Forcing Spring

  • Post published:12/11/2008
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Once upon a time the only bulbs that anyone thought of forcing and bringing into bloom during the dark days of winter were paperwhite narcissus. And very nice they were, delicate and elegant and subtly fragrant. Who would not want a bowl of these beautiful pale flowers in a cozy room while the snow is falling outside the window?

I have forced many bowls of paperwhites and been delighted each time, but I have learned over the years that the same principles that allow us to force narcissus, apply to any number of hardy bulbs including crocuses, snowdrops, tulips, grape hyacinths, and hyacinths. In fact there are special glasses designed just for forcing large hyacinth bulbs.

The basic principle is to trick the bulbs into thinking that winter has come – and gone – by chilling the bulbs in the dark for four to six weeks and allowing roots to develop, just as if they were out in the wintry garden. Then let them feel that spring has arrived by bringing them into a cool bright room so that shoots and leaves will begin to sprout, and then come into bloom.

One of the common ways to force bulbs is by putting two inches of attractive pebbles in a shallow decorative bowl. Add water to just below the level of the pebbles. The bulbs should be set into the bowl carefully so that they do not touch each other; add enough more pebbles to hold the bulbs upright and in place as they begin to sprout.

The bulbs must never sit in water, but the roots must be able to grow into the water. While the bulbs are chilling (temperatures between 35 and 50 degrees) it is wise to periodically check them to make sure that the bowl does not dry out.

A hyacinth glass is designed to hold the bulb away from the water, while the roots grow down into the glass. A row of these can make a very pretty display. Recently a reader told me she thought hyacinths worked much better as forced bulbs than they did in the garden, and I have to say I completely understand her point of view.

Any decorative bowl will do, but I like glass because I can see the water level, and not worry about it. Others have used glass vases for narcissus so that there is no worry about staking. The sides of the vase hold the stems straight.

Bulbs can also be planted in soil in pots. There are even special pots called bulb pans for just this purpose. They are wider to accommodate several bulbs, but shallower, only about five or six inches deep. However, the principle is the same.

When I say soil, I really mean a soilless mix that has a little added peat moss and perlite. Bulbs have stored all the nutrition they need to bloom. No fertilizer is necessary.

It seems to me that tulips are usually forced in pots, because they are larger and heavier flowers. Pots of white or red tulips at Christmas, or Valentines Day for that matter, are really stunning.

I do have one caveat about forcing tulips. I potted them up one year and had them cooling in the basement. When I thought it was time to bring them into the light I found that mice had made a good meal of them. I had totally forgotten that daffodils are poisonous and therefore unattractive to all wildlife, but that tulips were not. For the first time I understood why some people chilled their bulbs in the refrigerator.

If you put your bulbs in the refrigerator, use a mesh bag, not plastic. You can use the crisper drawer, but not if it also contains ripening fruit, or vegetables. They will give out a gas that will damage the bulbs.

Once the bulbs have been cooled in the dark and developed good roots it is time to bring them into the light. Remember how spring arrives? Slowly. The potted bulbs should not be brought directly into a very warm sunny room. Bring them into a cool bright room and allow the shoots and foliage to develop and grow. Keep turning them so that they grow evenly and don’t start leaning toward the light source.

When they are budded they can be brought into a warmer room – if you have one – for a more general enjoyment of the flowers.

Many of us are keeping our houses cooler these days, which is not only economical, but also good for our forced bulbs, and many other houseplants. In the past I have kept my blooming bulbs upstairs in the bedroom where it is cooler because the flowers last longer, and then bring them downstairs when we are having company.

People often ask me if they can put the bulbs they forced in the garden come spring. Of course, they can, and I often do, but there is no guarantee. Nothing to be lost either. Just remember to keep the plant in the sun so the foliage can gather some strength, even it is someplace you don’t have to watch it.

There is a fragility and tenderness about forced bulbs that is different from other plants we might have blooming indoors during the winter. Somehow that seems appropriate for the tender days of a new year when the light is beginning to grow again.

November 8, 2008

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