Basil plant has yellow and brown areas
My basil plant has been in a pot for two years, watered regularly. Right now, it is in part sun outside and was producing great salad clippings, but I fear I am losing it. Leaves have yellow and brown areas. I trimmed it back and lots of new growth was stimulated, but as soon as the leaves start to mature, the same thing happens.
Look under the leaves for gray-pink discoloration/fuzziness. That is downy mildew, which you cannot treat. In that case, use all the healthy foliage you can and throw away the plants. Browning with no leaf-underside fuzziness may be from a root rot associated with overwatering. As weather cools, water evaporates more slowly and plants need less water, because they are not growing as quickly. Watering routines need to adjust for that. Also, if your basil sits in water for a long time after downpours, roots may have drowned. My Annabelle and Niko Blue hydrangeas are quite overgrown. I want to transplant them to give them more space. When is the best time of year to move these hydrangeas?
Fall or early spring (April) are good times to transplant. Fall has the advantage of giving the shrubs three relatively cool moist seasons to get their roots established before they hit a tough Maryland summer. If you choose to transplant now and your soil is extremely dry, compensate by filling the planting holes with water 1-2 times and letting the water soak into surrounding soil. Then transplant and water again. Keep an eye on the weather. Plants like soil about as moist as a wrung-out sponge. Do not let your shrubs go into the winter with dry soil around their roots. The HGIC website’s “Planting Tips for Trees” in the Publications section is helpful. University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos. A Scoliid or blue-winged wasp hunts for grubs this time of year. The insect will dig its way to the grub, paralyze it with a sting and then lay an egg. The larva then overwinters in the grub’s body.
Digging deeper
It’s counterintuitive, but wasps darting and hovering over a lawn this time of year is a very good thing.
Scoliid wasps are hunting for grubs in the soil. First, however, males and females fly in figure-eights for their courtship dance. Once mated, females locate a grub in the soil, swoop down and dig their way to the grub, paralyzing it with a sting and laying an egg on the grub.
After hatching, the wasp larva dines on its fresh food — a gruesome end for the grub—and overwinters in the grub’s body. Full-grown wasps emerge the following August.
Since females lay 1-2 eggs daily for 2-3 months, they make terrific natural grub control.
These unaggressive adults feed on flower nectar, especially goldenrod and horsemint. Look for them there —one half of their bodies gleaming blue-black and the back half a rusty red with two bright yellow “taillights.”