Maintenance

Water the perennial garden when the soil becomes dry. This will vary with soil type. Watch new beds for signs of wilting. Young, newly planted perennials will need more frequent watering than mature, established plants. Water throughly and try not to splash water on the foliage. Use a trowel to check the soil for moisture - soil should be moist 4 to 5 inches deep. It is better to water thoroughly and less frequently than to apply many superficial waterings.

Apply a 2-inch layer of mulch over the bed or border every spring, tapering it off gradually near each plant. You may apply a layer of winter mulch 4 inches deep after the soil is frozen to a depth of 2 inches. This helps prevent winter injury, especially heaving. If you apply mulch too early, rodent problems may develop. Use an open, fluffy

material, such as pine boughs, pine needles or excelsior over the entire bed. Remove this layer the following spring after the danger of severe frost has passed. A winter mulch can help unreliably hardy plants survive the winter.

Staking Tall Plants

You may have to stake tall plants as they grow. Stake each stem individually instead of trying to tie them all together. Tie the plant to the stake with plastic strips or wire covered with a plastic coating. Make a double loop of the wire with one loop around the plant and the other around the stake. This keeps the stem from rubbing against the stake. For tall, arching plants, make or purchase circular rings and attach them to the stakes to support plants and to maintain their natural form. A three-legged support called a peony hoop is less obstructive than poles in the garden. Tomato cages can be used in the same way.

Fertilizing

If desired, apply fertilizer as growth begins in the spring. Because many soils have adequate phosphorous and potassium but are deficient in nitrogen, use a complete fertilizer every 3 or 4 years and supplement it with a nitrogen-based fertilizer other years. However, most perennials are not heavy feeders. Organic matter added at the time of planting can provide sufficient nutrients for many years and eliminate the need for fertilizer. Exceptions are astilbe, chrysanthemum, delphinium, lupines and summer phlox, which should be fertilized every year. If plants are not vigorous and foliage is light green or yellowish, applying a nitrogen-based fertilizer would probably be beneficial.

Weed Control

Cultivate perennials as frequently as needed to control weeds. Most weeds can be killed by using an action hoe or similar tool. Work the top half-inch of the soil. If you cultivate much deeper, you can injure plant roots. Frequent, shallow cultivation is better than occasional, deep cultivation. Try not to walk in the beds while weeding. Soil can be easily compacted, which limits root growth.

Blooming

"Dead-head" - that is, remove old flower heads, after blooming unless the fruits are ornamental. This prolongs the flower period of many perennials, especially dianthus, coreopsis and shasta daisy.

A few species will bloom a second time if the stems cut back after flowering. Examples are delphinium, false indigo and globe thistle. The flowers won't be as numerous on the regrowth, but cutting back does result in a longer, although not continuous, flowering period.

Propagation Methods

Dividing

Many vigorous perennials crowd themselves and require dividing every few years. Also, the most aggressive types can escape and choke out other plants around them. Dividing is often done in the fall in warmer areas of the country, but in Zones 4 to 6, divide plants in the spring while they are still dormant. This avoids subjecting the newly divided plants to harsh winter

temperatures and reduces the chances of heaving.

The method of division varies among types of perennials. In general, vigorous new shoots from the outside of a clump are preferred for replanting, but you can use all shoots, if desired.

To make digging easier, water the bed well a few days beforehand if the soil is dry. Before dividing, prune the plants by half if stems are still present. Dig out the entire clump. Divide the healthy living portions into smaller clumps by working them apart with your fingers or making small cuts with a knife. Divide large, dense clumps using two spading forks back-to-back. In general, replace one or two healthy divisions in the original hole and plant the others elsewhere.

Some species have large taproots and should not be divided or moved unnecessarily. Examples are baby's-breath, balloon flower, butterfly weed and lupine.

Other propagation methods

There are several other ways to propagate perennials. You can propagate chrysanthemums by stem and root cuttings; iris by rhizome pieces; anemone and perennial phlox by root cuttings; and peonies and bleedingheart by taking roots with one or more "eyes". Consult other gardeners, catalogs or books for more details on specific methods.