GARDEN : Forcing the Issue : How to Get Bulbs to Flower in Time for Christmas

ONE OF THE benefits of growing bulbs in pots and bowls is that you have a measure of control over their life cycles and consequently their flowering periods. It is quite a boost in the dark days of winter to witness the emergence of the sweetly scented blossoms of the paper white narcissus or the sentinel-like columns of brightly colored hyacinths. With consistent cultivation, it’s not difficult to have many different bulbs in full flower at Christmas, provided that you follow a few basic rules and select the suitable varieties.

It is important to start thinking about Christmas-flowering bulbs during early fall. Your choice is somewhat limited for very early flowering because only hyacinths respond properly to advance preparation, and the varieties of narcissus and tulip that can be used are relatively few. However, among the wealth of early-flowering bulbs such as snowdrops, crocus, chionodoxa and scilla, are many kinds that can be persuaded to flower early; they need only be afforded some protection.

Early planting is essential, because forced bulbs require that they must be buried in a bed of peat or ashes outdoors in cool conditions for about 10 weeks. That enables them to establish a good root system before being subjected to any unnaturally high temperatures. If successful root growth is not achieved, the plants often will collapse when taken out outdoors into the warmth and light. It depends upon the variety, but most bulbs take at least three or four weeks to reach the flowering stage after being brought indoors. So for successful Christmas flowering, all bulbs must be planted by early fall.

Use bulb fiber, especially if you are planting your bulbs in a bowl or container that does not have drainage holes. Bulb fiber is a coarse medium, made up largely of fibrous peat moss but with charcoal and oyster-shell grit incorporated. It contains virtually no nutrients, so the bulbs are largely dependent on their own resources. Small bulbs such as snowdrops and chionodoxa are better off in a straightforward potting compost, ensuring the most compact and stable habit of growth and enabling the bulbs to retain sufficient energy to still be a viable proposition when planted out in the garden after flowering is over. Hyacinths and tulips thrive in bulb fiber but are rarely worth planting in the garden after being forced. Some narcissus can be used for naturalizing; the popular Christmas-flowering paper white variety is tough enough to withstand the vigors of open-ground cultivation in this region.

Small bulbs, including tulips and narcissus, should be planted in the pots or bowls in which they are to flower. Hyacinths are best planted in boxes to begin with, unless you are growing only three bulbs in a single bowl, in which case direct planting is necessary. Of all the Christmas-flowering subjects, hyacinths are the most popular, but they are not the easiest bulbs for achieving a visually attractive result. Often the flowers open at different times and the heights are variable. That is why box culture is advocated at the outset. Provided that a single variety is grown, the different plants should make progress at an even rate and flower at a given time. Variation within individual plants will ensure that in practice this won’t happen, but by growing only one variety you are going to come as near to that ideal as possible. By establishing the bulbs in a box, it is possible, before introducing the bulbs to the light and warmth of the house, to lift those of similar stature and state of growth and plant them in bowls together. If you take a sharp knife and cut through the matted root growth, the bulbs can be easily lifted with a cube of root and will grow on without check.

When the bulbs have been planted, take the pots or bowls outdoors and cover them with a generous layer of peat or ashes. Or place them in a cool, dark place in the home--in a cupboard under the stairs, say, or in the garage. If you leave them indoors, check regularly to see whether they need watering; those outdoors generally receive enough moisture naturally.

Leave the bulbs undisturbed for at least 10 weeks before bringing the pots in. At this stage the bulbs should be showing bold, yellowish shoots, which will quickly turn green when exposed to sunlight. Clean the pots up. In the case of hyacinths, you might like to add a small fern to the center of the bowl. Those popularly used in the flower trade are Pteris tremula and P. cretica albo-lineata . Those are often sold also for bottle gardens and can usually be picked up as small plants at nurseries.

When forcing bulbs, the tendency is to want to apply a lot of heat in order to hurry them along, especially if you are trying to achieve flowering by a given date. High temperature results in the etiolation of the stems and leaves, together with the collapse of the blossoms. What is required is a balance of heat and light intensity. Winter light is poor, and it takes

relatively little warmth to throw plant growth out of natural balance. Ordinary room temperature demands that the emerging bulbs be kept in full light in a west- or south-facing window throughout the daylight period. If the bulbs still start to look drawn, then put them in a cooler room, at the same time providing them with the maximum daylight possible.

Fertilizing also can distort growth. It used to be thought that fertilizing could be undertaken successfully with indoor bulbs only from the time that the buds were showing color. Certainly, considerable benefits have been conferred upon bulbs treated that way, using either a traditional multipurpose liquid fertilizer or a tomato fertilizer every two or three weeks until the foliage has faded away. It helps rebuild the exhausted bulbs for next season and makes it worthwhile to plant them out in the garden for the following year. That is not true, however, of hycainths, which generally deteriorate so badly after being forced that they are not worth planting in the garden. If they do flower the following spring, the heads are usually distorted, with the individual blossoms far apart on the stems.

Recent experiments have somewhat altered our views on fertilizing regimes. It has been proved that, apart from hyacinths, much better flower and foliage quality can be obtained by feeding from the time that the bulbs are brought into the light and warmth. Hyacinths respond negatively, producing large, rank leaves and long, twisting, serpentine flower stems; they grow completely out of character and are ruined for the purposes of display. The substitution of potting composts for bulb fiber in all cases except with hyacinths also indicates that where nutrients are readily available, the plants make better progress. A note of caution, though: If you are using a potting compost for your bulbs, go easy on the liquid fertilizer. Over-fertilizing produces soft, unnatural growth that is vulnerable to every disease going.

Once forced bulbs have finished blooming, they should be discarded, because even though it is possible to take care of them until the foliage fades, in practice they are neglected once the floral show is over. If you are not prepared to give your bulbs the attention they need after they flower, then don’t bother. The gardens of the world are littered with poor, weedy bulbs that have been tipped out of dried-up compost from bowls and have never made the grade again. Most will come around in a couple of years if pampered, but it is best to separate the outdoor display from the indoor enterprise and plant good bulbs in each, rather than use the garden as a repository for the retired inhabitants of the windowsill. If you feel that you must plant exhausted bulbs out, then do not do so until the foliage has faded and the bulbs have become dormant. Even though the popularly forced varieties of bulbs are hardy, their foliage is very vulnerable to damage when raised in warmth and then taken out into the cold spring air. Damaged foliage will affect the efficiency of the storage system in the bulb--vital if a show of flowers is hoped for the next season.