Q&A.

Q. Quite some time ago you mentioned something that could be mixed with leftover seeds to keep them better in storage. Perhaps there are others who would like to know how to store seeds (either left over or gathered from their own plants).

Seeds, if gathered from one's own plants, should be thoroughly dried by laying them on a plate in a dry, airy place for a week or so. To keep gathered or leftover seeds, store them in a glass jar with a tight lid.

Before putting them in the jar, add some dry milk that has been wrapped in a paper tissue. To wrap, lay two or three thicknesses of facial tissue on a flat surface and pour onto the center an amount of dry milk approximately equal to the volume of seeds. (It usually averages 2 tablespoons per quart jar of seed packets.)

Fold the side over and fasten with tape or a rubber band. Place the packet of dry milk and then the seeds in a jar. Tighten the lid. Store at no higher than 50 degrees F. for best results. The temperature can go as low as 34 degrees F.

Q. A verse of a little poem is going through my mind, and it might be known to you folks since you're so tuned to plants and nature. The first verse is: ''Who can mark the moment/when summer turns to fall?/ Who can find the corner/in the long, green hall?'' Can you help out?

We do know this delightful poem because we read it every fall on our radio program (giving credit, of course). We clipped it from The Christian Science Monitor several years ago.

The name of the poem is ''Who?'' by Ruby Zagoren. The rest of it is as follows: ''Who sets the clock for growing/of goldenrod and tansy;/the same alarm that halts/the hollyhock and pansy?/Not we of finite talent,/not we of human sight,/but He who measures heaven/with yardstick of the night.''

Q. We had an elegant array of double French marigolds this past summer, but the frost finally got them. We also had one called Dainty Marietta, a single, that gave us pert little bouquets for our friends. Is it possible to plant seeds now and have them bloom in our south window this winter?

Marigolds make a lovely indoor plant if they get plenty of light and some sun each day - which you should get in a south window. Besides the doubles, another single you might try is Naughty Marietta, one of the parents of Dainty Marietta, which grows just a bit taller.

Sow the seeds directly in pots in a peat-lite mix, which is available at garden stores. Cover lightly and keep moist. You should have blooms in about 10 weeks.

Q. When I was a child in North Carolina we had a persimmon tree, but the fruit was very puckery. While in Texas last fall I had some large golden persimmons (rather flattened on both ends), which had a superb taste. Would you know the name and tell me if I could grow it in Virginia? I was told it was a Japanese variety.

The golden one with flat ends with which we are familiar is kaki. The variety fuyu or fuyugaki is often listed in nursery catalogs. It is self-fertile and hardy in USDA zones 7 to 9, which would allow them to have temperatures above 60 degrees F. for the ripening period in October-November. This, of course, would include your area in Virginia.

Kaki is actually indigenous to China but also grown much in Japan. As a result, it is thought of as a Japanese species. If you can't locate it under persimmon in an index, try to find it under Diospyros, its scientific name.

Q. A friend told me I could change the color of hydrangeas by adding aluminum sulphate to the soil for blue or lime for pink. I changed the blue ones, which are growing in front of our house, to pink by sprinkling lime around the bushes. I have tried to change the white one to pink or blue, but it doesn'trespond. Does it need some other treatment? The variety is called Snowball bush.

White varieties of hydrangea will not change their color no matter what treatment you give them. There is an oak leaf hydrangea that opens pure white but then gradually turns pinkish. On the other hand, Hydrangea arborescens (Snowball or Hills of Snow or Annabelle) remains pure white.

Blue varieties need an acid soil. The blue color can be induced by adding about 1 tablespoon of aluminum sulphate per bush. Pink requires a neutral or alkaline soil, and you did the trick by adding lime until a soil test would show you had a pH of 7 or 7.2 on the pH scale.

Q. As I watched squirrels burying acorns from our large oak tree, the thought occurred that some varieties of acorns might be edible for humans. I tasted a few and they were slightly bitter but not altogether unpalatable. Do you know of any species that would be more tasty?

Ken Asmus, writing in NAFEX (North American Fruit Explorers) Quarterly (Summer 1984), says he has found that chinquapin (Quercus muhlenberg) and Burr oak (Q. macrocarpa) produce some sweet acorns; Burr at the rate of about 1 in 10 . He asks folks who have found, or would like to find, sweet or tangy acorns to write to him at 721 Fletcher, Kalamazoo, Mich. 49007. To find out more about NAFEX, write to Mary Kurle, 10 S 055 Madison Street, Hinsdale, Ill. 60521.

When writing to either, enclose a stamped, self-addressed envelope.