Q - My peaches and grapes do fine for me but birds go after them before they are ripe enough to pick. Can I pick them early and let them ripen indoors?

A - To be at their best, peaches should stay on the tree until they start to turn soft. When picked a little early they will turn soft and have good flavor if kept in a cool place out of the sun. It is at this stage they are usually picked for sale at roadside stands.

Grapes should not be picked until fully ripe. They will not sweeten after being picked. A taste-test is the best guide to their ripeness. Pick them when the flavor suits your taste.

Q - I received two violets for my birthday last year and they have bloomed only once, beautiful foilage but no blooms. Why?

A - Insufficient light is probably the most common reason for failure of African violets to bloom. If the light is extremely dim, the plants may grow well, but will flower little if at all. If light is too intense, flowering may continue for a while but eventually devreases.

The length of time the plant is exposed to light also affects growth and flowering. A plant may receive the proper amount of light for only several hours a day but not receive enough total light. A plant in another location may be receiving light of less intensity grow and bloom better.

Generally, they should not be exposed to direct sunlight. However, during the winter some direct sunlight in the early morning will not be harmful.

African violets grown in a window naturally grow toward the light. Turn them occasionally to prevent them from becoming one-sided.

A light intensity of around 1,000 foot-candles for about 6 to 8 hours a day will usually produce good healthy plants with plenty of flowers. As a general guide, your hand held over the plant on a bright day should produce a barely visible shadow on the leaves.

African violets can be successfully grown under fluorescent lamps. Although incandescen lamps may be used, fluorescent lamps will give better results. These plants will grow and bloom fairly well under continuous exposure to light; however, the intensity must be considerably less than that given for a 12-hour exposure.

Q - What time of day is best for cutting roses so they last longest?

A - Most authorities say they should be cut in the late afternoon, about 5 or 6 o'clock. At that time they have the greatest amount of stored food.

Q - We have a lot of grass clippings and put them all on the compost pile. They do not decay properly. Do you know why?

A - Grass clippings in a layer one inch deep or more can become a mat which air and moisture can barely penetrate.

A layer of Norway or sugar maple leaves does the same thing, also a layer or Canadian peat when it becomes completely dry after being wet. All of these materials can make good compost if mixed with oak leaves or some similar organic material.

Q - Our 3-year old dogwood has doubled its height but has never bloomed. Is this normal?

A - A 3-year old plant started from seed or cutting of immature growth may not be old enough to bloom. If purchased from a nursery, it may have been given too much fertilizer. The nitrogen stimulates fast growth but inhibits flowering.

FERN WALK

In the National Arboretum, 24th and R Streets NE, paths cross shady valleys and follow a spring-fed stream. On Tuesday and Thursday at 1:30, an Arboretum botanist will take you along these paths, identifying ferns along the way. Stop in the administration building for a map of the grounds so you can find where the tour begins. Call 472-9100.

PLANNING FOR CANNING

It's not too late to think of a vegetable garden you can harvest this autumn. Wednesday, 7:30 to 9:30, a member of the Prince George's Horticulture Extension Service will tell you everything you need to know to start and take care of a vegetable garden.

Then, on August 1 at 7:30, you can bring your ailing plants to the center and get a few tips on how to revive them. Both programs are free, but register in advance. Call 552-1093.