Shaping Up Shrubs: Maintaining Shrubs

A LITTLE LEANER. Shrubs grown in climates, spaces and conditions they can handle are better performers, therefore maintaining them includes only the basics – proper watering, pruning, fertilization, and insect and disease control, Hill said.

Therefore, contractors who are accustomed to needy lawns should scale back when it comes to shrubs, Proud said, suggesting "leaner" maintenance.

The most common culprit is overwatering. "Everyone’s response to a problem is ‘let’s water,’" Troutman said. "But that’s not always the best thing. There needs to be room in the soil for air to reach the root system of an active plant. Drainage should be so that it drains through the soil or away from the plants."

A classic watering mistake concerning shrub health is incorrect irrigation zoning, according to Proud and Troutman. "When the shrubs, turf and flowers are all on the same system, the flowers are underwatered and shrubs are overwatered," Troutman explained, pointing out that many shrub diseases occur because the leaves remain wet for long periods of time. "For example, the red-tipped Photinia is sensitive to leaf spot. Once a leaf is infected, disease spores are splattered onto other leaves from rainfall or irrigation and the leaf spot spreads throughout the entire plant – new leaves being the most susceptible.

"If you don’t learn these things and put this shrub on the shady side of a house under a wet spot and put the sprinklers on risers so they spray above the plant material and don’t get the leaves wet, you’re going to kill that plant," Troutman continued. "But if you do know these things, you’ll recommend the plant be moved to an area with a lot of air movement, where it isn’t under a tree or roof and you’ll use drip irrigation, pruning only when necessary. That’s what creates a disease-free plant."

Contractors recommend different approaches concerning fertilization. Hill uses deep-root fertilization in the fall with a time-released fertilizer. "We often add a spring deep-root as well, using a water-soluble, balanced fertilizer," he said.

Environmental Care fertilizes shrubs one to three times per year, depending on the plant’s needs and location. For example, certain shrub species in Florida need more fertilization than shrubs in other areas of the country, Troutman said, pointing out that he uses a slow-release granular fertilizer because shrubs aren’t fertilized as often as lawns so the product must last longer and requires uniform application. "Occasionally, we’ll do foliar applications on plants that aren’t responding," he added. "Or we use micronutrients, but we are very careful with this product because it can stain buildings."

Proud, on the other hand, said overfertilizing creates maintenance nightmares. "Too much fertilizer only increases plant growth and, therefore, maintenance needs," she said. "Besides, there is plenty of fertilizer available in the soil. If you don’t fertilize or fertilize less, you won’t have an issue unless you are in an area with sandy soil and the nutrient retention in the soil is lousy or if the soil wasn’t amended properly before the shrub was planted."

To banish weeds from shrub beds, Troutman suggested using a preemergence weed control one to three times each year. "It doesn’t eliminate all the weeds, but it reduces labor," he said, explaining that preemergence herbicides save man-hours associated with labor-intensive hand weeding.

But once preemergence control is used, weeds surrounding shrubs should be spot-sprayed with a nonselective herbicide because pulling them can break the preemergence barrier, creating holes where additional weeds can sprout, Troutman added.

ONE SNIP AT A TIME. Most people describe shrub pruning as an art, but, actually, it’s a science, pointed out J.R. Feucht, retired landscape plant specialist and professor, Colorado State University Cooperative Extension, Fort Collins, Colo. "As a result, reference materials place emphasis on shape and form and less on how a plant responds to pruning," he said. "This often leads to butchering."

Shearing, which is "the process of using hedge clippers to create funky shrub shapes," Troutman said, is popular in landscaping because a shrub can be sheared very quickly and doesn’t have to be trimmed again for some time. A shrub also can be clipped too closely with this method, meaning the plant takes much longer to recover.

Because shearing removes growth continually to control shrub size, correct pruning rarely can be practiced. "We’ve had instances where clients say, ‘If this shrub grows ½-inch above this line, you’re fired," Troutman related. "But if you continually shear a plant at the same level, it creates a whole bunch of buds at the tip of that plant. And as it’s cut again, it produces more buds. We call those buds knuckles – the leaves that are produced there are smaller and not as healthy."

Shearing also is popular when clients require stiff, formal, English garden-like hedges that are vertically cut. "This is also bad for the plant because the lower leaves don’t receive enough sunlight," Troutman explained. "The base of the shrub should always be wider than the top. If you don’t do that, you’re always going to see healthy growth at the top of the plant and stems at the bottom because they haven’t received enough sunlight."

Selective pruning is the preferred method for shaping shrubs and is done for health improvement reasons, primarily. This includes removal of diseased, insect-ridden, dying, interfering and weak growth, Feucht pointed out. Proper pruning vs. shrub sculpting results in better flowering and healthier foliage, he said. "Pruning to shape the plant can be legitimate, but exercise care," Feucht advised. "It is too easy to end up with a sheared plant during the shaping process."

Troutman prefers a similar method, pruning stems that escape the shrub to maintain its shape and prompt healthy bud growth.

Consequently, following a regular maintenance schedule allows for hassle-free pruning. Since a neglected shrub is harder to prune, pruning should begin before a plant fully occupies its space. "In pruning a shrub, we normally want to encourage latent bud growth from the base," Feucht said. "If this is done in late winter, annually, or as needed, heading-back of spring-flowering shrubs seldom is necessary. This type of pruning – thinning and renewal – not only maintains a healthier, more attractive plant, but allows the contractor to do the major pruning work in the less busy season."