same size as used by the commercial grower. When set in the bowls, the tops should be just covered with the compost. I prefer to line the bowls with a layer of peat which will greatly help drainage and to the compost, to keep it sweet, should be added some small pieces of charcoal. Handle the bulbs carefully as tulips bruise easily. After planting, water lightly so that none remains at the bottom of the bowl to stagnate – then place in a darkened cupboard or in the cellar.

Those who have a piece of ground attached to the house should always use this for standing out their bulbs. When confined to a small mews house in London for twelve months, I found indoor bulbs provided a valuable mental tonic and I utilized an old cold frame at the rear of the house in which to root the bulbs. I prefer to use pots, for the drainage is more satisfactory and these were stood in the frame until required to be taken indoors to bloom. In this way a succession of bloom could be enjoyed from the early new year until late in spring. A ‘frame’ can be made for a few shillings by placing a deep board round the corner of an adjoining wall and either boards or asbestos sheets can be used for covering the bulbs to keep out not only the light but excess rain. In this way, the bulbs seem to root better and they respond to the change of temperature by coming into bloom more quickly.


Bulbs should be introduced to heat and light gradually. A large proportion of failures are the result of the bowls being taken from complete darkness and a cool place and plunged into the strong light and warmth of a greenhouse, conservatory 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 possible time. At first a temperature of 48° F. is sufficient and this can be gradually increased to 6o° F. 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 chrysanthemums, which will have finished flowering by the year end. The Darwins will almost solely 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 even 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 the hessian stretched over the inside of the roof will help to keep out severe frosts and should remain in position until early March when the early spring sunshine will bring the bulbs into bloom.

In the heated greenhouse, the temperature may safely be raised to 65° F. 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 allowed to open too much before marketing.

If a general rule is required, it is that the short-stemmed varieties should be given some shade almost throughout their period in the greenhouse, while the Darwins and all long-stemmed varieties should be grown on without shade when 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 the various varieties. 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 for cutting, then select the orange red Prince of Austria, which may be forced at a temperature of 80 F. when acclimatized to the warm house, in preference to the much later-flowering Rising Sun, which may be grown to come into bloom when Prince of Austria has finished or if it will fit into the greenhouse cropping scheme more easily.

Again, the two Darwins, William Pitt and William Copeland, may be forced in a constant temperature of 72° F. whereas for most Darwins forced for cut bloom the maximum temperature should be about 58° F. A word should be said about fluctuations in temperatures which will be fatal to all bulbs being forced. A temperature of 55 F. kept constant is far better than one which might fluctuate between 50°-65° F. Draughts in the home will frequently 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 become waterlogged and cannot support the bloom with the result that it falls over, making it a total loss in every way. Careful watering, correct ventilation and a constant temperature make for the success of 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. As this website is intended rather more for the amateur enthusiast than the commercial grower, the wholesale catalogues may be recommended as supplying all the data for the grower for profit. The bulbs will be set out in bulb boxes made up of wood ½ in. thick and 6 in. deep and of a size which can be comfortably handled and which will hold about three dozen bulbs. A 2-in, 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 considerable heat and high humidity, both of which will encourage disease unless correct ventilation is provided. Commercial bulb boxes should be drilled with sufficient holes, one to every 6 sq. in., to make for correct drainage for the boxes are placed in the open completely exposed to the often wet weather of late October and early winter.

A 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 to in. 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, 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 a in. tall. The gradual introduction to heat and light is essential.

Here, a word should be said about the flowering times of the bulbs in relation to the question of fuel costs and the use of a greenhouse for other plants. The grower of pot plants and chrysanthemums for the Christmas market will not find it possible to force bulbs for that market for his other plants will require much cooler conditions. It may also be more profitable to leave out that cold early-January to mid-February period, when considerable fuel will be needed to raise the temperature to 60° F. and coke costs more than L6 per ton at the present time. It may pay better to concentrate on bringing on a crop of cut-flower varieties with an early tomato crop. This means bringing the bulbs into heat early in February and growing in a temperature of about 58° F.

The blooms would be showing colour early in March and would be ready for Mother’s Day and Easter sales. The daffodil must be ready a month earlier to be profitable for by early March it has to compete with the ever-increasing supplies of the West Country The first outdoor tulips do not come on the market until April, so March is a profitable month for the tulip grower. This means that the bulbs should not be boxed until early November, otherwise they tend to form too long and drawn stems. As conditions of partial light so often experienced in the home are conducive to a long stem, the dwarf early and double varieties should be used almost exclusively.

The Mendel tulips are much better for bowl culture than any of the Darwin or Cottage varieties for all of them will force gently, and a number bloom on stems no. longer than 12 in.


Those growing in pots or bowls should cover the soil with green moss at an early date, and most varieties other than the very dwarf Duc van Thols, should have a wire support fixed to each. This will be almost unnoticeable and will keep the blooms in order, preventing any falling over should too dry conditions have tended to force the bulbs up in the soil.

When marketing the pots or bowls, the bloom should just be showing colour so that the buyer may have the pleasure of seeing them open, which they will do but slowly in the cooler temperatures of the home. A sheet of white paper should be fastened round the pot, just enclosing the blooms. They are then sent to market in deep wooden boxes.

Cut bloom should also be marketed with the colour only just showing. Each bunch should contain six, nine or twelve blooms and should have the ends of the stems cut to the same level after bunching. The bloom should first be stood in buckets of cold water for two hours before bunching. The tulip growers of the south-west adopt the method of bringing into a warm greenhouse the buds as soon as the first fraction of colour is noticed. They will have reached just the right condition for marketing within forty-eight hours, and so several days will have been saved by not leaving the buds in the open to reach the marketing stage. Bulbs that have finished flowering indoors should be planted out in trenches with the foliage exposed so that they can die back naturally and they may then be planted in borders for future cutting, though they will be unsuitable for indoor cultivation again. The soil in which the bulbs have been grown should be used in the border but should not be used again for bulb forcing, for the risk of introducing disease. This often occurs with amateurs who can see little sense in throwing out a compost that may have taken some trouble to prepare – it is all too readily emptied into a box and placed in the cellar or attic until the following winter. Fresh soil is essential and more so with tulips than with any other bulb.

For cool-house culture some of the tulip species are most charming when in pots or bowls and they should be much more frequently used for the home, the dwarf habit of many making them just as suitable as the Duc van Thol and single early tulips – they will extend pot culture right into late spring.

With tulips under forcing conditions the most important thing to remember is to increase temperatures gradually, and this means increasing moisture in proportion. Watering has always been a difficulty with both amateurs and commercial growers. A too-dry condition will cause a stunted bloom – too much moisture will cause possible rotting of the roots when the bulbs will be unable to stand up to any forcing. The compost should be moist, but in no way saturated, but if particularly early bloom is required (and that means high temperature) then it is almost impossible to give too much moisture.

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