What to do this week When watering, make sure your most valued trees and shrubs receive at least an inch a week over their root zones to help them survive. Summer drought can kill even large trees, though often the effects develop later. If red lily beetles are despoiling your lovely lilies, hold a jar of soapy water underneath and give them a shake or a prod. They drop like a stone and drown. It is satisfying at first. But when it gets monotonous, plant some “Black Beauty’’ heirloom lilies, the only variety I know that’s distasteful to these beetles. You can order these bulbs now for fall planting (www.vanengelen.com) along with your tulips and daffodils.
Q. The tops of my roses died back. I get that. But why do I also have gladiola and dahlias blooming now that I planted last year? They’re not supposed to be hardy here. Does this mean I don’t have to dig up my dahlia tubers and bring them indoors?
J.K., Lakeville
A. The climate is not just changing; it’s also becoming more unpredictable. So we had a very warm winter except for two nights in March when temperatures plunged far below zero. This killed the tops of many roses and other shrubs, but the roots survived. They were insulated by soil, so most of these plants have resprouted. The big surprise, this was also the first year that dahlia bulbs that spent the winter outdoors sprouted and bloomed without dying from cold. How could that be? Those two cold nights did not last long enough to freeze the soil, apparently. So it was a cold winter for rose bushes, but a warm winter for dahlia bulbs planted under a snug blanket of earth. This might tempt you and me both to leave tender bulbs in the ground this fall. Gardening always involves experimentation, and why do more work than you have to? But I’m digging up my favorites and bringing them indoors just to be safe.
Q. Why won’t my hydrangeas bloom? I live in Zone 5 and have a few said to be appropriate for this zone, but they don’t bloom.
KATE ULLMAN, Jamaica, Vt.
A. The buds formed the previous fall and were probably killed by two nights of super low temperatures. To ensure your hydrangeas bloom next year, try this: Wrap chicken wire around the perimeter of each shrub and fill it with oak leaves, covering the entire bush and all its flowerbuds. Oak leaves stay lofty and don’t mat down as quickly as other types of leaves. Bust your hydrangea out of jail at the end of March. Or you could just buy one of the new type of hydrangeas that bloom on buds formed after winter is over. They come in many colors but the blue-flowered “Endless Summer’’ is the best known. There are many species of hydrangeas. Most with white flowers are more cold hardy and trouble-free than the colored ones, especially in the north. Encourage new growth and more flowers by cutting one-third of the stems back to the ground during the winter.
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