By Dr. James R. Feucht, Extension Professor Landscape Plants, Colorado State University Cooperative Extension
If you can hardly get to your front door because the Pfitzers have taken over or if you can't see out of the windows because your shrubs are too tall, leggy and unkept, it's time to renew your landscape.
Overgrown shrubs such as lilacs, snowball bush, red-osier dogwood and mock-orange can be thinned now through a process called `renewal pruning.' You'll need a pair of sharp, long-handled pruners called "loppers", a sharp curved pruning saw and some hand pruners.
Remove as close to the ground the oldest canes and those that cross over each other. Leave medium-sized and smaller canes for this year's growth. Don't be tempted to cut the remaining healthy canes back from the top; this will only cause more bushiness on the exterior of the shrub and create more legginess.
New shoots will develop from the cane stubs you remove and will help fill-in the growth. By thinning the oldest canes every 2 or 3 years, the shrubs will maintain vitality without becoming over-grown. Avoid shearing of tips at all times; this promotes shading-out and weak growth. It also removes flower buds of lilac, snowball and similar shrubs.
Over-grown Pfitzers, upright junipers too close to the house that tend to lean outward, and evergreens originally planted too close together (see above photo) can be removed and replaced with more dwarf evergreens or those that grow slowly. Removal also gives you the chance to relocate new plantings for more space, correcting a problem started at the time of the original planting.
To replace evergreens close to doorways, steps, sidewalks and patios, use dwarf mugo pines, compact spreader varieties of juniper such as dwarf blue pfitzer, armstrong, sea green or mint Julep.
Upright junipers of slow growth include Gray Gleam, Canerti and Welchi. These rarely need pruning.
For very low evergreens, use creeping junipers. Some of the many types available include: Blue Rug, Hughes, Blue Chip, Buffalo and Webbers.
You also can consider replacing large, overgrown evergreens with more manageable dwarf varieties of non-evergreen shrubs.
For bright red stem color, dwarf Kelsey dogwood is excellent and is much easier to maintain than the larger red-osier types. Dwarf, compact European cranberrybush is a good replacement for the often ungainly snowball bush or, for fragrance, consider using the compact variety of Korean Spice Viburnum.
For June to August flowering, replace old shrubs in sunny spots with Froebels or Anthony Waterer Spireas. These plants can be treated much like garden perennials. Cut all stems to the ground in early spring. New growth will be dense and full of flowers by June. The same is true of orange-eye butterfly bush, flowering in late August, and Hidcote variety of St. Johnswort with its showy yellow flowers up to frost.
So, before you get out the hedge shears and chop back your aggressive shrubs as you may have been doing for years, think about renewing your landscape with plants that grow slower, stay compact by themselves or need only one cut back each spring.
You will be rewarded with less maintenance and more beauty in your yard. And, your local Colorado State University Cooperative Extension office offers information to help make good choices for your situation.
Photographs courtesy of Lynne Conroy.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010