How to Select, Plant, & Care for Herbaceous Perennials
Herbaceous perennials are valuable for a wide variety of uses in our landscapes. They beautify the home setting, increase property values, and provide greater depth to our daily experience. For a succession of bloom and full season of color, consider adding perennials to your garden.
Herbaceous perennials are grown primarily for their colorful flowers and foliage. Unlike annuals, which die after one growing season, herbaceous perennials grow anew from the roots each spring. Given the right location and proper care, these can be effectively used in beds, borders, cutting gardens, water edge settings, rock gardens, naturalized woodlands or meadow plantings, and make good container subjects. This guide will help give you herbaceous perennials a favorable start and allow you to get the most enjoyment out of them.
CHOOSING THE RIGHT PLANT:
You need the right plant for the right situation. A plant needs either sun or shade, moist or dry growing conditions, lean or rich soil. Your local garden center or Cooperative Extension office can advise you as to the proper selections for a given setting. Always look for healthy, vigorous plants when purchasing herbaceous perennials.
PREPARING THE GROUND FOR PLANTING:
Herbaceous perennials prefer a weed free, loamy, well-drained soil that is light and friable, yet able to retain moisture and nutrients. Whether your soil is sand or clay based, adding organic matter will improve its texture and water movement patterns, and will add some nutrients.
Thorough soil preparations prior to planting is essential to long term success. This is the only opportunity you will have to work the soil completely. Once plants are established, drainage and aeration cannot be substantially corrected without removing the plants. Test your soil to determine its pH, and adjust if necessary. Most herbaceous perennials will perform well if the pH falls between 5.5 and 6.5
Soil preparation work can be performed any time the soil is not frozen or excessively wet. Dig to a minimum of 12 inches, the deeper the better for root development. Raised beds with top soil is an easy-to-do English double-dig method. A 4 to 6 inch layer of organic matter such as well-rotted manure, compost, peat moss, decomposed bark or leaf mold should be worked into the soil by digging, spading or rotary tilling. In most cases, thoroughly mix 1 to 2 lbs. of superphosphate, rock phosphate or bone meal and 2 lbs. of an organic blend or a commercial granular fertilizer at the rate of 2 lbs. per 100 square feet into the top 6 inches of soil. This will be a benefit in successful plant establishment.
HOW TO PLANT:
Bare root perennials should be planted in spring or fall. Soak the plants for an hour or so prior to planting. Spread the roots and plant so the growth buds are 1 inch below the soil in good contact with the root system. Water the plants thoroughly. Potted perennials can be planted any time during the growing season. Carefully remove the plant from the pot. If the roots are wrapped around the bottom of the pot, gently tease them apart with your fingers. If they are too dense to accomplish this, a knife can be used to cut through the root mass. Spread the roots and set the plant at the same level it was in the container. Firm the soil around the plant to eliminate any air pockets around the root system. Water the plants thoroughly.
Do not plant too early in spring when soil moisture levels are high and temperatures are very cold. Planting at this time may ruin soil structure and result in poor root growth. Late season plantings should be completed a month before killing frosts so roots can get well established prior to the onset of winter. Extremely late planting can lead to frost heaving which pushes plants above ground and leads to their desiccation and death. All late season plantings should be mulched for their first winter to minimize the chances of winter damage.
Water thoroughly immediately after planting, and carefully monitor soil moisture levels until the plants are well established. Many perennials die due to either too much or too little water. Established plantings may require supplemental water through dry periods. Be certain to water deeply do not be afraid to check the soil to see to what depth the water has penetrated. Watering early in the day allows foliage to dry before dark and reduces disease incidence. Trickle or drip irrigation systems are water conserving and very helpful in preventing outbreaks of disease.
The proper use or summer mulches reduces moisture loss, cuts down on weeding and keeps plant roots cool and moist. a 2 to 3 inch layer of mulch over the crown of the plant as this can cause rot. Organic materials like compost, shredded leaves and bark are good choices. Plantings installed late in the season should be mulched for their first winter. Routine mulching of established plantings in the fall may be good insurance against winter injury. This is especially true for northern gardens containing shallow-rooted perennials such ad coral bells and bearded iris. Materials that can be used include evergreen boughs, marsh hay, or pine needles. Do not apply these winter mulches until the ground is frozen and be certain to remove them as soon as the plants commence growth in the spring. Mulching helps in all but poorly drained soils.
If your perennials are planted in a well-prepared soil, heavy fertilizing programs will not be necessary. A fertilizing application of an organic blend or a slow release, balanced garden fertilizer in early spring should be all that is necessary. Apply this fertilizer at the rate of 1 1/2 to 2 lbs. per 100 square feet. Should you prefer the use of a liquid fertilizer, you will need to make frequent applications. Poor soils, abnormally wet springs, or long growing seasons may necessitate additional fertilization in the summer months. Stop fertilizing by mid-summer so your perennials harden off properly in preparation for winter.
Some tall-growing perennials may require some kind of support. It is best to begin staking plants early in the season and continue the process as they grow. After plants have fallen over, it is extremely difficult to stake and preserve a natural look. A wide variety of stakes and staking methods are available to suit your plant's needs.
Purchase of healthy, pest-resistant varieties, correct culture, and good sanitation minimize pest problems with herbaceous perennials. Keep your plants healthy and learn to recognize problems when they first appear. Always destroy infected materials and never add them to the compost pile. Ask you garden center or extension agent for advice on using the proper pesticides. Make certain you purchase the right product, read the label and always follow directions.
Most perennials will require division to keep them performing at an optimum level. The need for this varies depending on the specific perennial. A good indicator of the need for division is dying-out of the center of the plant.
Each perennial zone rating indicating the northern limits to which it is reliably hardy. Ask your Cooperative Extension office or garden center what zone your garden falls into before selecting plants.