water wise plants

Save water by choosing your plants wisely

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In Pullman:
Xeriscape Demonstration Garden, Lawson Gardens.

The City of Pullman asks: How can you reduce irrigation in order to conserve water and save on your water rates?  One tip is to carefully consider what you plant.  At Lawson Gardens we have a xeriscape garden that features a wide variety of drought tolerant plants that thrive in our region.  Just follow the path up the hill at the west end of the Lawson Garden parking lot to discover how you can obtain a lush ground cover without consuming large amounts of irrigation water. For a list of appropriate plants, see the Xeriscape Brochure: PDF

In Moscow:
Xeriscape Demonstration Garden, University of Idaho Arboretum

Walking in the University of Idaho Xeriscape Garden

The Xeriscape Demonstration Garden  shows how plants can thrive in our region with little or no watering. The garden located at the south end of the UI Arboretum, 1200 West Palouse River Drive, Moscow, Idaho, just east of the red barn. The arboretum is open seven days a week, with no admission charge. Because many of the plants in the garden have interesting and attractive foliage that persists through the fall and winter, the garden should be visited in all seasons. Plants are labeled to assist visitors in choosing plants for their own landscapes. For a plant inventory, click here. Guided tours can be arranged by contacting Paul Warnick, the arboretum horticulturalist, at pwarnick@uidaho.edu or 208-885-5978.


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Following are Paul’s excerpts from Arbor Notes: A Newsletter of the Arboretum Associates that describe the development of the xeriscape garden.
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August 1, 2008

The Xeriscape Garden is in its seventh growing season.  We try new plants every year, and as with most any garden we have had some success and some failures.  Probably the most common failures tend to be the truly xeric plants such as the hardy agaves, some of the cacti and the hardy ice plants (Delosperma).  All of these plants require good drainage and they don’t cope well with our gray, wet winter weather.  The most visible success has been the patch of ‘Triple Crown’ Turf Type Fescue.  It has maintained a rich green color throughout the summers with only very minimal watering.  Usually we have watered it 2-3 times each summer; but so far (July 30th) we have not watered it at all in 2008.

We did make a major addition to the garden this spring.  One of the concepts of xeriscaping is the idea of using native plants since they will be adapted to the local climate.  We used a number of natives throughout the garden.  Then I wanted to have a section devoted strictly to plants native to Idaho.  This section is on the bank across the gravel road from the main garden.  It is divided into two areas, from the grove of quaking aspen north is devoted to plants native to Northern Idaho; while from the grove south is devoted to plants native to Southern Idaho.  I planted commercially grown woody plants (except for the aspen which came from Moscow Mountain) in 2002 in both sections.  I decided to try to restrict the rest of the plants to plants actually grown from seed collected in the wild in Idaho, to make them truly natives.  It has been fairly easy to get wildflowers and grasses from local sources, so there is beginning to be a nice selection of Palouse Prairie natives.  However, it has been much more difficult to get plants started from Southern Idaho.  This year I was able to collaborate with Steve Love a U of I extension agent in Aberdeen, Idaho.  One of his research focuses is to look into using native plants for ornamental purposes.  He has been collecting several things from Southern Idaho and agreed to provide some for the xeriscape garden.  He gave us twenty wildflowers that were all grown from seed collected from Southern Idaho sources.  Also, last summer I was able to work with the Idaho Botanical Garden in Boise which has some McFarlane’s Four O’Clock growing in their garden.  McFarlane’s Four O’Clock is a showy wildflower from Southern Idaho which is on the federal list of threatened or endangered plants.  The Idaho Botanic Garden gave me some seeds last summer and I was able to get several to sprout and grow this spring.  With both of these additions we will begin to see more color and species diversity in the Southern Idaho section of the garden.

We have also started another educational project.  Since xeriscaping is simply a method of landscaping that requires less water than traditional landscapes I want to be able to track exactly how much water we do use.  So far this year the only supplemental watering we have done is hand watering with a hose, mostly the newly planted plants, along with some watering of the central perennial bed.  We are installing a drip irrigation system on the central perennial bed; and installing a separate hose faucet that will be only be used in the xeriscape garden.  We will also install a meter on that line, so that we can track exactly how much water we actually use.  Assuming that the system works, next year I will try to track the usage monthly during the irrigation season, and post that information on the arboretum Web site.

I will also try to translate the gallons per month that the meter will track into a dollar amount if we were using water from the Moscow water system.  I hope that will demonstrate that it is possible to garden in the Moscow area using a minimal amount of water.
Arbor Notes, April 2003

Xeriscape Plant Profile: Artemisia

The genus Artemisia is named for Artemis, the Greek goddess of the moon. Many of the plants in the genus have soft, silvery foliage which glistens in moonlight.

There are currently seven different types of Artemisia growing in the xeriscape demonstration garden. Probably the best known Artemisia is Sagebrush, Artemisia tridentata. Most people don’t think of Sagebrush as an ornamental, partly because it is so common and partly because if it is left to grow without any pruning, it quickly tends to get open and ‘scraggly’. However, it can be a very useful plant if it is treated correctly. Its first requirement is that it needs full sun and does not thrive on excessive water. That can be a particular problem in the heavy soils around Moscow. It grows best on a south facing slope, with little or no irrigation once it is established. Another requirement is that it looks best if it is pruned rather severely at least once a year, especially if it is getting any additional irrigation. Its silvery gray, aromatic foliage is mostly evergreen, and anyone who loves the wide open spaces of the West has to love the smell of the foliage. It can easily be maintained as a three to four foot tall shrub, which looks especially effective against a darker background.

The rest of the Artemisias growing in the xeriscape garden are all more or less herbaceous, this is they will die back to the ground each winter and start afresh each spring. They thrive in the same conditions as sagebrush, full sun and not much water. If they are given too much water they tend to get leggy and flop over. If that happens a quick cutting back will solve the problem, and they will quickly grow back.

In order of their eventual size, the other types of Artemisias currently growing in the xeriscape garden are:

Artemisia ‘Powis Castle’ – a hybrid of two European species of Artemisia. This one is almost a woody shrub, growing 2-3′ tall and 3-4′ wide. Soft, silvery foliage makes a great contrast with any darker colors. It will tolerate virtually any pruning, but should definitely be cut back hard in early spring. This is the least cold-hardy of all of the Artemisias in the garden, with some sources listing it as only hardy to zone 7 (0-+10 degrees), but so far it has wintered fine for us.

Artemisia ‘Oriental Limelight’ – a variegated form, with striking bright yellow and green foliage. It grows 2-3′ tall and wide but can spread by underground stems. It grows fast enough to be useful in containers or annual plantings.

Artemisia frigida
is another native species of sage, but this one is completely herbaceous, dying back to the ground each winter. Like all of the types we have in the xeriscape garden, this Artemisia’s flowers are unimpressive, it is the foliage that makes the show, so when flowers appear it is best to remove them.

Artemisia schmidtianaSilver Mound’ is an old perennial cultivar which deserves to be planted in every garden. It grows in a soft mound, 6″ tall by 2′ wide, with incredibly soft, silvery foliage which just begs to be touched. As an added bonus, it is almost as fragrant as sagebrush.

Artemisia versicolor
‘Sea Foam’ is a new cultivar introduced from England, is similar to ‘Silver Mound’ but much more textural. The branches grow out in twisted curls, instead of the uniform mound of ‘Silver Mound’. Like all these Artemisias, avoid extra water and fertilizer once the plant is established.

Artemisia viridis (Tiny Green) is a mat-forming groundcover of fine textured foliage, but, unlike the other Artemisias we grow, this one has green foliage.

From Arbor Notes, December 2003

The xeriscape garden that was started last year has filled in very nicely and actually has taken less time than anticipated to maintain. The garden has two turf areas, one of Buffalo grass and the other a blend of Turf Type Tall Fescue. We did not water the Buffalo grass at all this summer and only mowed it twice. It filled in nicely, but I don’t think most people will accept it as a substitute for a traditional lawn, due to its bluish gray color and relatively short growing season. It is a warm season grass which didn’t really show growth here until early June and it stopped growing and turned golden in mid-September. However, so far the Fescue looks like an excellent alternative to traditional blue grass lawns in our area. It has been a beautiful, rich green color virtually all year. We only mowed it every two weeks and only watered it three times all summer, starting in mid July. An important consideration is to mow this grass at a high setting, at least three inches tall. The increased size of the grass allows it to shade the soil somewhat and gives it more strength to recover from mowing. Virtually any of the traditional cool season turf grasses benefit from an increased mowing height, especially in the heat of the summer. One major potential disadvantage of the Fescue grass is that it is rhizomatous (that is, it does not spread by roots). So, if patches die out they won’t fill in readily by themselves, they will need to be reseeded. Fortunately that has not been an issue for us yet, but it probably would be in most home situations. We added quite a few new plants to the garden this year, and those were hand watered regularly, but the areas that were established last year were only watered twice all summer. So, I think the xeriscape idea shows real potential for reducing water use over more traditional landscape designs. The garden has filled in nicely and has a display of flowers all season long.

From Arbor Notes, December 2002

Most of the city of Moscow’s water comes from a deep underground aquifer which 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 arboretum staff provided planning and development. Through some of the very generous donations we were able to match the city’s funding for plants and materials. The garden is located at the south end of the arboretum, just east of the red barn.

Development began last fall, with herbicide treatments on the site, grading, and installation of rocks and boulders. After another herbicide application this spring, planting began in May. The garden is on a fairly steep slope and is divided into four levels. The highest level, which is across the gravel road from the main garden site, is devoted to plants native to Idaho. That level is further divided into two sections: plants from northern Idaho and plants from southern Idaho, divided by a clump of Quaking Aspens (Populus tremuloides) which are native to the entire state. This part of the garden will have a more natural, less manicured look than the rest of the garden. Once established, this level should need little or no irrigation. The next level, which is the highest level in the main garden, is planted primarily with woody trees and shrubs, with ornamental grasses mixed in for textural contrast. Again, once established, this level should require little or no irrigation. The third level, the showiest part of the garden, is devoted to flowering perennials, annuals, and grasses. It will require supplemental irrigation during the driest part of the summer, but significantly less than an equivalent area of traditional turf and landscaping. The lowest level of the garden is a demonstration of drought-tolerant turf grasses. It includes an area of buffalo grass and an area of dwarf turf-type fescues. 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 very different from traditional turf.

We seeded the fescues in early June and, when established, it was watered and mowed every two weeks. It is somewhat coarser than traditional turf, but it has a bright green color, even with the limited irrigation, and it grows very well.

So far, we have planted more than 750 plants in the garden. These include 24 species of woody trees and shrubs, 74 types of annual and perennial flowers, and 13 different ornamental grasses. Many plants are traditional favorites like California poppies, purple cone-flowers, artemisias, thymes, and sedums. A number of new hybrids and less well-known plants were included in the garden. Although these need to survive 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. It grows as a low spreading plant which is covered with bright yellow, papery flowers all summer. It reportedly does not thrive with too much water or in heavy clay soil, so it may not survive a cold, wet Palouse winter.

The next step in the development of the garden is to install 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 plants and techniques that can reduce water usage and still provide a showy, colorful landscape.

From Arbor Notes, December 2001

We have began work on two larger construction projects – a new xeriscape demonstration garden and five new small ponds along the stream. In August we drew plans and began grading and marking out the beds for the xeriscape demonstration garden at the south end of the arboretum. In early November we started placing large moss-covered basalt boulders within the beds. We are working with the City of Moscow Water Department to demonstrate that there are many attractive plants that will thrive in this area with less water than a traditional blue grass lawn.

From Arbor Notes, April 2001

The arboretum staff has been working with the Palouse Basin Aquifer Committee and the City of Moscow Water Department to obtain funding to develop a new xeriscape demonstration garden. Xeriscaping is a term coined in 1981 by an employee of the Denver Water Department to describe the concept of using plants and other landscaping elements that require less water than traditional landscaping. The Arboretum Master Plan that was adopted in 1980 calls for developing display gardens in the southern portion of the Arboretum consisting of collections of various types of plants. Developing those display beds and collections is the next phase in the development of the Arboretum. The xeriscape demonstration garden will be a good starting point for these gardens and it should become a valuable educational tool for the citizens of Moscow and the surrounding area.

The groundwater in the Palouse Basin Aquifer, which supplies most of the water for Moscow, Pullman and the surrounding area, has been declining at an alarming rate for several years. If it continues to drop something will have to be done, either importing water from long distances or drastic rationing will be required. During the summer months water usage nearly doubles in the area due to irrigation of residential and commercial landscapes. So, if attractive landscaping can be designed which requires significantly less water than traditional landscaping, it could make a profound difference in the water usage on the Palouse.

Xeriscaping consists of seven basic fundamentals:

  1. Plan and design comprehensively from the beginning
  2. Create practical turf areas of manageable sizes, shapes, and appropriate grasses
  3. Use appropriate plants and zone the landscape according to the needs of the plants
  4. Consider improving the soil with organic matter like compost or manure
  5. Consider using mulches, such as wood chips
  6. Irrigate efficiently with properly designed systems (including hose-end equipment) and by applying the right amount of water at the right time
  7. Maintain the landscape appropriately by mowing, pruning and fertilizing properly

From: Knopf, Jim. 1991. The Xeriscape Flower Gardener: A Waterwise Guide for the Rocky Mountain Region. Boulder: Johnson Books.

As you can see from these fundamentals, xeriscaping is not limited to strictly dry landscaping, nor does it advocate the elimination of lawns. Rather, it encourages using smaller areas of turf with alternative types of grasses, along with specific ornamental plants selected for their ability to thrive with less irrigation.

The concept for the xeriscape garden calls for meandering pathways of different types of grasses, winding between beds of various shapes and sizes, designed to show off the wide variety of plants that will thrive with less water than typical landscaping. These will include lots of colorful perennial flowers along with various trees and shrubs. Some large boulders and other rocks will be included in the design to add an instant sense of permanence to the garden. Various types of mulches available in the area will be incorporated in the design to demonstrate how they can be used attractively. As funding allows and as the beds mature some types of drip irrigation systems may be added to complete the project.