Q - Last year my Burford Chinese holly was loaded with berries, and this year there are none. It appears to be healthy.
A - Many kinds of plants, including Chinese holly, skip a year when they bear particularly heavy crops. That's because they're exhausted by producing the heavy crop and there's not enough energy (stored food) for flowers and berries the next year.
Some apple trees that are alternate bearers can be made to bear every year by removing a lot of the small fruit early in the season to reduce the load. It's a good idea to thin the fruit anyway, because that remaining will be larger and of better quality.
Q - This year I raised some impatiens plants from seed. One plant has grown some 40 inches tall, the largest I've ever seen, and it blooms constantly. I've saved some seed from it for planting next spring. Am I likely to get the same-size plant?
A - Reports of such unusual plants are received frequently. They result from seed not true to type getting into the mixture, which sometimes is almost inevitable. If you plant seed from it, heaven only knows what will result. It could be interesting to see. But the tall plant is no novelty to the hybridizer - he's seen thousands of them in trying to create the kinds he wanted.
Q - I have six hydrangeas along the side of my house and quite a lot of shade. Three grew tall but had almost no flowers, while the smaller ones, in more sun, had flowers but very little foliage. Should they be pruned, and if so how far back?
A - Hydrangea hortensis (bears pink or blue flowers) should be pruned immediately after blooming, usually early August in this area. Cut back enough so that only two sets of leaves remain on the stem. If the canes are crowded, remove some of the weaker ones. If pruned in late fall, winter or spring, the stems that were cut will not produce flowers the following summer.
Hydrangea hills-of-snow (white flowers) blooms on this year's growth and should be pruned in early spring. It usually benefits by heavy pruning and usually blooms even if cut back to the ground. The quality of the flowers depends on the vigor of the plant. There will be few if any flowers in heavy shade. Fertilizing in early spring and watering during dry weather will result in more and better blooms.
Q - My bearded iris has become quite crowded. When's the best time to divide it?
A - Bearded iris usually needs to be divided every four or five years. Japanese and Siberian iris don't require frequent division. Clumps of Siberian iris should stay in good condition for a dozen years or more. The best time to divide bearded iris is soon after it finishes blooming, when its dormant period begins. It continues for several weeks and then new root growth develops.