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written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Twenty years ago the landscape bed in front of the Benton County WSU Extension Office was planted with boxwood, mugho pine, and juniper. The plants were watered with drip irrigation and mulched with lava rock. The boxwood quickly died (due to winter injury), leaving the pines and junipers. These plants thrived and eventually grew quite large, requiring regular pruning to keep them from overtaking the bed, obstructing the view of the office, and tripping visitors. Despite the regular pruning, the bed required little care and used only limited amounts of water… since both pines and junipers don’t require lots of water to keep them happy.

In this way the planting functioned as a low-water-use landscape bed, but it lacked interest… and color! Inspired by other colorful low-water-use landscapes, I asked a group of WSU Master Gardeners to help redesign and plant this landscape bed. The Benton County facilities crew assisted us by removing the old pines, junipers, and lava rock mulch. This was no easy task, since the plants had grown in the bed for a long time and were well established. After the shrubs and lava rock were removed, the Master Gardeners worked long and hard to remove the remaining shrub roots and many rocks. A layer of alfalfa hay was spread over the top and then tilled into the bed to loosen and condition the hard packed soil.

The removal of the old plants, roots, rocks, addition of organic matter, and tilling were all very hard work, but were a critical part in creating the new landscape. After the soil preparation, two very heavy and attractive basalt rocks were strategically placed to provide focal points and dimension to the bed. A fountain or piece of statuary might have been a nice addition too, but they were concerned that their maintenance would create undesirable extra work..

The Master Gardeners met to select plants and design where they would go in the bed. This landscape bed is in an area particularly tough for growing plants… it faces southwest and is surrounded by concrete. It’s also situated next to a light colored building. All these factors create an extremely hot, stressful location for growing plants. The Master Gardeners wanted to pick plants that could withstand the heat, didn’t have special soil requirements, didn’t require much water, and didn’t have significant pest problems requiring high maintenance. They also wanted plants that were easy to grow and could provide color and interest to the bed throughout the year.

Some plants were planted in the fall because of their availability and additional plants were added to the bed in the spring. After planting, the bed was mulched with two inches of shredded bark. This helped retain soil moisture and control weeds. More bark was added this summer.

No irrigation water was available in the fall, so the plants were hand-watered to aid in establishment. In the spring, drip irrigation was installed in the bed and adjusted to fit the needs of the plants. Over the recent growing season the small plants have grown and provided color all spring and summer. As time goes by, these plants will grow even more, filling in the open spaces in the landscape… although a few more plants still need to be acquired and planted. Stop by the office and see it sometime!

If you want to design a water conserving landscape bed, here’s a review of the simple steps the WSU Master Gardeners took in creating our low-water-use landscape demonstration bed:

1. If you’re creating a brand new landscape bed proceed to step two. If converting an already established bed, your first step is to remove the existing plants, landscape fabric, and mulches. If mulched with bark, rake the mulch off and put it aside for later use. Get rid of any rock mulches.

2. Prepare the soil by tilling. Spread a 4-inch layer of the organic matter across the bed and till it thoroughly into the soil. The organic matter can be clean alfalfa, well rotted compost, or peat moss.

3. Remove any plant debris and large rocks left in the bed. Grade the bed so that the soil is several inches below the bed’s outer edge. This helps contain the bark mulch without special edging.

4. Consider what items you might want to add to provide focal points or special interest to the bed, such as rocks, statuary, or a fountain. Placement of large rocks will look more natural if the rocks are partially buried or mounded with soil on at least one side. Restrain your use of focal points… only one or two is best. Too many items will create a “busy” look and detract from the plants and overall appearance of the bed.

4. Select “drought tolerant” plants, those with similar low water requirements. Keep in mind flower color, time of bloom, and the plant’s mature height and spread when selecting your plants and creating your bed’s design. Plant the perennial flowers, shrubs, and trees, making sure their roots are loosened and that the plant is situated at the same depth it was growing in the nursery. Fall or early spring are the best times for planting.

5. Install drip irrigation. Monitor the soil moisture and adjust emitter sizes and timing of applications as needed for soil and weather conditions. You will need to insure that the plants get adequate water, especially during the first six months to a year as the plants become established.

6. Apply two to four inches of bark mulch. Reapply the mulch every year as needed to maintain that depth.

Here is a list of the plants already planted in the demonstration landscape bed or will be planted soon:

Aster – Aster novae-angliae ‘Purple Dome’

Blanket Flower – Gaillardia aristata ‘Burgundy’ & ‘Goblin’

Blue Fescue – Festuca ovina ‘Glauca’

Blue Flax – Linum perenne

Blue Rug Juniper – Juniperus horizontalis ‘Blue Rug’

Blue Star Juniper – Juniperus squamata ‘Blue Star’

Creeping Phlox – Phlox subulata ‘Emerald Blue’ & ‘Snowflake’

Creeping Phlox – Phlox douglasii ‘Cracker Jack’

Caradonna Salvia – Salvia nemerosa ‘Caradonna’

Creeping Thyme – Thymus serphyllum ‘Reiter’ & ‘Pink Chintz’

Coral Beauty Cotoneaster – Cotoneaster dammeri ‘Coral Beauty’

Lavender – Lavandula species

Mexican Feather Grass – Stipa tenacissima

Pink Evening Primrose – Oenothera speciosa ‘Rosea’

Purple Coneflower – Echinacea purpurea

Russian Sage – Perovoskia atriplifolia

Sea Thrift – Armeria maritima ‘Dusseldorf Pride’

Shasta Daisy – Leucanthemum x superbum ‘Snow Cap’

Skyrocket Juniper – Juniperus scopulorum ‘Skyrocket’

Threadleaf Coreopsis – Coreopsis verticillata ‘Moonbeam’ & ‘Zagreb’

Variegated Iris – Iris pallida ‘Variegata’

Special Note: The WSU Master Gardeners partnered with the Kennewick Irrigation District, the Benton Conservation Association, Bedrock Specialty Stone Products, Beaver Bark & Rock, and Irrigation Specialists to create this Low-Water-Use Landscape Demonstration. The local Master Gardeners involved in various parts of the project from planning and planting to weeding and upkeep include Jean Bookwalter, Donna Buechler, Lisa Cash, Dorothy Evans, David Evans, Ellen Meade, Gordon Meade, and Janice Taylor.

Published: 3/19/2008 1:22 PM



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