Talk about shady characters.

You'll find an enormous cast among evergreen begonias. They come in an amazing number of shapes and sizes, with more than 2,000 species and another 8,000 hybrids bearing flowers ranging from tiny, dangling blossoms to prolific, upright sprays. The leaves, too, may be no bigger than a fingernail or measure 2 feet across, and appear crinkly, striped, spotted or hairy.

How to choose?

Once you get past a handful of common bedding begonias, it seems there's a bewildering array of possibilities.

But divvy them up the way the experts do, and you'll be on your way.

The three main groups of shade-loving evergreen begonias are shrubs, canes and rhizomatous. Smaller groups and categories depend on who's entering begonia competitions and who's splitting hairs.

But the main three are distinct from tuberous begonias, which die back every year, and wax begonias (Begonia splendens), which are small bedding plants that thrive in sun on the Central Coast.

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SHRUB BEGONIAS

These are the easiest plants for beginners. The familiar ever-blooming - and nearly indestructible - richmondensis begonia belongs to this group.

Shrub begonias grow fast in filtered sunlight, with scores of tightly packed, upright stems emerging from the ground. All that bottom growth means they appear more lush and full than the cane begonias. Most grow 1 to 3 feet tall, although some can reach 12 feet tall.

In addition, they tend to shrug off powdery mildew and botrytis, which can afflict other groups of begonias. Many bear hairy leaves, which helps protect them from disease.

CANE BEGONIAS

Old-timers called these begonias “angel wings,” based on the shape of their leaves.

Now they're known as canes, because their stems look like bamboo, with a bumpy node at each joint.

Like shrub begonias, the canes grow fast in dappled sun - or even full morning sun - while their flowers dangle beneath showy leaves. But theirs is a more lanky growth. Some take several years to fill out, while others will always look sparse at the base.

In the meantime, they bloom like crazy, with the majority putting on a show whenever the weather warms up. In the right location, with plenty of indirect light, many will even bloom all year.

The down side is powdery mildew, which can attack with a vengeance during winter. Afflicted plants look terrible, but generally survive. Some folks spray their plants weekly to discourage the mildew from taking hold.

RHIZOMATOUS BEGONIAS

In true shade, without a flicker of direct sun, don't even attempt to grow canes or shrubs. Instead, try rhizomatous begonias.

These begonias differ from the others in that whenever their stems touch the soil, they root, forming an ever-expanding clump of upright shoots. They bear their waxy flowers high above their leaves, in a display so thick that during their heaviest bloom in late winter and spring, it's barely possible to see the foliage.

But once the show is over, the leaves are the thing for the rest of the year.

Some bear silver leaves, while others form spirals or unusual crests.

An offshoot of the rhizomatous is a smaller group, the Rex begonias, which are grown solely for their interesting leaf patterns. Some specialists even pinch off the flowers, to prevent them from detracting from the leaves.

Botrytis is the bane of rhizomatous begonias. Most of the plants bear leaves that are cupped. The shape unfortunately collects water, which can contribute to the disease.

During winter rains, it's a good idea to shield your plants with plastic. Overhead watering is not as much of a problem during warmer months, provided you water early in the day to give the leaves time to dry off before nightfall.

TUBEROUS BEGONIAS

These beauties demand perfectly drained soil, and are typically grown in containers or hanging baskets, where their large, waxy blooms can dangle over the sides.

Tuberous begonias are deciduous, so that portability comes in handy in the off-season.

The dusty, brown tubers go right on top of the soil, dimpled side up. Sprinkle potting mix over top, water thoroughly, then keep the top layer moist during the growing season.

Tuberous begonias grow best in filtered shade, out of the wind. They love humidity, and appreciate a quick spritz from the hose once or twice a day. To encourage sturdy leaves, apply a mild dose of a high-nitrogen liquid fertilizer twice a month until the end of May. Then switch to a low-nitrogen fertilizer to boost blooms.

In the fall, after the stems fall off, lift out the tubers, dust off the dirt and store them in a cool, dry location over winter.

WAX BEGONIAS

These remarkably durable plants are often sold as annuals in six packs. But on the Central Coast, they'll bloom nonstop for several years. They typically bloom in pink, red or white. Types with green button leaves will take a little shade, while those with darker or bronzy leaves will withstand all-day sun except in hotter, inland areas.

The little, ankle-high plants are good next to lawns, where they actually like capturing the overspray of sprinklers.

SEEDS OF WISDOM

Despite their differences, most begonias share a common desire for good drainage, rich soil and filtered sunlight - or at least protection from the sun during the middle of the day.

CARE AND FEEDING

All three types of evergreen begonias will grow in the ground on the Central Coast. But the soil must be fertile and drain well.

Plant rhizomatous kinds at the same level as their nursery pots. Bury the shrub and cane types an inch or two to stimulate dormant buds on the lower portions of their stems.

Water once or twice a week, depending on your conditions. Let the surface dry out. You can kill the plants by over-watering. If the lower leaves begin to yellow or drop off, they're getting too much.

During active growth, fertilize once a week with a quarter of the recommended dose of a balanced liquid fertilizer.

Prune shade begonias in spring.

With the shrubs, cut down all the stems that have bloomed, to force new growth from the base. You can wait until new shoots have started to emerge, so that your plant isn't entirely bare.

You can whack down cane begonias, too. Or simply shorten the stems, pruning them to outward facing buds, so that new growth will extend out from the plant.

Wait to prune rhizomatous begonias until after they've bloomed.

BEGONIAS ON THE INTERNET:

American Begonia Society: PO Box 471651, San Francisco, CA 94147, (918) 333-1587, www.begonias.org

Brad's Begonia World: www.bradsbegoniaworld.com

Kartuz Greenhouses: PO Box 790, Vista, CA 92085, (760) 941-3613, www.kartuz.com

Logee's Tropical Plants: Logee's Greenhouses, 141 North Street, Danielson, CT 06239, (888) 330-8038, www.logees.com

Van Bourgondien: PO Box 2000, Virginia Beach, CA 23450, (800) 622-9997, www.dutchbulbs.com

Joan S. Bolton is a local free-lance writer and garden designer. Her In the Garden column appears biweekly. She can be contacted through her Web site: www.santabarbaragardens.com.

April 22, 2008