A Guilford reader received information on a plant spray called Dynogen and wonders if I have tried it or know of its effectiveness. The literature informs him that Dynogen contains a blend of Gibberellic acids which act to promote better growth, flowering and fruiting in garden plants.

Gibberellic acid is, indeed, one of the major plant growth regulators, sometimes called hormones. Its function is mainly in promoting cell elongation. Horticultural uses of the compound range from spraying young bunches of white seedless grapes, producing a more open cluster and longer individual grapes, to spraying geraniums and other plants destined to be made into standards (tree-like specimens).

Undoubtedly if Dynogen contains gibberellic acid in a usable form, there will be visible results from spraying it on almost any actively growing plant. Just the right amount at just the right time might produce a bigger pepper or a red delicious apple with a more pronounced shape. Too much of the hormone could be disastrous for many crops. I’d be extremely careful in trying this product.

A Corinna gardener has had excellent results controlling tarnished plant bugs on zinnias with Sevin insecticidal dust. She has been less fortunate at controlling a stem borer in the same plants and also sunflowers.

Entomology is one course I neglected to take in college. Luckily for me the University of Maine operates a pest management office on College Avenue in Orono. The phone number during normal business hours is 581-3880. Alternatively, gardeners with insect problems can contact their county extension agent who may be able to handle the problem directly or refer a specimen to the Orono office.

A Millinocket gardener has a clematis which was beautiful for several years but now grows only 10 inches tall. She wonders what can be done to restore its beauty.

It’s difficult to diagnose any plant’s problem by mail, but especially so with a plant such as clematis which can be tricky to grow. Insect and disease problems are not common in clematis, but one cannot rule them out. Unfortunately, one would probably have to dig up the crown and do some serious poking and prodding to discover whether a fungus or insect was damaging either the crown and-or roots. Clematis don’t respond well to such treatment.

Perhaps it would be better to start over with a healthy plant in a different spot following all the guidelines — lime the soil ( 1/2 cup lime, dug in deeply), enrich the soil (manure, sludge or compost, also dug in deeply) and shade the roots. Don’t let the sun strike bear ground where the stem emerges.

A Rockland gardener wants to know sources of plants suitable for bonsai.

The answer to this and virtually any where-to-find-a-plant question can be found in my all-time favorite garden book — “Gardening by Mail,” by Barbara J. Barton (Tusker Press, Sebastopol, Calif.). The book is available at local bookstores and many libraries.

Consulting Barton’s second edition (1987) — the third edition is about twice as thick — I see that bonsai plant sources are numerous indeed. Two that seem especially complete in their offerings are Bonsai Associates Inc., 3000 Chestnut Ave., #106, Baltimore, MD 21217, catalog $2, and Bonsai Creations, 2700 N. 29th Ave., #204, Hollywood, FL 33020, catalog $2.50. Both firms carry, in addition to finished and prefinished bonsai plants, tools, pots, books and supplies for the enthusiast.

Michael Zuck of Bangor is a horticulturist and the NEWS garden columnist. Send inquiries to him at 2106 Essex St., Bangor, Maine 04401.