Q: Now that most of the roses and perennials are finished, my garden looks plain green. I don't have much room, but I would like to add...

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Q: Now that most of the roses and perennials are finished, my garden looks plain green. I don’t have much room, but I would like to add a few plants to my front yard for fall color. I have one Japanese maple that is pretty — could you give me a couple more suggestions?

A: You can pack in a lot of autumn color if you plant in layers. It’s like fall fashion, but instead of leggings and jackets, you’re dealing with perennials and shrubs. By layering shades of gold, orange, rust and plum from ground covers to small trees, you’ll get maximum effect in minimal space.

Since individual plants within a species vary widely in their fall coloration, you’ll want to select plants within the next couple of weeks, when they’re in their full autumn glory.

At ground level, plant dwarf plumbago (Ceratostigma plumbaginoides), a deciduous ground cover. As the weather cools, its foliage turns to shades of crimson and purple, showing off the little gentian blue flowers.

One of the taller sedums that colors up in autumn, such as Sedum ‘Matrona’ or Sedum ‘Autumn Joy,’ would be a second layer for color until frost.

Few shrubs are flashier in autumn, and easier to grow, than the oak leaf hydrangea (H. quercifolia), with creamy towers of fading flowers set off by bright fall foliage.

Then for the tallest layer, choose one of the many small trees that turn to flame as the days grow shorter. Slow-growing sourwood (Oxydendrum arboreum) is one of my favorites, for it drips elegantly pale flowers against vivid red leaves. Multi-trunked, petite trees like vine maples (Acer circinatum) and Amelanchier x grandiflora ‘Princess Diana’ are also good choices for the smaller garden.

Q: I can’t choose between all the asters in the nursery right now. Which are best?

A: It depends on what colors and shapes you prefer. My own favorite is the dependable old Aster x frikartii ‘Monch,’ because its pale purple, yellow-centered, daisylike flowers bloom for nearly six weeks and are lovely in autumn flower arrangements.

And even though it flops if you forget to pinch it back in early July, I love the New England Aster ‘Alma Potschke’ for its vibrant flowers. Its bristly, watermelon-colored flowers are such a surprise and so effective in the autumn garden.

Also consider the starlike wood aster (Aster divaricatus) that foams up along the ground with wiry foliage and tiny dots of flowers.

Q: After two hip replacements and having passed 65, my gardening is limited to a few large planters and two hanging baskets.

After I started to garden in large planters, each spring I would just about totally replace the soil, mixing in a lot of compost, fertilizer and some really good potting soil with the dirt that was left. I’m wondering whether there are some things I can do to preserve whatever is in the good dirt left in the planters over winter. I want to continue to do my own gardening for as long as I can.

A: Soil in large containers does need to be refreshed in the spring, but not necessarily replaced. If you mulch with a thick layer of compost in autumn, that’ll help preserve nutrients through the winter. Then in early spring, just dig in some compost and manure or feeding mulch (well-composted bark and manure) to fluff up and enrich the soil, mulch again and your plants should thrive.

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.