When the late great plantsman Christopher Lloyd wrote a book a generation ago devoted entirely to foliage plants, he made no reference to a perennial named heuchera, or coral bells.

Today, that would be an unthinkable omission; heucheras have become as ubiquitous as hostas, and for similar reasons. They are conspicuously handsome foliage plants that brighten the gloomiest garden bed.

With their lush clumps of ruffled leaves, striking foliar patterns and a general air of vigor and health, they are eye candy in the garden center. Hence, the market has been flooded with too many varieties of heuchera. Nothing, it seems, exceeds like excess.

George Coombs, a research horticulturist at Mt. Cuba Center in Hockessin, Del., has spent the past three growing seasons trying to separate the heuchera wheat from the chaff. He found 83 cultivated varieties — that number alone may give you a clue to the glut — and planted six of each for evaluation. The trial reinforced a couple of realities: In the Mid-Atlantic, the heuchera struggles in an open and sunny location; it needs partial or full shade to look its best. Second, it rots in soil that remains wet. This combination makes the heuchera a fabulous solution to that awful garden condition, the sort of dry shade you find beneath trees or under eaves, as long as it is watered carefully until it is established. No more pachysandra!

You will certainly find a lot of variation: Some have deep purple leaves with silver veins, others have a bronze or bronze-green cast, some are chartreuse, others are a medium green but with a silver sheen. Leaves differ in size, as do the entire plants, they are generally much broader than high, but heights can differ greatly, from eight inches to 18 inches.

Heucheras begin to bloom in late spring. They produce clusters of small blooms on wire stems, typically a magenta pink, hence their other name, coral bells. In some varieties this flower display is highly effective, in others it is grudging. The real value of all the plants is their enduring foliage ornament, effective from April to November.

Coombs grouped his trial plants by their most obvious traits — silver or burgundy foliage, for example, or leaf size — and it became apparent that there was a lot of ornamental sameness. “We were blown away by how similar they were,” he said. “The main reason we wanted to do this was to address the glut of cultivars in the market. It can be confusing for a nursery professional, so to get the average homeowner to choose is an incredible feat.”

Abnormally wet periods revealed the heuchera’s weakness. “The worst ones are going to rot very quickly any time you get a decent amount of rain.” Interestingly, if an individual plant went downhill quickly, so did its clones. Velvet Night, Midnight Bayou and Hearts on Fire were among those that died mid-trial.

After prolonged, continual evaluation, Coombs picked the 10 best, surely a list worth keeping if you’re shopping for your shade garden this spring. They are, alphabetically:

Apple Crisp (Mt. Cuba Center)

Apple Crisp: The only dwarf variety on the list, it’s useful in small urban gardens and for niches. Green-leafed with a silver cast, it has lots of flower wands, blooming white.

Bronze Wave (Mt. Cuba Center)

Bronze Wave: Large and statuesque, its sycamore-like leaves are bronze-green above and maroon underneath. Flowers are small and creamy white but showy in massed plantings.

Cajun Fire (Mt. Cuba Center)

Cajun Fire: Spring growth on this medium-size variety is plum-colored maturing to reddish purple. Leaves are glossy and coarse. Flowers are attractive and creamy white.

Caramel (Mt. Cuba Center/ )

Caramel: Large in habit and leaf, this variety has novelty color. Its peach-colored spring growth ages to orange-yellow, with attractive white flowers.

Citronelle (Mt. Cuba Center)

Citronelle: This large variety has bright, electric-yellow leaves that darken a little in summer, with insignificant white blooms.

Color Dream (Mt. Cuba Center)

Color Dream: This medium-size plant is grown for its attractive silver leaf with blue-green undertones. Flowers are insignificant.

Frosted Violet (Mt. Cuba Center)

Frosted Violet: Large with purple foliage and a silver sheen, this variety’s blooms age from pink to white, giving a bicolored effect.

Southern Comfort (Mt. Cuba Center)

Southern Comfort: This variety is large-leafed and similar to Caramel in its peachy color, but much larger. The flowers are insignificant.

Spellbound (Mt. Cuba Center)

Spellbound: This medium-to-large plant has striking, cupped foliage that is silver with ornamental dark veins. The leaves are markedly cupped, showing off the purple undersides. Flowers are inconspicuous.

Steel City (Mt. Cuba Center)

Steel City: This medium-size, outstanding variety sports spring growth in a muted silver turning to blue-green, and the growth habit is dense and uniform. It has an abundance of soft pink flowers.

Frustratingly, there is no single or ready source for these plants; you’ll have to shop around to see whether local garden centers are carrying any of these cultivars, or search the Web.

Steel City is not only the cream of the crop, perhaps, but the least available. “I’ve been trying to talk it up to my nursery friends,” Coombs said. He hopes it will be commonly available in a couple of years.

A lot of people like the novel colors of caramel and its ilk. For what it’s worth, I don’t. I find them unnatural and difficult to use in a planting design.

I grow heucheras but limit them because their mounded, clumping habit makes them hard to flow visually with one another and other plants. Coombs said I should grow varieties bred from one of the two species breeders use, Heuchera villosa, because they are spreading and seamless. Bronze Wave would be a good choice, he said, or a variety that didn’t quite make the final 10 but is a fine plant for the Mid-Atlantic, Autumn Bride.

After three years immersed in heucheras, Coombs has an easy top choice. “After looking at 83 heucheras for three years, there was only one plant I took home,” he said. “Steel City.”