When is the best time to cut back hydrangeas?

I have three nice plants that have bloomed beautifully and then showed fall colors. At the same time, when the blooms changed color, they started showing new buds all up and down the stems.

Over the winter, the old leaves seemed to die slowly. So should I cut them off or wait for them to fall off? One plant had fresh-looking leaves into November.

– Jean Stiarwalt, Rocklin

According to UC Master Gardener Bill Pierce, the best time to prune hydrangeas is in late summer, after the blooms of big-leaf hydrangea (Hydrangea macrophylla) have faded.

Branches that bore flowers should be cut to within a foot of the ground or cut back so that only two to four buds remain on the branch.

This is done in the hope that some of these buds will grow into branches before the plant goes dormant. And, since these kinds of hydrangeas flower on wood that grew in the previous year, there is thus potential for more flowers the next year.

Many gardeners prune hydrangeas a second time in January because, while the plants are out of leaf, it is easier to identify and eliminate crossing branches and old wood. Removing old wood makes more room for new branches to sprout from the crown of the plant.

My husband and I took our grandkids to the park late last summer. We parked near an oak tree. Our picnic table was also under an oak tree.

We noticed hundreds of tiny round objects, both on the ground by the car and on the table. They were very similar to the small wood pellets left by termites.

The only difference was that they were moving! If they had been larger, they would have looked like Mexican jumping beans.

Our grandson said he had a friend who knew about science and that he said there were little worms inside the little round balls.

We also noticed that our car windshield had sticky little drops on it that hadn't been there before we parked under the oak tree.

Can you give us a clue to this phenomenon? Are these dangerous? They are small enough to be accidentally inhaled or swallowed. Are there really worms inside? – Patricia Opfer, Elk Grove

What you experienced were the larvae of oak gall wasps, says UC Master Gardener Bill Pierce.

The size, shape and color of galls vary greatly depending on the species of wasp and the part of the host plant where the egg is laid. Some variations: off-white pingpong-like balls, starlike formations that grow on the underside of oak leaves or swollen growths on small oak branches. All are common in our area. The wasps and their larvae are harmless to both man and plant.

The sticky material on the car was probably honeydew produced by aphids or scale insects in the trees. These insects suck plant juices; ants frequent the site to rob some of the sugars that these insects are harvesting and the surplus tends to drip down on anything that is below.

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