landscaping Slopes

Master Gardener: Landscaping on a slope is manageable with thoughtful design

Bill Sevier:  Ask a Master Gardener   

Saturday, August 20, 2016  

Q: I am trying to control water run-off and erosion on a slope in my front yard next to the street. Is there a best plant and a best way to do this? W.W., Sand Springs

A: The short answer is no. There are no easy generic solutions for slopes, and the solutions that are effective are not the same for each slope type.

Inclined areas of landscapes can have devastating erosive damage with extensive soil loss. So it is important to do what you can to stabilize these areas to simply prevent loss of your topsoil, if nothing else.

All slopes are not equal, they vary by degree of slope, soil texture and fertility, as well as amounts of sunlight received. All these factors, as well as cost and amount of effort required on your part, must be considered when creating a landscaping plan. One approach is costly and labor intensive. This consists of building tiers of various materials step-wise with drainage to handle the water flow.

When starting with bare soil, such as often found with new houses before any landscaping or planting, temporary measures can be used. These can include such things as blankets of burlap, jute, biodegradable plastic, or a temporary nurse crop of rapidly growing grass such as annual rye grass to stabilize the soil. All of these are biodegradable.

What to plant permanently on the slope to prevent erosion is the main decision to make. There are no “best” plants to use. Lawn grasses, such as Bermuda and fescue, are not the best choices; they are not nearly as effective as a mixture of perennials, shrubs, native plants and various groundcovers.

Most of the native grasses and forbs (wildflowers) originally found in the prairies in the Midwest have deep and tough roots, making them excellent choices for erosion prevention on a sunny slope. There is a long list of these natives that includes wildflowers such as coneflowers, black-eyed Susans, yarrows and many others. Non-native ornamentals like hostas, ferns and lilies can also be used, some for shaded areas.

Many types of groundcovers are beneficial, native and non-native. Most are evergreen and some spread vigorously. Plants such as vinca minor, liriope, Mondo grass, wintercreeper euonymus, ajuga and English ivy all are spreaders that tolerate shade and sun. These may have invasive problems if not controlled, but their hardiness and deep roots may be exactly what is needed on a hillside.

Low-growing shrubs are also useful. Short shrubs found in the juniper family, low-growing sumacs such as the cutleaf and Gro-low varieties are worth considering. There are varieties of forsythia that are short and might be considered as well as others.

After planting all your choices, add a thick layer of mulch between them. This will help keep out weeds and conserve water.

Remember, there are many more plants that would be practical on a slope. Decide what you have in terms of soil and sunshine, make a plan as to design and plant selection. Most slopes are manageable with thoughtful design.

Garden tips

§  August is a good month to start a fall vegetable garden. Bush beans, cucumbers and summer squash can be replanted for another crop. Beets, broccoli, carrots, potatoes, lettuce and other cool-season crops can also be planted at this time.

§  Discontinue deadheading roses by mid-August to help initiate winter hardiness.

§  Irrigated warm-season lawns such as Bermuda and zoysia can be fertilized once again; apply 1 pound N/1,000 square feet this month. Do not fertilize these grasses after the end of August. Do not fertilize tall fescue lawns in summer; fertilize in late September after it cools and again in November.

§  This time of the year is generally not the best time to prune, but if you have damage to trees and shrubs due to storms, prune out the damage now.

§  During peak heat of summer is not the best time to use post-emergent herbicides for broad-leaved weeds. For these herbicides to be effective, the weeds needs to be growing. Weeds will start to grow when it cools in early fall.