Garden pansies (Viola x wittrockiana) are among the best plants for cool-season flower beds, lending a cheerful splash of color when the rest of the landscape is leafless and dull. As long as temperatures do not exceed 80 degrees Fahrenheit, a pansy plant will continue to grow and flower. Fertile, moist soils with good drainage and abundant sunshine encourages the pansy to prosper and delight.
Soil and Fertilization
A fertile soil that is rich in compost or humus is ideal for growing garden pansies. It should be moist but never so wet that it is soggy, which will encourage fungal rot of roots and stems. Good drainage is needed and in heavy clay soils can be improved by adding organic matter. Low-lying flower beds should be mounded with extra soil to ensure the plants' roots are not subjected to flooding after rains.
The pH of the soil can range from acidic to slightly alkaline (5.5 to 8.0). The addition of organic matter to any soil often aids in making the soil pH hospitable for pansy growth and flowering.
Fertilizing pansies can increase flowering production and plant size. If the soil is well-prepared with organic matter, less fertilization is needed. Sprinkling a slow-release granular fertilizer atop the soil after planting provides trace minerals as the plants establish. Once warmth returns by late winter and spring, however, the application of a liquid fertilizer every 2 to 4 weeks can greatly improve the vigor and floral display.
Although grown as annuals, garden pansies are actually very short-lived perennials. When nighttime temperatures are below 65 degrees Fahrenheit, pansies prosper. The plants would endure much longer if it wasn't for the excessive heat of the summertime, when temperatures consistently reach above 80 degrees Fahrenheit. Conversely, in regions with very cold winters, prolonged exposure to subfreezing temperatures, especially without a protective snow cover, will kill foliage and roots as the soil freezes solid.
In the northern United States, pansies are often planted in early spring as a companion to spring bulbs like daffodils and tulips. As the temperatures slowly warm as summer approaches, the pansies are either pulled up and replaced with traditional summertime annual plants, or allowed to grow and bloom until the heat stunts the production of flowers. In the milder winter regions of the American South, garden pansies are heavily used to bring color to flower beds from mid-autumn until mid-spring. The fall planting quickly results in establishment of roots and flowering even across midwinter. By early spring, these pansies quickly display repeated flushes of flowers and continue until the heat of late spring when they are replaced with more summer-looking plantings.
A full sun exposure is ideal for rich green foliage and abundant flowering of garden pansies. However, partial shade can provide enough light for good flowering displays, such as under the branches of deciduous trees from autumn to leaf-out in spring. As long as 3 to 4 hours of direct sunlight can reach the the pansies, leaf growth and production of flowers will continue. If light intensity or duration is too low, the plants do not increase their size and the number of flowers per plant is often 2 or less at a time, or simply absent.