QUESTION: My birch tree has become host to a fast-growing perennial vine. It has large leaves like grape leaves and hard, pea-size fruits that are pale purple with speckles, or blue, depending on age. What is it?

ANSWER: You have not used the word "beautiful" but other than that have written a standard description of porcelain berry, Ampelopsis brevipedunculata. It is a member of the grape family, and a textbook example of an invasive ornamental.

It thrives in a wide range of soils and climates, it is seldom bothered by disease and it is lovely, especially in fall. The clusters of berries start out green, then ripen through yellow and lilac until they shine purple blue through autumn-colored leaves.

Berries remain on the plant until they are eaten by birds, and you know the rest of the story: A native of Northeast Asia that looked great when it was introduced (in the 1870s) now looks like a big problem.

Porcelain berry spreads most aggressively near water, in disturbed areas like roadsides or cleared forest. In mild climates, it swiftly produces choking root systems and smothering blankets of greenery.

The only herbicides that can stop it are likely to stop the birch as well, but you can starve it out. Just keep cutting off the new growth until it gives up. Do not try to pull out the roots. You will not get them all, and those that remain will simply send up new plants.

QUESTION: The flower stalks of my reblooming day lilies, Stella D'oro and Happy Returns, die quickly, although the leaves remain attractive and the plants do flower again. Can I prevent this?ANSWER: It is normal (and inevitable), especially with rebloomers. Your plants are varieties that usually flower in late spring, stop briefly, then flower again and again as summer turns to fall. Flowers and plants are on the small side, both have yellow blooms, and although there are many flower stalks, they do not all carry large numbers of buds.This leads to a lot of time-consuming tidying. Removing spent flower stems is not just a matter of aesthetics. Cleaning up discourages disease and encourages more blooms.To have flowers all summer without endless dead-stalk patrol, consider planting some more recent varieties. The latest offerings have substantial flowers in unusual shapes and colors, and they tend to have a high bud count per stalk, so there is less cleanup involved.Sources for wide selections of modern reblooming day lilies include Oakes Daylilies, 800-532-9545 or online at www.oakesdaylilies.com, and Homestead Farms, 888-314-3148 or online at www.homesteadfarms.com.Address questions to Garden Q&A, The New York Times, 229 W. 43rd St., New York, NY 10036, or by e-mail to gardening@nytimes.com. Those of general interest will be published.