Indoor Gardening: Winter Bulb Forcing

Posted on 14th April 2011 in Flowers, Gardening

The bright color of spring bulbs is even more dazzling when you bring it into your home on a gray, drizzly winter day. This luxury is easy to achieve if you force a few of your spring blooming bulbs.

Forcing seems too strong a word for persuading bulbs to bloom earlier than they normally would. By controlling the temperature and light conditions to simulate an early winter and spring, the bulbs are convinced (induced) to bloom when we want them to, rather than at their normal time. Forcing is easy when you understand the four stages involved.

Stage one is dormancy. Your bulbs will be dormant when you get them. When a bulb is dormant there is no visible change, but inside, the flower buds and leaves are busy developing.

Stage two is root growth. This varies from one type of bulb to another. If the temperature nears freezing, development slows down, and if the temperature rises toward 55-60 degrees the top growth will start. If bulbs don’t get enough cold, their stems will be short and weak, letting flowers flop over or drop off.

Stage three is top growth. At this time the pots of bulbs should be moved to an enviroment with strong light (not direct sun) and temperatures of 55-65 degrees.

In 3-4 weeks the bulbs will reach stage four, flowering. Set them in a 75 degree room where they will get plenty of light but no direct sun. Cool nights are beneficial. Keep them away from heat sources, and water them well.

General Instructions

Plant your bulbs as soon as you get them if possible. If you can’t get them planted at once, store them in the refrigerator, but away from ripe fruit.
Fill the container so that when you place the bulbs in it, their tips are even with the rim of the pot. Gently finish filling the pot to the top and water it thoroughly. This will settle the medium enough for future waterings.

A single bulb should be put in a container just a little larger than its circumference. A six inch pot or bulb pan will hold six tulips.

Bulb pans are special containers for forcing bulbs. They are half as tall as they are wide, and are designed to hold tall plants with less risk of tipping over. Regular pots can also be used, as well as bowls or other decorative containers. If you intend to keep the bulbs after forcing them, they should be potted in soil or a soil mix, with a little bulb fertilizer. If you don’t plan on keeping them, any porous material that will keep the roots moist but not soggy, will do. The bulbs must not be allowed to dry out.

Planted bulbs should be stored in cool areas, 35-50 degrees. They can be put in an unheated basement, greenhouse or garage, a crawlspace, or a coldframe. Or the containers can be buried in a trench in the ground. Line the bottom of the trench with gravel to improve drainage, and cover with sand, hay, sawdust, etc. (remove the covering gently so you don’t injure tender sprouts). They should be kept slightly damp during this period. If mice are a problem, cover the pots with wire.

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