Q - My rhododendrons bloomed beautifully this year, and there are a lot of them; is it really important to cut off the faded flowers?

A - Rhododendrons growing wild in the Appalachians bloom beautifully every year and no one picks off their faded flowers. However, if faded flowers are allowed to stay on and form seed pods, the vitality of the plant will be lowered because food (energy) utilized in seed production would be lost. One rhododendron authority estimated that forming seeds pods uses up seven times as much food as the development of flower buds.

Q - I want to take a lot of azalea cuttings and root them. What is the best rooting medium to use?

A - In general, there is no one ideal rooting medium, but several combinations of materials can provide a good workable medium, according to Carl E. Whitcomb, Oklahoma State University horticulturist. Peat and perlite or peat and ground bark on a 1:1 basis is very good. It is very important that these components are free of diseases and insects. Perlite and vermiculite are sterile when purchased. Good-quality peat moss, although not sterile, is clean and ready to use direct from the bale. Ground pinebark or sand should be treated with either steam or methyl bromide to use. The open wound at the base of the cutting with a warm-moist environment is an ideal entrance for several diseases.In most cases, if a disease is present, the cuttings will die while still in the process of forming roots.

Q - Is it necessary to remove the clippings every time we mow the lawn?

A - If there is a very large quantity of clippings, perhaps some of them should be removed, but in the summer there's not usually that much. Collecting the clippings removes large amounts of materials that can be recycled and provide fertilizer for the grass if left on the lawn. One specialist says that collecting clippings from two or three mowings following the application of fertilizer can remove as much as half the fertilizer applied.

After fertilizer is applied and washed into the soil, the grass plant takes up some of it and transports it to new leaves. Collecting clippings removes many of these new leaves along with the fertilizer stored in them.

Grass clippings allowed to remain on the lawn readily decompose and provide fertilizer for grass growth. Letting the clippings remain does not increase thatch buildup because they quickly decompose.

Q - I planted marigolds in my vegetable garden, just in case. Is it true they will keep insects away from the plants growing near them?

A - They may or they may not. We can find no data to prove or disprove the value of it, but most specialists appear to doubt that they provide such protection.

Research has shown that marigolds can provide some protection from nematodes. These are soil eelworms, so tiny they can barely be seen with the naked eye. Research has shown that they may be causing more lawn damage than experts had thought possible. For example, it was discovered they were causing chlorosis, stunting and bare spots on two famous lawns - The Plain, the parade ground at the U.S. Military Academy, and Arlington National Cemetery.

Research at the University of Georgia showed that growing marigolds in an area all summer would provide protection against nematodes the following year but not during the current year.

Q - Is it a good idea to plant some new tomato plants along about now for a larger crop in the fall?

A - There are three types of tomato plants: Determinate, indeterminate and semi-determinate. The fruit of the determinates all ripens at once. The indeterminates bear fruit over a long period and are stopped only by frost, assuming they get fairly good treatment. The semi-determinates vary.

If you have enough indeterminate or semi-determinate plants, they will continue to provide an adequate crop until frost. If you have determinate ones, it would be good idea to plant some more now.

Q - This spring our 10-year old pink dogwood had dirty white or faded flowers. Is there anything I can do to bring back the original beautiful pink?

A - The pink dogwood usually is grafted onto white-flowering understock. The pink-flowering part of the tree may be dead or dying and you now have growth of a white dogwood in its place. If that is the case, you will never get pink flowers again.

Fertilizing in early spring with 5-10-5 will help the tree grow, as will watering during prolonged dry weather.

Q - Can butterfly bushes be grown from cuttings?

A - Yes, take cuttings in July or August from side-shoots.

Q - Is Sevin safe to use on strawberry plants to get rid of aphids?

A - Sevin is safe to use on strawberry plants but it will not be effective against aphids. Use Malathion instead. Follow the directions on the label closely; apply in late afternoon to avoid killing pollinating insects.

Q - Should I remove the suckers from my sweek corn or let them grow?

A - Let them grow. Research has shown no advantages to suckering corn.

Q - Is is possible to grow globe artichokes outdoors in the Washington area?

A - One of the few places where globe artichokes grow well outdoors is along the California seacoast. The growing season in the Washington area is not long enough.

Q - I have tried three years running to grow white potatoes in my vegetable garden without success. They start out fine but later on dry up and die. Do you know what the problem is>?

A - White potatoes are susceptible of several different kinds of diseases and insects, and it appears to be almost impossible to get a crop without spraying them a regular intervals from the time they are a few inches high until maturity.

To start, it is important to buy certified seed potatoes. This will provide some protection against some of the diseases. They should be planted in acid soil to help prevent a bacterial disease called potato scab. They do much better in light sandy soil than in heavy clay. They need to be fertilized occasionally and watered during dry weather.

Q - The top two feet of my 15-foot Chinese juniper turned brown almost overnight. What could have caused it? It was such beautiful tree.

A - It probably was due to someone in the neighborhood spraying with a week-killing chemical such as 2,4-D. With even a little bit of little bit of wind, the chemical can be blown and cause serious damage a block away. To prevent it, preach and practice: Do not spray with such chemicals when the wind is blowing! Tomato plants and grape vines are particularly susceptible to damage from 2,4-D.

Q - My garden faces north and gets little sun in the upper end and the green moss is thick. I take it off, turn the soil, cover the ground with peat, use lime and weedkiller but still it comes back. How can I get rid of it?

A - Moss is found in soil of low fertility, high acidity, poor drainage or other wet conditions, too much shade, soil compaction, poor air circulation or a combination of these factors. The only permanent solution is to correct the conditions that favor it.

Q - My lawn looks awful. I fertilized it this spring and that can't be the trouble. Could it be a disease?

A - When grass is allowed to get too tall, too much is removed when it's mowed. Loss of more than half the food-producing green sends grass into shock, making it much more susceptible to leaf spot diseases. If the lawn looks whitish the day after it is cut, the mower is too dull. Rotary mowers may need sharpening after almost every mowing.