QUESTION: My hydrangea is turning out not as blue this summer as I'd like. What is the stuff you put on a hydrangea to make it bluer?ANSWER: Aluminum sulfate is sold by the bag in garden centers, hardware stores and home centers for this very purpose. The presence of lime in the soil, often from adding it to the lawn or flowerbed, raises the pH and makes the hydrangeas less likely to take up aluminum.By adding aluminum sulfate to the soil, you will lower the pH, and increase the uptake of aluminum, thus making the flowers of mophead hydrangeas (not the naturally white ones) blue.You don't usually have to do this to young plants because growers treat the soil to encourage the pink or blue they wish to develop. But as time passes after the shrub is set out in the ground the effect wears off. In neutral or alkaline soil, these hydrangeas produce pink flowers.One good rule is to dissolve one tablespoon of aluminum sulfate in a gallon of water and drench the soil around the plant in March, April and May.Remember, this is not fertilizer. The plants will still benefit from an acid-based fertilizer.

QUESTION: Last fall I bought a variegated redbud. It was just a stick and some branches with much promise. I planted it around Thanksgiving and gave the roots starter fertilizer as was suggested. It had some nice blooms this spring and now it is glorious, with fluttery cream and green leaves. Alas, the leaves now have brown edges and the branches droop. I think the droopy branches might be characteristic, but not the brown edges.ANSWER: What was the condition of that tree's roots when you got it home and in the ground? Even with starter fertilizer, the tree may still be racing to catch up on the loss of roots.What you describe sounds like leaf desiccation due to inadequate water uptake. And that is due to inadequate roots. As long as the branches don't die, it should be OK if you keep the tree watered through the summer, when the stress will really be on it.

QUESTION: My neighbors disagree about whether rose bushes should be planted with the top of the root ball even with the ground or planted on small mounds, surrounded by a watering trench. I've never heard of the latter, but then I've never lived in this region, either.ANSWER: The special thing about planting roses in the Piedmont is that the bud union should be just above the soil line, about 1 to 2 inches. The bud union is the knobby growth at the base of the plant where the rose was grafted onto rootstock. By positioning this bud union above the soil, you encourage the development of more rose canes.Perhaps the soil mounds under discussion are the ones created in the planting hole before a bare-root rose is set into it. This mound should be cone shaped, made of good soil liberally laced with organic matter, and the roots placed around the cone. Then the hole is filled to the top. Make sure the plant does not dry out as the canes put out new growth. Water every couple of days.Any boxed or potted rose in the stores now is likely to show growth already. It should take off well once the roots get in the ground. Just set a potted rose into the planting hole, disturb the roots as little as possible and fill the hole with good organic soil.As for watering, the most important thing to remember is to avoid - as much as possible - wetting the leaves, which encourages rose diseases. This can be accomplished with soaker hoses running among the roses, under the mulch.

QUESTION: I bought daylilies that had this aggravating Liriope spicata mixed in. I dug the bed out completely two years ago to get rid of this weed and replanted my daylilies. This year, the liriope is back, overwhelming my daylilies and appearing in other beds and in my lawn. Now there is too much of it for me to dig up. Do you have any suggestions?ANSWER: I suggest a paint job. And it will be tedious. What a scene: Daylilies rising. Liriope creeping. Gardener really irritated. Get a paintbrush and dip it into a bottle of herbicide such as RoundUp. Paint the leaves of the creeping liriope, but don't get the herbicide on the daylilies. Actually, I think this job will be worse than tedious, especially if all the plants are close together. The daylily leaves are much taller than the creeping liriope, so you are going to have to work between them, brush and bottle in hand. No easy task. I hope the liriope is reachable without stepping on the daylilies. Wait until almost all of the blooms are gone. Of course, by then it will be hot as July.

Plant a centerpiece that will be ready for your picnic July 4.An 8-inch pot is a good size for a table that seats six or eight people. If your table is longer, make two pots. Finding blooming flowers in America's colors isn't hard; garden centers are full of them, and most combine beautifully and naturally.The key is getting bright red, true blue and sparkling white. Look at petunias , scaveola, bacopa, angelonia, salvia, verbena, sweet alyssum and million bells.Put the taller ones in the center, the mounding ones and trailing ones around the perimeter. Keep the pot in a sunny spot and water well so the flowers will be in perfect condition on July 4.Send your gardening questions to Nancy Brachey, The Charlotte Observer, P.O. Box 30308, Charlotte, N.C. 28230.By KRT News Service