Garden Detective: Caring for a butterfly bush, Japanese red maple tree

It's also common for the leaves of some varieties to turn green during summer and back to red in fall, so maybe a transition was in progress when you wrote. And trees grown from seed are more likely to lose their red color in summer. You say all your trees have the same parent, so if you propagated by seed or pulled up and replanted seedlings, you found growing in the garden, this could be an explanation as well.

Still, it is possible your plants aren't getting enough water, as that's the most common cause of leaves drying up. If that's the case, the advice you were given was correct: Water deeply twice a week with a hose directed at the roots for 30 minutes or more, depending on the force of the water stream.

Sprinkler systems aren't ideal for watering any plants because they don't direct water to the roots, they sprinkle foliage -- which can result in the mold and mildew diseases to which lilacs are especially susceptible -- and would have to be left on for hours to achieve the type of soaking that's required.

I wonder if your plants are located under eaves or if your soil is sandy and draining too quickly. Incorporating compost into the soil and applying mulch will improve moisture retention. If a structure is blocking rainwater from reaching roots, relocate the plant.

There are some diseases that could result in brown leaves, but if affected, the whole plant, not just the foliage, would be in decline.

Meets: 7 p.m. on the second Friday of each month, March through December

Location: Plainview-Old Bethpage Public Library, 999 Old Country Rd., Plainview

Dues: $25 per household

Contact: 516-872-2332, longislandroses.org

Affiliated with the American Rose Society, this club sends members monthly newsletters that include growing tips and information about upcoming meetings, garden tours, garden parties and rose shows. An annual rose show is held every June at Planting Fields Arboretum in Oyster Bay.