Drought-tolerant plants

Although our weather may now be entering an afternoon rain pattern, the past several weeks of very hot and dry weather have wreaked havoc on most of our gardens. If your garden looks a bit worn and wilted at this point in the growing season, you may find my five-year-old experimental "no water" garden to be of interest.

In 2002, Colorado's worst drought year in 40 years, I set aside approximately 1,000 square feet on a south-facing slope as a garden area which would receive no supplemental water.

My "no water" garden came about out of necessity. The area was still scarred from our home's construction and sorely needed beautification, but my gardens had already grown beyond the capacity of our well, the time and energy I had to devote to the care of my gardens, and my budget.

Moreover, although my existing gardens contained mostly xeric natives and ornamentals and I watered sparingly, using water to pursue my gardening hobby was beginning to weigh heavily on my conscience.

Besides being south-facing, the area designated to be my "no water" experiment had no shade and was bordered by my stucco and rock house, sandstone patios and gravel walkway all which serve to reflect heat into this area. Large granite boulders are scattered throughout. The area was truly a large "inferno strip" where I knew only the most drought- tolerant and heat-loving plants would survive.

My experiment went beyond "no water." It has become largely "no cost" and "no maintenance." I pull an occasional noxious weed, but do little else in the way of care. I have also spent next to nothing on this rather large area. Most of the plants are been grown from seed or have come from cuttings and transplants from other garden areas. Shrubs were purchased in the inexpensive bare root bundles sold by 4H each spring. I have not amended the soil or provided any mulch other than that created by naturally decaying plant matter.

While this garden area will not win any landscape design awards and plants tend to be a bit smaller than those of the same species growing in my gardens which receive supplemental water, many species have survived and even thrived.

The success of this "no-water garden" relied largely on discovering what species can survive with low moisture levels. Generally, species that have small leaves, blue or gray foliage and root structures designed to store water have a greater chance for success.

Planting at the correct depth is also important. Plants placed too high will be exposed to low humidity, desiccating winds and fluctuating air temperatures. Too low, they cannot get oxygen, especially in heavy soils.

Using rocks, walls or other structures to shade the roots and trap moisture in the soil will generally benefit the plants. However, heat generating off structures and rocks may also be damaging. I do take the time to wander through this garden to see how plants are faring and occasionally move a plant to another garden where it will receive more attention and care.

Mulching is a good idea. Mulch helps to retain water and protect the plant from temperature extremes, wind and freeze/thaw. Although I have not mulched my "no water garden, I may add pea gravel in the future.

Amending the soil would most likely increase the success rate in my garden and result in larger plants and more blooms. Amending the soil increases nutrients and provides for better water retention. Since the majority of the plants I have planted are natives, I am comfortable with my decision not to amend the decomposed granite soil in this particular area.

Even if you are not prepared to completely turn your garden over to the elements, knowing which plants have survived in my garden may help you to select plants which will have a high success rate during periods of intense heat and drought.

Survivors in my No-Water Garden 2002-2007

Achillea millefolum (White Yarrow)
Achillea filipendulina (Moonshine Yarrow)
Artemisia frigida (Fringe Sage)
Callirhoe involucrata (Poppy Mallow)
Campanula rotundifolia (Harebell)
Chrysothamnus nauseosus (Rabbitbush)
Erigonum umbellatum (Sulphur Buckwheat)
Erysimum asperum (Western Wallflower)
Eschscholia california (California Poppy)
Falugia paradoxa (Apache Plume)
Gaillardia artistata (Perennial Blanketflower)
Gaillardia pulchella (Annual Blanketflower)
Lavandula angustifolia (English Lavender)
Linum lewisii (Blue Flax)
Lupinus argenteus (Silver Lupine)
Mirablis multiflora (Colorado Four O'Clock)
Nepeta faassenii (Blue Catmint)
Nepeta faasenii 'walker's low' (Walker's Low Catmint)
Penstemon strictus (Rocky Mt. Penstemon)
Perovskia atriplicifolia (Russian Sage)
Potentilla fruticosa (Potentilla)
Ratibida columnifera (Mexican Hat)
Rosa woodsi (Native Rose)
Stanleya pinnata (Prince's Plume)
Viguiera multiflora (Showy Goldeneye)
Zinnia grandiflora (Prairie Zinnia)

In addition to the plants in my garden, the Cheyenne Mountain Zoo in Colorado Springs provides a list of species which have survived in their "no water" garden on their website at www.cmzoo.org.

Other good sources for xeric gardening information are Denver Botanic Gardens www.botanicgardens.org and Colorado State University www.ext.colostate.edu. For information on native plants, are usually the best choice for no water and low water gardens, go to the Colorado Native Plant Society website at conps.org.

Nan Spence has certification in Rocky Mountain Gardening through the Denver Botanic Gardens and is a Native Plant Master with Jefferson and Gilpin Counties.