Flower buds of trees and shrubs that bloom in the spring are formed during late summer and fall. After a period of cold (called their "chill requirement"), they're ready to open when warmth and moisture are adequate. At least six weeks of cold temperatures (below 40 degrees F.) are usually needed before the buds can break dormancy.

If you're tired of cold winter weather, you can bring a bit of spring into your home at this time of the year. Cut some branches of flowering woody plants, bring them indoors, put them into water and after a period of time, varying with different kinds, they should bloom.

Plants differ in the amount of cold weather they need before they start to grow again. Forsythia sometimes blooms in the fall, so you can guess its cold weather requirement is short; pussy willow is another of the earliest to be forced. Then come Japanese quince, flowering almond, cherry and spirea.

Branches should not be cut when the weather is quite cold; if they are cut when the stems are frozen, thaw them gradually by running cold water over them.

They require high humidity, which can be provided by placing the branches in deep water and wrapping them with newspapers. Don't wrap them too tightly, because the opening flowers can be damaged. Keep them at 65 degrees to 70 degrees and remove the covering when the flowers start to open.

Taken now, forsythia should bloom in about two weeks. A month from now it will take about a week.

Look the branches over carefully to determine which contain a lot of flower buds, and select those that are well budded. The larger, fatter buds are usually flower buds, but smaller ones leaf buds.

In the early stages the branches don't need much light. When the buds swell and are almost ready to open, they need good light but not sunlight. When the buds start to show color, take the branches out of the container and put them in jars of water for display. Keep in a cool place at night and during daylight hours when you're not at home. They should last about 10 days.

Cornelian cherry, which produces tiny yellow flowers, needs from nine to 14 days to bloom indoors. Japanese quince, with red, scarlet, rose, shrimp pink, almost orange, salmon and white flowers, takes about two weeks to come into bloom -- but don't hurry them with too much heat. Crabapples and peaches do better if cutting is delayed until March in the north, earlier farther south. Q: Can you tell me how to force tulip into bloom? I live in an apartment without access to a garden.

A: Plant the bulbs in pots with drainage holes. The potted bulbs need 12 to 14 weeks at temperatures ranging from 35 degrees to 48 degrees F. This can be provided in a cool cellar, garage, outdoor shed, dark closed next to an outside wall, or refrigerator.They must be kept in darkness and watered regularly. After 14 weeks the roots should be well developed and sprouts should be two to three inches tall. Put them where the temperature is 60 degrees to 65 degrees F., with fairly good light, and water regularly. When the stems get taller, move to 65 degrees to 72 degrees. Q: We have two large split-leaf philodendrons in our church sanctuary, which is heated only twice a week; it gets quite chilly at other times. Will they survive there?

A: The split-leaf philodendron (Monestera deliciosa), like most other tropical plants, needs daytime temperatures of 70 degrees to 80 degrees F. and 60 degrees to 65 degrees at night. At lower temperatures it will be damaged -- the lower the temperature, the greater the damage. Q: My father taught me to punch holes in the ground to fertilize a tree. Is it necessary to do it this way?

A: F.R. Grouin, University of Maryland Horticulturist, says: "Over the years I have given deep root feeding serious thought and I question its contrast use. Mother Nature has been feeding her forest trees simply by dropping leaves on the ground. These rot and release nutrients into the soil and back to the roots." Q: My peonies had only a few flowers on them last summer. What do you think they may need? A: The food for this year's initiation of growth and flowers is produced during summer and early fall of the previous year and stored in the roots. The food is produced by the leaves by the process of photosynthesis. If the peonies had to compete with weeds, or suffered from want of water, or were partially shaded by the branches of trees or shrubs, then food production would be low and flowering correspondingly poor the following year. Q: Is it safe to use sewage sudge to improve the soil in my vegetable garden? A: Sludge is a good fertilizer because it contains nitrogen and phosphorous, and the organic matter serves as a soild conditioner. The problem is that sludge contains small but variable quantities of toxic metals, according to a report to the Environmental Protection Agency by a group of scientists. Cadmium, the metal of greatest concern, originates mostly from industrial operations and is found in greatest concentrations in sludges from certain industrial areas. Many sludges contain only very small quantities of cadmium and may be used, the report said. Q: How can we keep Irish potatoes the year around? A: It can be done only with refrigeration. Storage time can be lengthened by extreme care in harvesting. Do not skin or bruise the potatoes when digging them up. Cure them in a shady, well-ventilated place for two days before putting them in storage. They can be stored for several months in a cool, dark basement. Q: I intended to fertilize my oak tree in early November but failed to do it. Can I do it now or should I wait until next fall? A: The best time is mid-fall to early spring. It should not be done when the soil is frozen or too wet to work. Q: I have a snake plant with a lovely flower on it. Is this something pretty unusual? A: It's pretty but not unusual. There are about 34 different species of Sansevieria (which includes the snake plant) and all of them have been known to bloom. The ones that bloom more often are the ones that receive good care.