Mulching: Mulch provides a number of benefits. They help to make the garden appear neater, conserve soil moisture, retard weed growth and moderate soil temperatures. There are a variety of materials that can be used as mulch. Examples would be bark, dry grass clippings, and hulls of various sorts. Mulch should not be applied right up to the crown of the plant to avoid problems with crown rots. Leave some air space between the mulch and the crown.
New perennial beds are mulched right after planting with about 2 inches of mulch. Additional mulch is applied annually as needed so that the overall depth doesn’t exceed 2 inches. Apply additional mulch in the spring as soils start to warm. Most perennials will not need additional mulch in the winter if soils have been properly prepared and the drainage is good. The exception would be for perennials that have been transplanted or planted late in autumn. Here, a 3-4 inch layer of loose mulch like straw, or evergreen boughs applied after the soil is frozen, helps to avoid frost heaving.
Watering: Water is a vital part in getting newly planted perennial gardens established. Soak the plants initially after planting and then check regularly to prevent drying out. Mulching helps to cut down on watering frequency. The general rule of thumb of one inch of water per week for established plantings holds true. Less frequent but deep watering encourage perennials to root more deeply and thus become better able to handle drought conditions.
The most common and time efficient way to water perennial gardens is to use soaker hoses. Many perennial gardeners will snake a soaker hose through the garden and leave it there all summer. When water is needed they will connect it to a faucet and turn it on. To make the hose invisible, bury it just under the mulch.
Fertilization: Most perennials do not require large amounts of fertilizer if the soils have been prepared properly. Many overfertilized perennials will produce excessive, soft growth and produce very few flowers. Many times perennials will tend to "lodge" or open up when overfertilized.
As a general rule, unless a soil test indicates otherwise, perennials can benefit from one pound of nitrogen per 1000 sq. ft. Granular fertilizers with a formulation of 12-12-12, 10-10-10, 5-10-5 or similar are sufficient.
Weed Control: Weeds that do appear in perennial gardens are often best controlled by shallow cultivation. If the weeds are perennial in nature, quick action is needed so that the infestation does not get out of hand. Cultivation again is the key, or you can make an very selective and directed application of glyophosphate to the weed. Use a foam paint brush to make such applications without the fear of damaging surrounding perennials.