DAHLIAS and chrysanthemums are two of the most popular fall flowers. The mum is recognized more or less officially as the queen of autumn flowers and the dahlia definitely is a close runner-up. These two floral types can justifiably boast of as great a diversity of form and color as any comparable kind of plant life.

Dahlias and mums are highly effective for indoor decoration during the fall season. You can enjoy the cut flowers even though your garden is bare. These two flowers are among the most popular florist subjects during the next few weeks. How long the blooms last depends on the treatment they receive after being removed from the parent plant.

If properly handled both mums and dahlias will last for many days ... often more than a week ... when displayed indoors. It is best to cut the flowers early in the morning. The second best time is late in the evening. During the early morning hours the plant cells are turgid with the moisture stored up during the previous night. Blooms removed at that time usually suffer a minimum of shock.

The cutting tool used, whether a knife or 'pruning shears, should be clean and extremely sharp. If the cut produces a mashed or ripped stem end, then the flower's longevity may be seriously curtailed. The life of a flower after it is removed from the plant depends on the ease with which water is absorbed into the stem. This is difficult when the stem ends are mashed and ragged.

It is best to cut the stems on an angle, rather than straight across. It is difficult for water to move into the stem ends when they stand on a solid base; the angle of the cut facilitates rapid movement of water up into the stem.

Mums keep best if the flowers are cut after they have attained complete maturity. However, open center specimens should be cut before they open fully. The wood that is cut into in separating the stem from the plant should be fairly soft; if not the flower's keeping qualities will be greatly impaired. Varieties that are subject to wilting should have the stem split about four or five inches along the base. Scraping the outer skin at the base also aids in greater moisture absorption.

The longevity of both the dahlia and mum will be improved by dipping the stem end in boiling water for about one minute. Then place the flowers in a deep container filled with cold water to a point just below the flower head. Allow the blooms to rest in this manner for several hours before arranging them.