What to do this week Use overhead sprinklers to water early in the morning so leaves have time to dry before higher humidity promotes fungus growth. This also reduces slug damage to hosta leaves. You can also use a soaker hose or drip irrigation so the roots are watered but foliage stays dry. Plant seeds of spinach now to harvest in fall. Pick summer squash and zucchini before the fruit reaches 6 inches. Trim off green tops before harvesting carrots to avoid losing moisture.
Q. I have three older yews in front of my house and wonder whether, as they grow older, the outside green area will become less pronounced, showing more of the inner wood. I trim them every fall for the winter months and notice that what seems to be a dead interior of the bushes becoming more prominent. If I trim them back too much, they don’t look appealing because they seem to grow just from the outside. Just how long do yews last before they need to be cut down? Is there another way to keep them looking lush for years to come?
KEN WESTHASSEL, MEDFORD
A. Yews can live a long time, but you need to prune them correctly. And I mean prune, not trim. Don’t shear the outside of the shrub like you are trimming a moustache. Leave the surface of the shrub alone. Instead, take a long-handled pruner, reach inside, and cut some of the longest branches back to where they connect to another branch in the interior of the shrub. Pruning cuts made in the center of the shrub will stimulate latent buds to break, which are essential to the renewal process. But never leave a stub of a branch like an amputation. Make the cut flush with the joint of another branch it is attached to. And don’t prune in the fall. I don’t think it prevents winter moths, but it might stimulate vulnerable new growth that gets killed by winter cold before it “hardens off.” You can prune in deep winter and in early summer, but the best time is spring.
Q. For the past three years, my long-established pachysandra has been steadily shriveling up and dying. What starts off as a small brown spot becomes larger and larger as the plant withers away. I have tried transplanting healthy pachysandra and vinca into the brown areas, but they eventually die as well. Always enjoy reading your tips in the Globe!
PHOEBE FRANCIS, LINCOLN
A. Volutella blight, also called leaf and stem blight, is the most destructive disease of pachysandra and is caused by a fungus. Leaves develop irregular tan-to-brown blotches that increase until the entire leaf turns brown and dies. Plants often die in patches. Mowing and then vigorously raking the bed can help get rid of infected plant material. But this blight is usually a problem only when the plants are already stressed. Are you trying to grow them (or anything) under a Norway maple? You can spray this blight with Bacillus subtilis, QST 713 (trade name Serenade), an organic biological option, when new growth starts in the spring. But I would start by top-dressing with compost and then inter-planting an alternative ground cover, such as a Vinca minor (periwinkle) or Geranium macrorrhizum (bigfoot geranium) — and watering deeply once a week in the summer.