Perennials are attractive additions to the home landscape. However, they require good care. The following are important cultural practices.
Mulches are an excellent way to reduce maintenance chores in perennial plantings. Mulches conserve soil moisture, reducing the need to water. Mulches also help control weeds by preventing the germination of annual and perennial weed seeds. Additionally, mulches prevent the splattering of soil onto foliage and flowers. This keeps the plants cleaner and may reduce disease problems.
Excellent mulching materials for perennial beds and borders are shredded bark and wood chips. These materials are widely available, attractive, and long-lasting. Other possible mulches include ground corncobs, shredded leaves, dry grass clippings, and pine needles.
Place 2 to 3 inches of mulch around the perennials. However, do not place the material directly over the plant crowns.
Many perennials perform best when they receive 1 to 1 1/2 inches of water per week, either from rain or irrigation.
When watering, soak the soil to a depth of 8 to 10 inches. Watering frequency is largely determined by soil characteristics, weather conditions, and plant species. A thorough soaking once a week is adequate for most perennials.
Perennials, such as sedum, coreopsis, blazing star, and most ornamental grasses, possess excellent drought tolerance. Once established, these drought tolerant perennials require little or no watering.
The removal of spent or faded flowers (deadheading) can prolong the bloom period for some perennials. It also improves the appearance of many perennials as the spent flowers are often unattractive. In addition, deadheading prevents fruit formation. Fruit development diverts a large amount of the plant s energy. This diversion of the plant's resources may weaken the plant, resulting in fewer flowers the following year.
For most perennials, an application of 1 to 2 pounds of an all-purpose garden fertilizer, such as a 10-10-10, per 100 square feet is adequate. Excess fertilization produces weak, leggy growth and inhibits flowering. Early spring (late March to mid-April) is the best time to fertilize perennials in Iowa.
Many perennials need to be divided periodically to control size, retain vigor, or promote flowering. Division is also an excellent way to propagate a prized perennial. The best time to divide perennials varies with the different plant species. Specific times can be found in RG-319 "When to Divide Perennials."
Most perennials die back to the ground after the first hard frost in fall. The dead plant debris should be cut off and removed in late fall or early spring of the following year. Removal of the dead material improves the appearance of the area. It may also reduce the severity of disease problems as plant pathogens often persist in the debris.
This article originally appeared in the July 26, 2002 issue, p. 104.