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District News Articles


  1. 9/14/2007 NATIVE VS. ADAPTED: WHICH PLANTS ARE BEST FOR WATER-CONSERVING YARDS?
  2. Reprinted with permission of the Colorado WaterWise Council (CWWC)


    There has been a long-standing controversy among landscape aficionados about whether native or adapted plants are really best to conserve water in Colorado landscapes. Looking for a balanced approach, CWWC’s Liz Gardener posed some questions to two are experts, Panyoti Kelaidis, Director of Outreach at Denver Botanic Gardens and Abby Schreiber, Horticulturist and Xeriscape Specialist for Aurora Utilities.

    CWWC: Some people claim that only native plants really belong in a Xeriscape garden, but others claim that both native and adapted plants belong there. What is your experience?

    Panayoti: In the 1970s and 1980s, the National Botanic Gardens of South Africa initiated a campaign to “grow native.” The logic was not just water conservation, but to raise awareness regarding the potential invasiveness of exotic ornamentals, and likely as a promotional campaign. Tens of thousands of native African plants were propagated and disseminated among the enthusiastic public. So many of these plants failed in traditional landscapes, or turned out to look ugly that there was a huge backlash against native plants.

    A large proportion of the most beautiful and drought tolerant plants utilized in Xeriscape gardens originate either in the Mediterranean or South Africa. To deprive our gardens of delospermas, Salvia officinalis, and the many showy spring bulbs like crocuses and tulips would be self defeating. Of course, there are dozens of outstanding natives that look and do wonderfully well in Xeriscapes. In addition, I do believe that native plants are the way to go in semi-rural garden settings, and in revegetated wild sites.

    Abby: As water conservation and specifically drought tolerant landscaping become more mainstream, it is my hope that the public embraces the use of native species for several reasons. Utilizing appropriate natives in the landscape can create a pocket of habitat where our natural landscapes are disappearing. These plants, evolved over thousands of years, are adapted to wild extremes and variations in climate, soil composition, inspect pests, browsers and fire. They flourish without fertilizers and pesticides resulting in less pollution runoff and water use. Finally, more than providing food and habitat, natives help maintain our regional identity and biodiversity.

    CWWC: What further research, if any, needs to be done in this area?

    Panayoti: A great deal of research remains to be done to provide uniform, predicable strains of native plants. Few landscape architects are comfortable specifying plants that could be unpredictable. Our native scrub oak, for example, can produce knee high dwarf forms or towering trees from the same seed sample. If a nursery can guarantee a uniform strain of a native plant, they often find that sales will improve. It would be good to develop a consistent, accepted authority for identifying and distributing uniform clones of native landscape plants.

    Abby: The question I find most interesting is why are we looking away from our natives to find the next best thing across the planet? From what I see in the horticulture industry, there is a large push for plant exploration to find exciting, new ornamentals. What is driving this? Dan Hinckley, formerly of Heronswood Nursery, gave a program recently in Denver. He is one of the premier plant explorers in what I see as the current rebirth of the tradition. I remember him saying his work is controversial. He felt driven to bring back plants, especially from China, where ‘first world’ development was finally catching up to the country and great swathes of native landscape was getting paved over. It was his duty to save these plants before they disappear, a very admirable undertaking.

    How are plants brought back from expeditions in China, Tibet, South Arica, Mongolia and the Middle East tested in our country? What research is done to insure these introductions are not invasive? These plants have been taken out of their environment with their soils, pollinators, browsers, etc. How will they act in this new context? Many escaped imported ornamentals are not on the Colorado Noxious Weed List, including Bouncingbet, Common Tansy, Dalmation Toadflax, Dames Rocket, Mediterranean Sage and Myrtle Spurge.

    CWWC: What do you wish water conservation professionals would tell customers in their presentations and publications about his topic?

    Panayoti: I believe that promoting the use of native and drought-tolerant exotic plants for home landscaping should be the “norm” by water conservation professionals. By seeking out the best examples of artistic, drought adapted Xeriscapes, photographing them stunningly, and preaching their merits, I believe the average Coloradoan’s perception of “clean and green” will shift, and there will be a general adoption of more diverse, more colorful, and more interesting landscapes as being more desirable than hum drum juniper and bluegrass gardens.

    Abby: Water conservation professionals need to educate the public to distinguish between natives and noxious weeds. Natives are useful and attractive in the xeric landscape and generally will not look formal or like an English cottage garden. In fact, if you choose, it may look just a little bit wild. Is that bad? Not all natives are appropriate (aspens should stay at 9,000 feet elevation) and just because an adapted species is drought tolerant does not mean it should be used in our landscapes. Mediterranean Sage is an attractive ornamental, touted as an excellent plant in Xeriscape gardens and yet it is invading Boulder county open space at an alarming rate.

    CWWC: What else should CWWC be asking you about this topic?

    Panayoti: I do not think it’s wise to try and legislate, mandate or force freedom loving Westerners into a native gardening straightjacket. I believe native plants should be encouraged, promoted and loved, but a great deal more research needs to be done on selecting clonal varieties that perform better ad more predictably in landscape settings. There need to be far more in the way of successful models to inspire and encourage the public to adopt native plants on a large scale in their home landscapes.

    Abby: According to professionals and academics that make up the Colorado Weed Management Association, noxious weeds and non-native plants that are disrupting our native vegetation, ecosystems and agriculture. The USDA Forest Service states “invasive, non-native weeds cost the government $137 billion a year in control and mitigation. Each year invasive species advance by 1.7 million acres. Noxious weeds thrive because their natural controls are absent and they are able to adapt to varied climatic conditions.” Some produce 10,000 seeds annually! How do we fight that? I discussed this issue with Irene Shonle, a CSU Cooperative Ext Agent with a PhD in plant ecology. I told her I feel strongly that there should be stringent guidelines to prevent imported, adapted ornamentals from becoming invasive. Her response was that “models aren’t there yet because the plants are so unpredictable. Weed scientists haven’t been able to find the right algorithm, but not for lack of trying.”

    CWWC: Any final, parting thoughts for our readers?

    Panayoti: Water conservation should not be used as a cudgel to force people to use native plants. The carrot to inspire homeowners to grow more native and adapted xeric plants would be that the gardens they create are much healthier for children, animals and grownups than those relying on the life support of toxic chemicals and constant watering. A properly designed Xeriscape can be as trim and neat as the most anal-retentive exotic formal garden, but homeowners should perhaps be persuaded to loosen up and lighten up about Xeriscapes. Learn to love the scruffiness that comes with some experimentation. People can be persuaded, perhaps, that there is great virtue in developing a more colorful, diverse landscape palette for Colorado gardens that gives us an evocative regional identity and saves lots of water in the long run.

    The great bulk of native plant species are best adapted to low water, sun drenched landscape settings. There are far fewer attractive native plants that are available for use in shady gardens. A strict adherence to native gardening will be very difficult for average gardeners. I believe that mix of native and exotic drought tolerant plants is the best common sense solution for home gardening challenges.

    Abby: Perhaps we should be a little more hesitant with new introductions. At the time of this writing I attempted to find the protocols that the Plant Select program undertakes before releasing a plant into the industry. I haven’t given enough time for a response so perhaps we can inform folks in the next issue.