Xeriscape Demonstration Garden

By Paul F. Warnick, from the March 2003 Newsletter

Most of the city of Moscow's water comes from a deep underground aquifer that has been declining for years. Water usage climbs dramatically during the summer in Moscow as people use water to irrigate lawns and gardens. Because of concerns about future water supplies, the Palouse Basin Aquifer Committee and the City of Moscow were looking for a site to demonstrate the principles of xeriscaping, or low water use landscaping. The City of Moscow provided start-up funding for the garden and the University of Idaho Arboretum & Botanical Garden provided the site, planning, and development.

The Xeriscape Demonstration Garden is located at the south end of the arboretum, just east of the red barn. Convenient parking is available in the lot off Palouse River Drive. The arboretum is open daily with no admission charge. Guided tours can be arranged (with sufficient notice) by calling the arboretum office at (208) 885-6250, or by e-mail. All plants and other assets of the arboretum are provided through donated funds; no tax dollars are spent to purchase the plants, benches, signs, etc. within the arboretum.

Development of the garden began in the fall of 2001, and planting began in May, 2002. The garden is on a fairly steep slope and is divided into four levels. The highest level, located across the gravel road from the main garden site, is devoted to plants native to Idaho. That level is subdivided into two sections: plants from northern Idaho and plants from southern Idaho, divided by a clump of Quaking Aspen (Populus tremuloides) which are native to the entire state. The next level, which is the highest level in the main garden, is planted primarily with woody trees and shrubs, with some ornamental grasses mixed in for textural contrast. The third level is the showiest part of the garden, devoted to flowering perennials, annuals, and grasses. Only this section will require some supplemental irrigation during the driest part of the summer, but still significantly less than an equivalent area of traditional turf or landscaping.

The lowest level of the garden is a demonstration of drought-tolerant turf grasses, with one area of buffalo grass and one area of dwarf, turf-type fescue. We planted the buffalo grass from plugs in June and after it was established in late July, it did not get any irrigation. It was mowed one time to keep it tidy. Buffalo grass grows mostly by surface runners that stay quite low to the ground. It has an interesting blue-gray color that contrasts nicely with the flowers behind it, but it does look quite different from traditional turf. We seeded the fescue in early June and when it was established, it was watered and mowed every two weeks. It is somewhat coarser than traditional turf, but it has a nice green color even with the limited irrigation and seems to be doing very well.

So far, we have planted more than 750 plants in the garden, including 24 species of woody trees and shrubs, 74 types of annual and perennial flowers, and 13 different ornamental grasses. A number of new hybrids and less well-known plants were included in the garden. Although these need to make it through at least one winter to prove themselves, so far several have been very impressive. There are four types of Agastache, sometimes called hummingbird mint, three cultivars of Delosperma (hardy ice plant), two purple flowering salvia, and two ever-blooming hybrid penstemons that have all been particularly impressive. Perhaps the showiest plant of all has been Calyolophus serrulatus 'Prairie Lode', sometimes known as shrubby evening primrose. A low, spreading plant, it was covered with bright yellow, papery flowers all summer long. It reportedly does not like too much water or heavy clay, so it may not do well through a cold wet Palouse winter.

Next in the development of the garden will be the installation of permanent labels and signs so the public can easily identify plants for their own landscapes. There are still some areas to plant and, as with any garden, plants will need to be moved and replaced as they mature. The garden has filled in nicely, and it demonstrates some plants and techniques that can reduce water usage and still give a showy, colorful landscape.

Paul Warnick is a Moscow native who returned to Moscow two years ago to take the position of horticulturist for the U of I Arboretum, where he oversees the maintenance and plantings for the 63 acres of arboretum grounds.

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