Versatile Violas

The National Garden Bureau has declared 2007 as "The Year of Violas," and for good reason. Violas are now competing with their pansy cousins as "superstars" of the cool-season garden. Always easy to grow, newer viola varieties offer larger flower size, along with excellent heat resistance and cold tolerance, for exceptional garden performance. The flower color palette is expansive, offering beautiful pastels and sparkling jewel tones. Some flowers have two, even three colors. Many have unique patterns and markings. The fresh green foliage provides a canvas that makes the abundant flowers shine.

Violas have gained popularity in recent years with gardeners in all regions of the country. In northern climates, violas grace the garden during the spring and early summer, often flowering into the fall. Newer viola hybrids are exceptionally cold hardy and may even survive northern winters with proper care and plenty of mulch. In the South, violas are essential in the fall garden, providing continuous bloom through winter and spring, lasting until summer’s heat takes its toll.

Violas have been celebrated throughout history, not only in gardening, but also in literature, medicine and art. Most of the historical references probably refer to the Sweet Violet (Viola odorata), a popular perennial today that was one of the first flowers to be grown commercially. Violas came from Europe, where they grew wild throughout the region, and were familiar as early as the 4th century BC to the Greeks, who cultivated the plants for medicinal use.

Viola is a large genus of about 500 species that includes many popular wildflowers and garden flowers such as pansies, sweet violets and Johnny-jump-ups. Reference to the modern day viola can be found dating back to 1633. Gerard’s The Herbal describes the Heartsease (Viola tricolor) as having "forme and figure like the Violet, and for the most part of the same bigness, of three sundry colours, … that is to say, purple, yellow, and white or blew." Heartsease has been used for centuries as an herbal treatment for a wide range of ailments including epilepsy, asthma, eczema and other skin diseases. It was also used to treat respiratory problems such as bronchitis and whooping cough, as well as rheumatism. The flowers, leaves and roots of Viola are still used by many herbalists today.

Garden violas are represented by two species. One species is Viola tricolor, or Johnny-jumpup. This perennial is native to Europe and Asia, grows about 6-10 inches high, and produces small, nickel-sized flowers in purple, yellow and white with interesting marks or whiskers. Johnny-jump-ups are often grown as an annual. It was grown by Thomas Jefferson, who noted that he planted it at his birthplace, Shadwell, in 1767.

The other is Viola cornuta, sometimes called tufted pansies or horned violets. Native to Spain and the Pyrenees, V. cornuta grows throughout temperate regions of the world. The green leaves form spreading, perennial, evergreen rosettes. Plants are compact, up to 8-10 inches tall,

Closely related is the garden pansy, Viola wittrockiana, this short-lived perennial has larger flowers than V. tricolor or V. cornuta. Pansies reach a height of about 8 inches tall with single colored or face patterned flowers that measure 2-3 inches across, though some hybrids have even larger flowers. Pansies are generally grown as annuals.

Violas can be grouped in several different ways. Plants may have a compact, mounded growth habit or a spreading, trailing habit. Flowers can be small—under 1-inch in diameter, or large — over 1-inch. Varieties are openpollinated (that "come true" from seed) or hybrid. Hybrid varieties offer exceptional garden performance, good flower production and uniform growth. ‘Sorbet™’ violas come in more than thirty colors including beautiful pastel and two-tone colors on compact plants reaching 6-8 inches tall. ‘Penny™’ violas are available in shades of light blue, deep blue, purple, violet, white, yellow, orange and red. Some have whiskers and blotches (faces) others are bi-color. They have a mounding garden habit and flower continuously.

In 2006, ‘Skippy™ XL Red-Gold,’ a hybrid Viola cornuta, was the first viola to win an All-America Selections award for superior garden performance. Its large, 1 1/2-inch flowers are ruby red with violet-red shading below a golden yellow face with the trademark whiskers or markings. The ‘Skippy™’ series has many other colors, including bi-colors. One of the largest flowered violas is the hybrid ‘Patiola®’ series, combining the flower size of pansy with the hardiness of violas. Flowers grow to 2 inches in diameter and bloom in yellow, blue, orange and violet. The newest color in the series is brick red with a golden yellow center.

Trailing violas have a low growing, spreading habit that is perfect for hanging baskets, containers or use as a groundcover. There are several hybrid varieties available. ‘Erlyn’ produces tricolor purple and yellow flowers that cover the plant. The ‘Splendid’ series has one-inch flowers in white, yellow, and blue and yellow. Plants spread up to one foot in diameter.

In Missouri, violas can be planted in late fall where they often survive our (relatively) mild winters or in early spring. Select healthy, compact plants with green leaves. Avoid plants that show signs of yellowing which may indicate a problem with the roots or a nutrition problem. Plants that are stressed in the container may take more time to become established in the garden, often develop poorly and never flower well. Also avoid plants that have a lot of roots growing through the bottom of a plastic container. They will be hard to remove without damaging the root system.

Violas prefer a rich, moist, welldrained soil with plenty of organic matter. Mix a slow-release fertilizer into the soil at planting time or occasionally fertilize with a balanced fertilizer. Water when the soil is dry to maintain even moisture.

It is important for violas to receive enough sun yet be protected from extreme heat. In warm climates, violas do best when they are shaded during the hottest part of the day. Morning sun and afternoon shade are ideal. Mulch helps keep the soil cool and moist. Violas grow in a wide range of temperatures from 30-80 degrees F. They will even survive overnight temperatures in the upper teens if it warms up during the day. Plants flower sparsely and eventually die when temperatures stay above 90 degrees F for extended periods of time.

Plant mounded violas about 6-8 inches apart. Trailing or spreading varieties can be planted 10-12 inches apart. To promote blooming and extend the flowering period, remove or deadhead faded flowers by pinching off the blooms at the base of the flower stem. Revive leggy or overgrown plants by cutting them back to about 3-4 inches tall. Violas often self-seed, though newer hybrid varieties will not produce plants that look like the ones you planted.

Violas have relatively few disease or insect problems. Diseases such as powdery mildew or botrytis can be avoided by planting violas in an area that receives plenty of light and good air circulation. Aphids can be washed off with a strong stream of water, or treated with an insecticidal soap. Viola’s size, compact habit and long flowering period are perfect for containers, hanging baskets and garden beds. Mounded plants make a lovely edging along a path or to define a garden border. Trailing varieties are exquisite in hanging baskets, filling crevices in rock walls and tumbling over the edge of containers and window boxes. Violas can be mixed with other garden flowers for stunning combinations in garden beds or containers. They make a wonderful choice for planting with other cool-loving garden flowers such as snapdragon, calendula and dianthus. Alternatively, violas can be tucked between spring flowering bulbs such as tulips and daffodils to fill the space as the bulbs fade.

Credit: National Garden Bureau

David Trinklein
Associate Professor Plant Sciences
TrinkleinD@missouri.edu