Lichen on a lilac, searching for purple lilacs

Q: I have an old lilac bush that looks OK, but its trunk and branches are coated with a yellow moss that doesn't brush off easily. Will this hurt the lilac? How can I get it off?

A: It's most likely a harmless lichen growing on your lilac, and it's a sign you live where the air is clean. Lichen are considered a sign of good ecological balance, so enjoy how the yellow lichen brightens up the branches of your lilac.

Q: Where can I find a dark-purple lilac? I've seen old ones in gardens around town, but the nurseries seem to carry mostly white and lavender lilacs.

A: There are a number of dark purple, very fragrant lilacs that are worth searching for, including Monge, which is a single flowering, heavily scented lilac, and Adelaide Dunbar, with double purple flowers. Perhaps the best known, deepest-purple lilac is My Favorite, hybridized by Hulda Klager in Woodland (Cowlitz County) nearly a century ago.

You can ask for these at area nurseries, or use your quest for dark-purple lilacs as an excuse to visit the Hulda Klager Lilac Gardens, open to the public and located at 115 S. Pekin Road, Woodland, about 30 minutes north of Portland. Their 2008 Lilac Festival runs through Sunday; see the Hulda Klager Web page (www.lilacgardens.com) for details and directions, as well as color photos of the lilacs they offer for sale.

Q: It seems like I always hear about garden tours after they happen. Can you tell me when the big ones are this year and recommend which are worth attending?

A: The Northwest is lucky to have so many gardeners willing to open up their gates for good causes. It's difficult to recommend the best tours, because every year offers a palette of different gardens, but here are a few that are always special:

PlantAmnesty's walking tour of Belltown Gardens, which is as urban a garden tour as you can find, noon-3 p.m. May 18. For more information, call 206-783-9813 or e-mail info@plantamnesty.org.

Whidbey Island Garden Tour, 10 a.m.-4 p.m. June 21. For garden descriptions and tickets, $20 for adults and $10 for children 2-12, see www.wigt.org.