Johnny-jump-ups thrive in cool weather

These small cool-season flowers put the rainbow to shame: You can find cultivars in purple, orange, yellow, lavender, pink, red, white, black, and often with two or three colors on each blossom.

They're tough, hardy plants that bloom for months under the right conditions, fading away only when faced with intense heat. Some violas will form a lush, compact mound; others have a trailing habit.

No matter where you put them—in a window box or flower pot, a rock garden or around the border of a flowerbed—a clump of these velvety, five-petaled faces will make your garden hum.

Common name: Johnny-jump-up, love-in-idleness
Botanical name: Viola tricolor
Plant type: Typically grown as annuals or short-lived perennials.
Zones: 3 to 9
Height: 3 to 10 inches tall, depending on cultivar
Family: Violaceae

Growing conditions
Sun: Part sun. Happiest with morning sun and afternoon shade.
Soil: Rich and well-drained.
Moisture: Cool and moist.

Care
Mulch: Mulch will help preserve moisture in the soil.
Pruning: None needed.
Fertilizer: Mix in a slow-release fertilizer when you plant violas, or use a balanced fertilizer throughout the growing season.

Propagation
• By seed; often self-seeds.

Pests and diseases
• Vulnerable to powdery mildew, crown and root rot, and fungal leaf spots.
• May attract slugs, snails, aphids, or violet leaf midges.

Garden notes
V. tricolor is a cool-season plant. If you live in a warm climate, plant it in fall so you'll have months of color before it wilts in the summer heat. If you live in a cold-weather climate, plant it in spring so it will flower through the summer months. In some climates, a hardy cultivar with enough mulch might even survive a mild winter. .
• Plant at the front edge of a flower bed or in a container.
• Plant between spring bulbs; the viola blooms will take over as the bulbs' flowers fade.

Cultivars
• Many cultivars available. Pictured above: PanAmerican Viola 'Sorbet Coconut Duet'

All in the family
• The genus Viola contains about 500 species, including pansies (V. x wittrockiana), sweet violets (V. odorata), and bird's-foot violets (V. pedata).
• Garden violas can be one of two species: V. tricolor or V. cornuta (also called horned violets or tufted pansies). V. cornuta, native to the Pyrenees in Spain, is a little bigger than V. tricolor and may be lightly scented