Powdery mildew may be the culprit on hydrangea

Q: What is causing the brown spots on all my azaleas? All of these are exposed to full afternoon sunlight.

A: As far as I can tell from your photograph, the plant is a hydrangea species as the edges of the leaves have prominent “toothed” edges to the leaves and not a rhododendron. The condition of the spots and other damaged areas look to be caused by disease — bacteria wilt, leaf spot and powdery mildew. Holes might indicat insect damage.

Powdery mildew can show up with a grayish-white powder on the leaves. In time, it turns purplish brown. It’s a common occurrence when summer ends.

Some of the plant’s condition could be caused by sunburn. This condition could have been more severe this year as the weather suddenly became drier after a very moist spring, which encouraged the powdery mildew to get started. Treatment with a fungicide after a spring rain can slow down and strop the disease. Each heavy rain will wash off the fungicide and it must be reapplied.

Q: I have a large bed of lily of the valley. Some of the leaves are dying back; some are still green. Should I cut down all the foliage for winter?

A. Lily of the valley (Convallaria majalis) will lose some leaves in late summer because of hot weather. If the plants look poorly, you can trim the leaves off with a lawn mower on a high setting to force the plants into an early dormancy. These plants grow best in the shade or on the north side of a structure. Once they get started, it can be difficult to keep them in bounds.

This time of the year or in early spring is a great time to divide the “pips.” You can dig them up and thin out plants because over time they become too crowded. The roots will be light yellowish brown and support a distinctive bud. These fat buds will produce flowers in the spring. If the buds have small buds they will produce just leaves the first two years until the plants can store enough energy to support flowers.

Do not baby these plants. The harsher the winter the better for these plants grow and produce flowers. The largest and more numerous lily of the valley flowers I have ever seen where growing in Canada

You can even keep some of the larger pips in a freezer wrapped in sphagnum or peat moss. When you wish to start them, allow them to thaw and place the pips in a bowl with porous potting mix. Keep them at 55 to 60 degrees at night and about 10 degrees cooler during the day. The pips then form leaves and finally the flower spikes will follow and you will experience the most fragrant scent when the blooms are fully mature.

These are preferred flowers for bridal bouquets. They have a high price which have a large price due to their demand especially in June when they have to be forced into bloom as described above. In nature, the flowers bloom in early May.

This story was originally published October 1, 2015 at 3:32 AM with the headline "Powdery mildew may be the culprit on hydrangea."