Ask the gardening expert

Here in the Northwest tomatoes ripen later than in other parts of the country. I have lots of green tomatoes and wonder how I could ripen them? Should I start clipping blossoms? I’ve heard that “stressing” the plants by reducing water and fertilizer can force ripening. I also heard I should strip the leaves to expose the fruit and hasten ripening. Can you advise?

In cool summer seasons such as we experience in the Pacific Northwest, it’s important to choose cool-season, disease-resistant varieties and then provide them the ultimate growing conditions. Some gardeners use black plastic mulch to help keep the roots warm and plant in the sunniest spot available. Many cover tomato cages with clear plastic early in the season to help the plants reach maturity a few weeks earlier. I’ve heard that if you remove late-season blossoms, plants will redirect energy into ripening remaining fruits. I’ve heard that withholding water will stress the plants into ripening fruit (since the last thing a plant does before it dies is to set seed), but I think the stress might also affect the quality and flavor of the fruit.

I wouldn’t remove too many leaves to expose the fruits to more sunshine, because you might end up with sunburned tomatoes. I do know that warm weather, especially warm nights, will have more effect on ripening than exposing the fruits to direct sunshine. Additional fertilizer will encourage additional growth, at the expense of the existing green fruit, so don’t do that.

Make sure the vine stays dry, and that muddy soil does not splash up on the plant, allowing diseases to get started. For the best possible performance next year, start tomato plants indoors, then put them out in the garden when overnight temperatures are consistently 50 degrees.

Is fall a good time to divide and replant perennials like sedum? Or is it best to do it in the early spring?

Fall or spring are good times to dig and divide them. If you do it in the fall, the plants will establish themselves before the spring growth spurt. If you dig and divide in the spring, the plants will be ready to grow so they will establish quickly and put out top growth.

I planted 4-four-foot tall hollies last year. In early spring they looked great — they even had berries. But last winter, and even now near the bottom of several of the plants, leaves are turning yellowish and falling off. All of the bushes have berries, but I’m worried about them. Should I apply a fertilizer?

Most likely they’re fine. Pay particular attention to the new growth. If new growth is healthy and vigorous, my guess is the plants are fine. Don’t worry about them unless the new growth is weak or unhealthy looking. It’s not unusual for lower leaves of shrubs to yellow and fall off.

Do not fertilize now. Keep all new plants well watered. Until their roots are deeply established in the surrounding soil, they can suffer drought easily in this dry fall. A 1- to 2-inch-deep mulch also helps maintain soil moisture and prevent weeds.

Celeste Lindsay is a WSU-certified master gardener. Send questions to mslindsay8@gmail.com.