Q - I have received several African violets from friends and they are all growing well with me. My problem is this: I need to repot some. What is the best potting soil mixture to use? I've seen bags marked "potting soil," but they all have different ratios of contents. For a novice it's all very confusing.

A - Drainage is the most important consideration in preparing a soil mixture for African violets. A poorly drained soil is probably the most common reason for poor root development. An excellent mixture of readily available materials that will provide good drainage for years may be prepared from one part soil (by volume), one part sphagnum peat and one part horticultural-grade perlite.

Horticultural-grade vermiculite or one of the calcined clay materials, such as Terragreen Turface or Lusoil, may be substituted for the perlite and will give equally good results. Although sand is often recommended, it is inferior to the perlite, vermiculite or calcined materials, and has little to commend it.

Sphagnum peat is probably the best source of good organic matter for the soil mixture. It's coarse, resists decomposition and holds moisture well. Other types of peat are less satisfactory because they're too fine and tend to get compact and soggy rather quickly.

Leaf molds and manures are often recommended, but they're too fine and tend to get compact and soggy rather quickly.

Leaf molds and manures aroften contain undesirable substances.

Most garden soils are not satisfactory when used alone even though they will produce excellent plants in the garden. When placed in pots, garden soil does not drain well since it's no longer connected with the natural soil-drainage system. Water passes slowly through it, it soon becomes compacted and little air is left in it.

It's usually not desirable to add fertilizers to a freshly prepared soil mixture, especially if it wll be heat-sterilized before use.

Q - Which is better to use for mulching, pine bark or hardwood bark?

A - The bark you choose is largely a matter of personal preference. Pine bark has a broad flat surface and it does tend to float off in wet places. Hardwood bark can come from at least 20 different species of trees, and the texture of each one will be different. The bark of oak, cherry, maple and gum, for example, will be similar to medium-size pine-bark particles. Hardwood bark may adhere to the soil better than pine bark on slopes or in wet places.

Q - I have a nice 10-year-old asparagus bed. This year for no reason I have not been cutting the thin shoots. Is this a mistake? I read somewhere that you should cut everything during the eating season.

A - If all the spears on a particular plant are thin, some specialists recommend that they not be cut. Allowing them to remain will let the plant produce and alay down more food reserves in the crown for better spears in following years.

If only one or two of the spears of the plant are thin, they should be rrmoved. Any fern growth allowed to remain during the harvest season will delay or stop the development of new spears on that plant and also may attract asparagus beetles.

Crooked and injured spears should be cut and discarded.

Q - A variety of my azaleas is infested with a fungus. I try to pick the fungus off as soon as I see it, but it multiplies very quickly, I have sprayed for the past three years, usually after the blooms have fallen, but it has done no good. Can you help me, please?

A - This is a fungus disease called azalea leaf and flower gall. Infested leaves become swollen, curled and fleshy and turn brown. Infected flowers are fleshy, waxy and swollen. These galls are made up of abnormal tissue. The occurrence and intensity of the disease depends on weather conditions and upon a source of the casual fungus. Spores produced in the whitish mold on the surface of the galls blow and are washed to leaf and flower buds causing infections. When only a few plants are involved, the disease is best controlled by picking the galls and burning them. Do it when they first start to form. Some varieties are more susceptible than others.

Q - I was given a maple tree for Mother's Day three years ago. It's now about ten feet tall. This year it has tiny red balls on many of the leaves. Can you tell me what can be done to save this beautiful tree?

A - The tiny galls on your silver maple leaves are caused by miscropic mites. The galls are first red, then turn green and finally black. Infested leaves may drop earlier in late summer or early fall than uninfested ones. Other than detracting from the attractiveness of the foliage, the galls do not harm. Once the galls are formed, they can't be removed because they're part of the plant. They can be prevented by spraying the tree with lime sulfur in early sping just before the buds start to open, but generally it's not worth the effort. If you do spray, directions on the label should be followed closely.

Q - We have a lot of spiders in our small green-house and are afraid they will damage the plants. Can you help?

A - Congratulations. Spiders are helpful friends of gargdeners, indoors and out. They devour an incredible number of harmful insects, including whiteflies. When you see spiders in your greehouse you can be certain they are there because there are insects for them to eat. Spiders will do no harm to you or your plants.

Q - Four years ago I dug up three American hollies in the woods and planted them in my back yard. How long does it take for them to bear berries and how can you tell the male from the female?

A - Whether the tree is male or female cannot be determined until it blooms. The female usually blooms and starts to bear berries when 10 years old; the male blooms when about eight years old, but does not bear berries. CAPTION: Illustration, no caption