Hydrangea colors

This mop-head hydrangea exhibits the traditional blue color. Bloom colors are determined by a variety of factors, including age of the plants and soil acidity. (KIM KIM FOSTER-TOBIN / THE (SOUTH CAROLINA) STATE, 2003)

Q: What kind of hydrangeas have big, round flowers? Are they always blue?

A: Hydrangea macrophylla, known as mop-head hydrangeas, blossom in shades of purple, white, mauve, burgundy and pink, as well as blue, and the flowers change colors as they mature. Some hydrangeas have fairly fixed flower color, while the flowers on others vary between pink or blue depending on the acidity of the soil they grow in.

Q: I know it is possible to prune any plant at any time, but I was wondering if I'd do more harm than good by cutting back my large, 40-year-old flowering cherry tree. If I won't ruin the tree, when and how much should I prune it?

A: Ornamental cherries don't take well to pruning, so be very cautious in cutting back a tree that's a feature in your front garden. When pruned, they tend to erupt with water-sprouts, those skinny straight-up branches that disfigure the tree's shape. Cherries also die back easily after being clipped, so resist the temptation to prune back the limbs, or you'll soon be looking at a whole lot of dead wood.

If you do decide to prune, use a light hand. Master pruner Cass Turnbull says that 90 percent of your cuts on ornamental cherries should be dead branches, dead stubs and dead twigs.

Take out the very worst, and leave the rest alone for the sake of the overall health of your tree. And don't get so carried away that you prune off the little twiglets along the trunks and branches, because they bloom in the spring.

Q: Could you please recommend a book on caring for roses in Washington?

A: It's a very good idea to seek out advice on growing roses specific to our rose-challenged climate. One of the best sources of information is the Seattle Rose Society Web page, www.seattlerosesociety.org. Click on "rose care" to find reliable information from dedicated local rosarians.

For a realistic look at which roses do best in our climate and in specific garden situations, take a look at the rose chapter in "The Pacific Northwest Gardener's Book of Lists," by Ray and Jan McNeilan. It's available in public libraries, and at the Elisabeth C. Miller Library at the University of Washington Botanic Gardens.

Good rose care starts with selecting the right plants. A few of the roses highly recommended for Western Washington include Rosa glauca, a shrub rose with pewter-colored foliage; rugosa roses such as the highly fragrant 'Blanc Double de Coubert' and the compact 'Purple Pavement'; and shrub roses such as 'Sally Holmes,' 'Bonica' and 'Mutabilis.'

Valerie Easton also writes about Plant Life in Sunday's Pacific Northwest Magazine. Write to her at P.O. Box 70, Seattle, WA 98111 or e-mail planttalk@seattletimes.com with your questions. Sorry, no personal replies.