Q Last year we bought some Picotee petunias (Red Picotee and Blue Frost) from a garden store and had a fantastic show around our steps. This year we would like to start seeds and grow them ourselves. How soon should seeds be started? C. S. Williamsport, Pa.
You should allow about 12 weeks from seed sowing to planting-out time, if soil temperature is kept at 70 to 72 degrees F. day and night.
Use one of the artificial mixes, and keep it moist at all times. We do not cover petunia seeds with medium, but press sown seeds into soil by rolling an empty glass jar over it. When adding water to the subirrigation pan, be sure it is tepid to the touch. Q I have bought a fluorescent light (especially for growing plants) which is fastened to adjustable legs. I want to grow some geraniums from seeds and wonder if fluorescent lights will give off enough heat to help the seeds germinate properly. How long will it take for the seedlings to bloom? A. K. F. Hicksville, N.Y.
Fluorescent lights do not give off enough heat to keep soil temperature at the proper level for germination. We suggest you buy a heating cable to use under your seedbed. A soil temperature of 72 to 75 degrees F. (22 to 24 degrees C.) must be maintained constantly until seeds germinate.
Seeds usually sprout within five days and will produce budded plants within 14 to 18 weeks. Use one of the artificial soil mixes and keep moist. Garden stores and many garden catalogs now sell heating cables, growing media, and fluorescent-light setups for amateur gardeners.
If you send a self-addressed, stamped envelope, we can send instructions on the use of heating cables. Q My mother and I have decided we would like to grow some flowers which could be made into dried bouquets that we could sell in late summer and fall. Would you suggest some that would be colorful and not too difficult for beginners to grow? G. H. Findlay, Ohio
Many seed catalogs have special sections listing ``Everlastings.'' Three annuals which we grow each year are strawflowers (Helichrysum), Statice sinuata, and Gomphrena. Others we like are Ammobium, Sunrays (Acroclinium), and Love-in-a-mist (Nigella). We recommend two perennials, easily started from seeds: blue salvia (S. farinacea) and Chinese lantern (Physalis). The biennial money plant (Lunaria) is also worthy of a permanent spot in your planting. Don't overlook ornamental grasses for feathery beauty. Q As a boy I often helped my grandfather take cuttings of many plants which he rooted and shared with others. When he planted rose cuttings, he put a small slit in the end of each cutting and inserted an oat. His assertion was that it made the cuttings root faster. Is there any truth to this theory? F. B. Texarkana, Texas
There is increasing evidence that a few grains of wheat or oats planted around a cutting or one inserted in a slit in the end will stimulate rooting. It is noted that either hormones or some other stimuli from the newly formed seedling roots cause the cutting to root faster.
We have observed that cuttings root better when they are put in a glass of water that has had willow twigs soaking in it for 24 to 48 hours (a tip passed along by Prof. Makota Kawase of Ohio Agricultural Research at Wooster, Ohio). We find that cuttings of many houseplants root faster if they are placed in jars of water containing rooted coleus cuttings. Q A couple of years ago we read a recipe for making a homemade cut-flower preservative. It was: 4 teaspoons of sugar, 2 tablespoons of white vinegar, and 1 quart of water. I had not used it until this Christmas when we received a large bouquet of mixed flowers and there was no packet of preservative with the bouquet. To my dismay, some small chrysanthemums wilted soon after. The other flowers did not appear to be affected. I'm sure all were fresh. How could this have happened? M. B. Marietta, Ga.
We used to recommend white vinegar, but no longer. Instead, try 2 tablespoons of fresh lemon juice, 1 tablespoon of cane sugar, and teaspoon of household bleach in 1 quart of water. Remove all leaves that would be under water. Researchers have found that white vinegar has varying amounts of acid and when the acid content is too strong some flowers are affected adversely. Acid content can vary even within the same brand. Q Many months ago you had instructions for growing a pineapple from the top of one. We've had great success getting the pineapple to grow into a fine specimen, but we lost the instructions which told how to force it to flower. It is now about three months short of two years old. Could you plase tell us how to get it to flower? Mr. and Mrs. R. C. Kansas City, Kan.
An apple, because it gives off ethylene gas, will do the trick. Place the pineapple plant in a large clear plastic bag (pot and all). Put the apple in the bag with the plant and tie the bag shut, then move the plant to more subdued light for three days. After this time, remove the bag and place plant back in its sunny spot. About two months later you should have a bright red, cone-shaped structure from which flowers develop.
FREE: Anyone wanting complete instructions on how to root a pineapple top, get it to grow and flower and produce fruit, may obtain a leaflet by sending a self-addressed, stamped envelope to Ask the Gardeners.
If you have a question about your garden, inside or out, send it to the Garden Page, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115. Doc and Katy Abraham are nationally known horticulturists.