Q: I bought football mums and planted them, but the blooms are not as large as I'd expected. I fertilized them only once. Is that the reason?

A: Disbudding is necessary to get outstanding flowers on mums, dahlias, peonies and tea roses, among others. Removal of all but one bud per stem is required. Small buds should be prinched off when they are no larger than a pea.

Q: My Red Delicious apples are muddy red this year instead of bright red like they were last year.

A: High temperatures are responsible. Apples need cool nights to achieve their best color. This year was too hot and dry for good color.

Q: Can you tell me how to grow leeks?

A: The leek (Allium porrum) is one of several vegetables belonging to the onion family, which also includes garlic, chives, shallots and the Cibol or Welsh onion. The mature plant has a thick stalk or stem about 18 inches high with broad, flat, dark - green leaves. All parts of the plant contain the odor and flavour typical of the onion family, but the leek is somewhat milder than most onions. The edible part of the leek is the stem, which is blanched by covering it with soil to keep it white and tender.

Leeks are a valuable addition to the winter garden since they can be left in the ground and harvested fresh during winter and early spring in areas where temperatures do not go much below zero. They are particularly good in soups and stews.

Plant the seed indoors in March. In April plant the young plants outdoors, three or four inches deep and four to six inches apart. In order to prevent soil rot, fill the hole around them gradually during the season. Eventually plants are also hilled to provide additional blanching. You can start the crop in midsummer. Plants continue to increase in size until late fall.

Q: I've had a while birch for four years, but now it is dying. Is there any way to save it?

A: One of the biggest faults of gardeners is their insistence on planting plants that are not likely to survive in their locality. The European white birch or clump birch is an example. Outside its natural range. It is very susceptible to attack by the bronze birch borer. About the time the birch gets to the point where you can enjoy it, the top dies out. The following year the tree is dead.

The borers overwinter as larva under the bark of the tree. In early May, adults start to emerge and egg- laying begins soon after. Preventive spraying should begin around late May with additional sprays in early, mid and late June. Spray the entire tree.

However, once the tree has been badly damaged, it is too late to save it.

Q: I planted three 2 - year - old apple trees last spring, and they are now five feet tall. Can I put large plastic bags over them to protect them from severly cold winter weather?

A: The trees can be protected with a plastic cover. Build a frame over each one, cover it with plastic and seal the plastic to the ground with soil.

This traps the heat radiated from the soil, keeps the humidity high and shelters the tree from the wind. The plastic must be shaded to keep the direct sun from striking it and building up the temperature inside.

However, the trees should survive without the plastic if given a four or five- inch mulch of tree bark or something similar, shaded from the sun and sheltered from the wind. If hardened properly, they should withstand quite cold temperatures, and the mulch will prevent the soil from freezing deeply.