The Well-Tended Perennial Garden - Gardening Book
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The Well-Tended Perennial Garden
Planting and Pruning Techniques
by Tracy DiSabato-Aust
338 pp, 131 color photos, 20 line drawings, 7 3/8 x 10 3/8", hardcover, © 1998 .
Generally speaking, plants that are not pruned in the autumn need to be cut back, or possibly deadleafed, in the spring. Perennials like Asarum, Bergenia, Helleborus, and Heuchera need to have their dead leaves removed, particularly if they have been exposed to windburn or sunscald. Epimedium and Helleborus need to be cut back early in spring so that the new flowers and leaves are not masked by the previous seasons tattered remains. Rotary mowers can be used on large plantings of Epimedium . The groundcover Liriope spicata also can be mown down in the spring. Moss phlox (Phlox subulata) may incur dead branches over the winter, or portions of the plant may die out, and these should be removed at this time. Evergreens may not need any additional pruning in the spring in some years, as their foliage stays fresh over the winter. Phlox stolonifera, Dianthus gratianopolitanus , and Arabis procurrens are just a few that usually fair well. Most often evergreen basal foliage doesnt need any additional pruning in the spring.
Certain subshrubs have their overwintering buds above ground, which classifies them botanically as woody plants but horticulturally they are classified with herbaceous perennials. They benefit from snow cover for protection and may experience tip die-back on the part of the plant above the snow line. Spring is the time to prune off those dead tips. This group includes heather ( Calluna vulgaris ), evergreen candytuft ( Iberis sempervirens ), lavender ( Lavandula ), germander ( Teucrium ), and thymes ( Thymus ). They may also need a hard cutting back in the spring if they start to grow leggy. . . . Lavender normally only needs its dead tips cut off in late spring or early summer, once all the woody growth has had a chance to break. Often the beginning gardener will prune back lavender hard before winter, only to be disappointed that it doesnt return at all the following spring. Lavender may need a hard cutting back (down to 4 to 6 in.) in spring every 2 to 3 years to hold a decent habit if it has become open and leggy or if its being used as a hedge. It can be cut back hard annually for hedging. . . .
I do most spring pruning in the early spring before new growth begins, usually sometime in late March or early April. Gardeners in milder climates [than Ohio] may need to get an earlier start. You dont want a lot of new growth in the way while you are trying to clean-up the old stems and leaves. If some new growth is hit during spring clean-up, no harm doneperennials are very forgiving and will be quick to fill in, but if you cut it too late you may be altering the plants ultimate height and even its flowering time on early blooming species.