Q: Several years ago I bought a Ceanothus griseus horizontalis, and it was marked "protect in winter. " I live outside Redmond, and I've kept it in a pot close to the house the...

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Q: Several years ago I bought a Ceanothus griseus horizontalis, and it was marked “protect in winter.” I live outside Redmond, and I’ve kept it in a pot close to the house the past few years. I’ve been unable to find any information on it. Can you help?

A: Your plant’s common name is California lilac, which tells you it is native to warmer climates. It has been my experience that Ceanothus die far more often from drowning in wet soil than from cold temperatures, for they require perfect drainage. A raised bed or slope is best, particularly one facing west or south, as they love sun and as much heat as you can give them. Your low-growing, blue-blooming C. griseus horizontalis is officially a zone 8 plant, but if you find a microclimate that suits, it should do fine unless we have a particularly cold winter. (I hate to even write that, because it sounds like I’m tempting an early arctic blast).

Q: Is there a way to force tomatoes to ripen on the vine?

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A: It’s time to obsess over tomatoes. Thanks to the long, hot summer, the tomatoes have actually ripened this year. I sought the expert advice of Wally Prestbo, aka Mr. Tomato, who grows 24 varieties of tomatoes for the Master Gardener Demonstration Garden. This guy knows his tomato tricks. Like a true and humbled gardener, Prestbo points out that we’re all at the mercy of Mother Nature and weather patterns, and tomatoes require continuous heat in order to ripen.

But there are a couple of techniques to nudge nature along. As autumn approaches, Prestbo stops watering his tomatoes as frequently or as copiously as during the summer. This stresses the plants and encourages the fruit to ripen faster. He also removes all blossoms, so that the plant’s energy goes into ripening the fruit already on the vine rather than to produce new fruit.

If you’re worried about the temperatures dipping too low at night, you can pick tomatoes that have started to color up and bring them indoors, because at this stage it is warmth more than light that ripens them. Prestbo suggests sticking tomatoes in a paper bag with an apple or banana, both of which give off gases that speed ripening. This is also a good way to rescue nearly ripe tomatoes from late blight, which is Prestbo’s concern this time of year, for it usually hits as soon as the cool rains come in autumn.

The good news is that most years the only tomatoes we have are the ones we ripen indoors — at least this summer produced a bumper crop.

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.