Perennial Flowers: Maintaining

Mulching
Mulching gives an orderly look to the garden, cuts down on weeding, and helps maintain uniform soil moisture. Organic mulches add some nutrients and humus to the soil as they decompose and improve soil tilth and moisture holding capacity. Most organic mulches should be applied after plants are well established and when there is reasonably good soil moisture. Pine bark nuggets, pine needles, compost, and shredded leaves are commonly used organic mulches for perennial beds. A 2- to 3-inch layer of mulch is applied at planting. Additional mulch is added in early spring to maintain the desired mulch depth. A word of caution --- heavy mulches that hold moisture can be detrimental, particularly to plants subject to crown rot.

Watering
Soil type, plant species as well as growth stage and temperature influence watering frequency. Plants grown in a clay soil that has been properly watered may need to be watered only once a week. Plants grown in a sandy soil may need watering several times a week. Water requirements will vary with the time of year, amount of sunlight or shade, plant growth, and other environmental factors. Most plants need 1 inch of water per week, but may require more when flowering or when exposed to high temperatures or windy conditions. After watering, allow the soil to dry moderately before watering again.

A soaker hose is excellent for watering. Water seeps directly into the soil without wetting the leaves and flowers. Sprinklers wet the flowers and foliage and makes the plant more susceptible to diseases.

Weed Control
Mulch and proper plant spacing are the best ways to minimize weed problems. A preemergence herbicide can be used to control many weeds. Some preemergence herbicides are applied before planting, others are applied after planting but before weeds emerge. Any herbicide used in flowerbeds must be chosen carefully. Read the label: no one herbicide can be used safely on all flowers. Herbicides that are labeled for some but not all flowers include: Betasan, Surflan, and Treflan. Time and rate of application will vary with the herbicide selected. The bed should be weed-free when the preemergence herbicide is applied. Only a few postemergence herbicides can be used to control grassy weeds after flowers have become established. Some weeds will still need to be pulled by hand -- weeds are easier to pull after a rain or irrigation.

Fertilizing
Most perennials are not heavy feeders. A light fertilization of 2 to 3 pounds of 5-10-10 or 10-10-10 per 100 square feet should be applied in early spring. A second application is often made in mid-summer at the rate of 1 1/2 to 2 pounds per 100 square feet. Take into consideration the amount of plant growth -- if growth is adequate you may not need to fertilize. Too much fertilizer will promote foliage and possibly diseases without necessarily promoting flower production. It is not necessary to remove the mulch before fertilizing. Water after applying fertilizer; this will wash fertilizer off the foliage, prevent foliage burn, and will make the fertilizer available more quickly.

Deadheading
After perennials have bloomed, spent flowers and seed pods should be removed. Keep in mind that some perennials do not require deadheading since the seed pods are either not very visible or are quite attractive. Cut the flower stem down to a healthy leaf or side branch. This will keep the plants looking neater and will prevent them from wasting energy by producing seeds. Some plants produce so many seeds and volunteer plants that they become overcrowded and invasive. Deadheading will reduce the problem. Some perennials will rebloom if cut back after the first flush of flowers.

Pinching
Some plants will grow thicker and fuller if the terminal growth is pinched. This reduces the height and reduces the likelihood that the plant will be blown over by wind and rain or from the weight of large, heavy flowers. The result is a more compact plant with more but sometimes smaller flowers. Pinching often delays flowering. Plants that respond to pinching include chrysanthemums, asters, and phlox. Start pinching in early spring when the shoots are several inches long and discontinue by early July.

Consumer Horticulture | Perennials Home

Prepared by: Erv Evans, Consumer Horticulturist, NC State University