Tuesday, June 21, 2011

Common Landscape Errors

or ... It Isn't The Plant's Fault!

Written for the Davis Enterprise, June 23, 2011

Many landscape problems arise from the lack of nexus between landscape designers and landscape managers. In other words, it is the wrong plant, installed incorrectly, or managed improperly. If it's too big, someone is going to want to prune it. If it is in the lawn, they'll want to (appropriately) keep the grass away. If it isn't standing upright, they'll want to pull it up straight.
Here are some of the most common errors I see.
(For an illustrated version of this article, click here)

Mulch too close to the tree.

Mulch is very beneficial to the soil, but needs to be applied carefully. Moisture trapped around the bark of a tree or shrub leads to infection by Phytophthora. The result is crown rot: sudden death of the plant in hot weather. This disease requires warm, moist conditions to infect a plant. Mulch should always be several inches away from the trunk of any woody plant, especially in the summer.

Watering too often.

The single most common landscape mistake: watering too often, and not deeply enough. See crown rot, above. Constant moisture around the crown of a plant leads to attack by rot organisms. You can't just set the sprinkler timer and fail to adjust it for changing weather patterns. Water as slowly, deeply, and infrequently as possible.

Almost nothing needs water daily. The only exception might be plants that are rootbound in containers, and newly planted seedlings for the first week or so.

Staking too close, too tight, and too long.

Trees need to move in the breeze in order for their trunks to strengthen. They should not bang into the stakes. Usually we use two lodgepole stakes, pounded securely into the ground several inches east and west of the trunk (because our prevailing winds are from the north and south). A flexible tie is used in a figure-8 pattern, on each stake, at the point of the bend. The patented Redi-Stake™ is a single-stake technique that is used by the city and some arborists. This metal pole and rubber -tie system holds the tree securely and safely.

As soon as the tree can stand upright, the stakes should be removed, usually within one growing season. Ties should be checked monthly. Materials that could cut into the bark, such as wire, should not be used for tying up trees.

Wrong pruning tools.

Young men, hear me! Hatchets and axes are not pruning tools! Chain saws should only be used by trained professionals. Hedge shears are specialized tools used only for removing tender new growth.

Use a pruning saw or loppers. Pruning cuts should be clean to allow prompt development of callus as the tree naturally covers the wound. Ragged cuts invite pest and disease problems.

Note: pruning paint is no longer recommended to cover pruning wounds. The black paints absorb heat and increase damage. Whitewash on newly-exposed bark may be appropriate in some cases. Most often we simply let the wound heal naturally.

Topping trees.

Size control of trees might be necessary if a tree is planted under wires or overhangs, in which case poor tree selection is the issue. Public utilities must clear branches from wires, and do so with little consideration for the health or appearance of the tree. Our local utilities, PG&E and SMUD, have excellent resources available for choosing trees to plant under their wires.

If a tree must be kept lower than its natural size, proper training when it is young can be done to select permanent branches that have safe angles and good position along the trunk. Shortening a tree that is already too tall can be done by licensed, certified arborists who will "drop-crotch" the tree, cutting taller branches down to a point where an existing branch is already growing.

Plant professionals will not lop off ("top") all the growth above a certain point, as it results in rank, poorly-attached limbs that become unsafe. If someone proposes this for your trees, get a second opinion.

Wrong plant, wrong place.

Surface roots

Surface roots are part of the genetic makeup of certain species. Riparian trees that naturally would grow along streams and rivers have shallow roots that rapidly colonize newly deposited soil after floods. Willows, poplars, cottonwoods, and alders are unsuitable landscape trees because of their extensive, aggressive roots. White birches can be a problem in lawns, though the surface roots may be acceptable in landscaped, mulched areas.

Other species may develop surface roots if they are watered shallowly, but less so if watered deeply and infrequently. Evergreen magnolias and Chinese tallow trees are examples. Even sycamores and plane trees can develop surface roots if a constant shallow moisture source is available.

Shrubs under windows

I don't really understand why 10-foot-tall shrubs are planted under windows. There are plenty of low-growing shrubs to choose from. The most common mis-used shrub in this category is Photinia Fraseri, the red-tip shrub that is ubiquitous in California landscapes. A lovely large shrub in its place, it is often misplaced under windows and has to be pruned monthly. Then it looks ugly, and often slowly dies out.

Locally invasive plants, not confined.
Running species of bamboo, mint, ivy, creeping fig (among many others): each may be appropriate in a particular place, in a pot, or with appropriate barriers, but can take over a yard if not constrained. Choose a clumping bamboo; plant your mint in a nice pot; choose another species of vine. Save yourself and the future owner of your yard a lot of trouble.

Misapplication of herbicides.

The results can range from annoying to heart-breaking. Glyphosate sprayed around dormant roses has severely harmed many a rose garden. "Weed and Feed" applied to the lawn can be taken up by roots of nearby trees; the most common damage is to birches, magnolias, and maples. Continual use of pre-emergent herbicides in non-turf areas can lead to anemia as roots are damaged over time. Weed-killers have consequences. Read and follow label directions, and use as little as possible.

Continued use of plants with known pest problems.

Here are three categories.

Trees and shrubs that will die or be disfigured and for which there is no practical remedy. White alder. Leylandi cypress. The pests and diseases that kill them have been known in the horticulture industry for decades. There is really no excuse for the continued sale of these species.

Trees and shrubs with annoying pest problems that don't affect the vigor or health of the tree. Two examples. Honeylocust trees are infested by a gall-forming midge that causes most of the leaflets to drop off from late spring through mid-summer. They grow fine but get sparse and have lots of litter, so they are no longer recommended. Photinia Fraseri gets lacebug in the summer which makes the leaves ugly. It is manageable, but there are many resistant hedge species available.

Plants which will require regular spraying throughout the growing season to prevent damage.

Common garden geraniums, petunias and their calibrachoa cousins (Million Bells TM, etc.), get geranium budworm throughout the summer here. The caterpillar eats flower buds and leaves, and needs to be sprayed every few days throughout the bloom season. Most people aren't willing to do regular spraying in their gardens in order to keep flower blooming. Why not just plant something else?

Indeed: why not plant something else? There are hundreds of plant species to choose from, with low-maintenance options for most situations. With professional advice, you can start with a plant that won't require follow-up care. Watered correctly, it will thrive. Treat plants with respect and they will reward you!

Tree resources from PG&E

© 2011 Don Shor, Redwood Barn Nursery, Inc., 1607 Fifth Street, Davis, Ca 95616


Feel free to copy and distribute this article with attribution to this author.