With the start of October, gardeners who for months lusted (often obsessively) after flowers and vegetables turn their considerable focus to ... leaves.

Foliage is big business in the fall. Here in the Northwest, we can typically anticipate several weeks of glorious color from shrubs, trees, grasses, perennials and vines.

Mother Nature plays a substantial role in determining how - or even if - this autumnal magnificence plays out. Crisp nighttime temperatures, little or no heavy rainfall and clear, sunny days tend to bring out the best in fall foliage color.

But nothing is ever certain in the world of horticulture and plants are funny creatures. Some might throw out splendid fall hues one year only to balk the next, for something as seemingly insignificant as a shift toward more frequent irrigation or the installation of a high-intensity city street light that messes with a plant's internal clock.

This month's Q & A speaks to dependability; more specifically, plants that you can rely upon to offer splendid autumn color year after year.

October Q&A

Question: "I have several shrubs and trees that, for whatever reason, are erratic when it comes to fall color. Some years they're simply glorious, other years they look flat. Is it the plants, or me?!"

Answer: It's true that some years are better "color" years than others. It's also true that plant species can occasionally be a bit fickle when it comes to fall color reliability. Too much summer water or shade can definitely send normally stalwart performers into visual decline.

You can increase the odds by choosing species that have years of reliable fall color in your specific area. Many nurseries, garden clubs, plant societies and botanical gardens pay close attention to fall color and offer advice and even lists of plants that reliably offer up brilliant shades of red, purple, tangerine, coral, scarlet and yellow with minimal effort on your part.

Here are a few of my own favorites:

n American smoke tree (Cotinus obovatus): This native of the South almost became extinct during the Civil War years, when it was one of the few available sources of yellow dye. Thankfully, it has recovered in the wild and is now gaining stature as a lovely, easy-care, multi-seasonal small tree.

Our garden has a sport of Cotinus coggygria 'Purple Smoke,' which has terrific late fall color, but tends to be fairly sensitive to excess moisture and extreme cold. I've watched this cultivar die to the ground many times over the years, which has kept it from achieving that graceful, small-tree silhouette I had initially envisioned.

It's native cousin, on the other hand, is not at all fussy and can easily be trained with little pruning into a choice, 15- to 30-foot multistemmed deciduous tree. The rounded, deep green foliage of summer transforms in late September and early October into smoldering shades of vibrant scarlet, earthy purple and sassy tangerine-yellow, and shows little susceptibility to excess summer moisture, drought or cold winters.

This unsung native also produces smoke-like inflorescences of billowy pink in early summer that easily last a month, while older trees offer a gnarled limb structure and attractive dark, flaking bark.

n Oakleaf hydrangea (Hydrangea quercifolia): A great shrub that doesn't really start showing its true colors until Halloween. Rich, deep red, purple and orange last and last, often right up through the winter holidays.

Full sun gives the best show, and cultivars can be kept in the four-foot-high range with annual pruning. You'll miss some flowers, but this allows for a less leggy shrub form with even more foliage.

More terrific trees and shrubs with excellent and reliable fall color here in the Northwest include:

n Golden locust ((Robinia pseudoacacia 'Frisia'): lovely golden yellow leaves in spring and summer transform into even brighter hues come autumn.

n Sourwood (Oxydendrum arboretum): Slender foliage turns flame red early and hangs late into autumn.

n Katsura (Cercidiphyllum japonicum): Elegant branching structure and heart-shaped summer-green foliage that turns delicate shades of apricot, orange, yellow and sometimes even darkest maroon come fall.

The leaves don't last more than a week or two once they start to turn color, but the show is well worth it. The sweetly-scented pools of bright foliage collect in glistening pools around the tree trunk. This is such a lovely sight, I've actually seen cars pull to the side of the road in order to drink in the sight of a neighborhood katsura in all of its glory.