Opportunities and Tricks of Xeriscape

Since the drought of 2002, there has been some real progress in understanding and appreciating xeriscape or water wise landscaping. And yet some people think the drought is over and that we can go back to assuming that we have as much water as we want. But it is quite possible that we could have more droughts, and it would be painful to be as unprepared as we were in 2002. That was our wake-up call. And even with the moister weather in recent years, peoples values are changing. They are more interested in sustainable landscapes, and they want more economical landscapes and gardens that need less water, time, energy and money. And of course that means using plants and methods that are adapted to Colorado conditions.

We live in a semi-arid region that receives about 12—20″ of moisture a year. To have a drought, we only need to miss a few spring snows or rains. If rainfall is below average, or if we have high winds, or if temperatures are higher, as with Global Warming, we will need to use more water. And it is obvious that as our human population rises, water is becoming more scarce and more valuable. In 2005 the Colorado Legislature passed the Colorado Water for the 21st Century Act, and a 2005 Memorandum of Understanding by 32 metro mayors in Denver outlined their commitment to wise use of water in their communities. And Boulder will put its water budgeting program into effect in January 2007. My point is that pressure is coming from many directions to conserve water, and that means it is time to learn to design and to make gardens and landscapes that use less water. It is time for xeriscape to become a mainstream method of landscaping in Colorado.

Since “xeriscape” can mean differing irrigation rates, I am going to use this word to mean a landscape that requires half the irrigation of a bluegrass lawn that is watered conventionally (which is about 25—30″ of water per season), so a xeriscape would need 12—15″ of irrigation per season, or less. I think this is a very generous definition, because I know of some good xeriscapes that are only getting 5—8″ of irrigation per season. Most of the demonstration gardens at my nursery, Harlequin’s Gardens, have been getting 5 waterings a year, or less. But cutting the water use in half is a good goal. Another way of expressing this is to say that a xeriscape should be watered no more than once a week, deeply, or maybe twice a week in July. (After the plants have been established for 6-12 months.)

Xeriscape does limit water use, but does not dictate any style. A xeriscape garden can be formal, naturalistic or highly personalized. It can be mostly ground covers, mostly shrubs, mostly evergreen buns or mostly grasses. It can be mulched with wood chips, rock chips or ground covers.

It is common for people to think of xeriscape as a limitation, but there are opportunities with xeriscape that you don’t get with conventional landscaping. For example, people say “there are plants you can’t grow dry, so you must have a smaller plant palette to work with.” Certainly there are plants you can’t grow in a xeriscape, but there are hundreds of good xeriscape plants that won’t survive in areas with 30″ or more annual rainfall. And these plants can’t survive in conventional Colorado gardens that are watered every day or every other day. Many of our Colorado natives won’t survive moderate irrigation. Big Sage and Apache Plume will rot or look terrible if watered the same as Kentucky Bluegrass, and even “industrial” plants like Snow in Summer, Basket of Gold and most yarrows will grow sloppy and/or develop fungus problems with moderate watering.

Most professionals doing maintenance or landscaping probably know that more plants die from over watering than from under watering. But it is common for people to think that if a little water is good, a lot of water is better. However plants need oxygen just as animals do, and when the soil is saturated with water, the oxygen is driven out. Without oxygen, the plants can’t metabolize properly and the roots can’t grow.

So here are the opportunities with xeriscape:

  1. You can grow many Colorado natives and other dry-loving plants much more successfully.
  2. Non-xeric plants are less vulnerable to death by drowning and they can establish faster because the roots are getting enough oxygen.
  3. You can create a genuinely Colorado or western landscape that reflects and praises the natural beauty of the nature around us.
  4. A xeriscape is more environmentally responsible and more sustainable since it uses so much less of our precious water. It also usually requires little or no fertilization and pesticides. Why? Because xeric plants often come from areas that are naturally lean with little soil fertility, and because if they are given little fertilizer and little water, their tissues are tough and less succulent and therefore less attractive to fungi and insects.
  5. An obvious opportunity and selling point is the fact that people’s water bills will be lower. This factor will become more and more significant as the price of water will continue to rise. In addition, more and more communities will be adopting water budgets, and a low-water landscape makes it easier to stay within your budget.
  6. A xeriscape will survive a drought and water restrictions far better than a conventional landscape. This point would have been much more obvious if the drought of 2002 had been followed by another drought in 2003.
  7. A xeriscape can require less maintenance. In conventional landscapes with ample water and fertilizer, more work is required to cut back plants after flowering, and there are usually more and bigger weeds because many weeds, especially grasses, thrive on ample water. And with less water, there are fewer fungus problems and fewer problems with sucking insects like aphids, which means less maintenance. Even deer are less attracted to dryer plants. (Note that excessive drought stress can increase maintenance problems.)
  8. One of the best opportunities of xeriscape is the winter garden. Unlike English perennial borders and cottage gardens which turn brown and dead-looking in winter, the well-designed xeriscape can be attractive and colorful in winter. The color is not from flowers but from ornamental grasses, and from evergreen foliage that is dark green, gray, silver, blue and many different reds. These rock garden-type plants come from areas, like our own, where the ground is not covered with snow all winter and so they can continue to photosynthesize. A good xeriscape can be very enjoyable to walk through on a warm Colorado winter day. So when you design your xeriscape, don’t miss this opportunity.

In the last issue I discussed the opportunities with xeriscape that you don’t get with conventional landscaping. Now I am going to share some of the tricks that can improve the outcome of a xeriscape garden. The first six tricks are what I call “Water Equivalencies”. Even plants that grow where it’s hot and dry often look better or flower better with some extra moisture, and these tricks will give them extra moisture without increasing irrigation.

  1. Shade equals water. During the 2002 drought, because of water restrictions, a lot of lawns were brown by August, but the areas under trees often were still green. This is a clue that shade equals water. So if you put plants that prefer more water on the east or north side of buildings or fences, they will be protected from all day and hot late afternoon sun. With this shade they will do better with the same amount of water. If you read that a plant needs full sun and you know it is not very drought tolerant, you can often plant it in part shade, because a half day of Colorado sun is usually equal to full sun in the east or midwest.
  2. Planting with rocks equals water. Perhaps this works because with our cool Colorado nights, water condenses and runs under rocks. But whatever the reason, under dry conditions, a plant next to a rock will often thrive or survive while the same plant a foot away may struggle or die.
  3. Soil preparation equals water. Organic matter such as compost or manure holds moisture for longer periods of time, and soil that is loosened and is not compacted permits rain to penetrate and get down to the roots. Compost also is food for mycorrhizae, the beneficial fungi that can extend the reach of plant roots up to 700 times to increase water absorption.
  4. Wind protection equals water, because wind can be so dessicating. Sometimes roses die back in the winter not because of cold, but because wind has dried out the canes, and evergreens are especially vulnerable to drying by wind. A xeriscape garden with a wind break or fence on the west side will require less water.
  5. Mulch equals water, as we know; it keeps the water in the ground from evaporating. And besides organic mulches, fine gravel like squeegee makes a good mulch for penstemons and other rock garden plants that would rot under bark and wood chips. Even ground covers can act as an effective mulch.
  6. Dead-heading equals water. This one is not so obvious, but when a plant goes to seed, it takes a tremendous amount of energy from the mother plant. If a plant is getting little water, it can decline or even die after going to seed. So if you dead head right after flowering and before seed-set, plants will recover much more quickly, and will often live longer.

Here are a few other tricks for xeriscapes.

  1. “Right Plant in the Right Place” is a trick that will improve the outcome of any type of garden. One way to make a garden sustainable is to put each plant in a spot where it is best adapted. I knew a very successful farm manager who told me that everyone who came to him wanted the same thing: “a good farm”. And at first he tried to give them his idea of a good farm with flat, rich ground. But he later learned that what people meant by “a good farm” was one like they grew up on or had worked before, because they knew how to make money on that kind of farm, even if it was hilly and rocky. Plants are like that too, so give them the soil and exposure like where they originated, even if that means hot, lean and dry. Plants that come from cooler conditions will melt in hot locations, so put them in some shade.
  2. Most of you know this, but it is worth mentioning that it is very important to group your plants by water needs. Put the high water plants together and the low water plants together. If you don’t do this, you will have to water all the plants enough to keep the most moisture-loving plants alive. This will waste water, and rot the true xeric plants. I have an area on the east side of my house that I give a little more water and can grow campanulas, foxgloves and gentians that would not survive in the rest of my xeric garden.
  3. Another trick is, if you plant the edges with attractive low-water groundcovers, the entire landscape looks better, even if it has dried out in July. This will be even more true if the ground covers are evergreen and if they have their own drip system.
  4. In a xeriscape you will be able to include tough plants that would be invasive in moderate watering. Plants like Brunnera, Vinca, Hall’s Honeysuckle, Ivy, Sedums, and Sweet Woodruff can be well-behaved and serviceable in a xeriscape. Of course this is a generalization; use it with your own good sense.
  5. The last trick is that for professionals. It is very important to educate clients about what to expect with a xeriscape. People often have unrealistic expectations about a new garden, and sometimes the landscaper has done such a good sales job that they are expecting the Hanging Gardens of Babylon. Tell them the truth: “This is a xeriscape; it may not have as many flowers, but it will have beautiful textures, colors of foliage, beautiful shapes and rhythms. It will support birds and butterflies; it will save water and pest management; and you will be able to enjoy your garden in the winter.” But if all they really want is “masses of flowers all season long”, maybe they shouldn’t have a xeriscape, and it’s better to know this upfront.

There are drawbacks to xeriscape which should be admitted, but there are ways to reduce their impacts. In a xeriscape there are certain plants you won’t be able to grow, like astilbes, hostas, ferns, many campanulas and Hybrid Tea roses. How to reduce the impact? Select a small, high visibility area in a protected location like on the north or east side of the house or other structure, and group your high water plants there, and give them more water. This is still xeriscape and water wise. Or, plant other plants that are similar-looking but use little water. For example: instead of hostas, use Lady’s Mantle or Bergenia; instead of ferns use Sweet Cecily or yarrows; instead of Hybrid Tea roses, use Shrub Roses on their own roots; instead of New England Asters use western native asters.

Another disadvantage to xeriscape is that plants that are watered sparingly won’t fill in as fast as plants that are given ample water. To reduce the impact, water amply (but not excessively) the first year to get faster fill-in, then reduce the watering the following year, or mulch to cover bare areas. Also low-water annuals can be planted to fill in the gaps for a year or two.

Xeriscapes also generally bloom less than landscapes given ample water. Now I’m sure that Lauren Springer and Marcia Tatroe and some other very experienced designers could get a xeriscape to bloom as much as a conventional landscape. But this is not easy and, in my opinion, the state of the xeriscape art isn’t there yet. So to reduce the drawback of fewer flowers, water more during the blooming season to get more flowers, then cut back after blooming, or plant self-sowing xeric annuals to get masses of color for 6-8 week periods. And you can plant large flowering shrubs and tough roses for big splashes of color. Also, fewer flowers will not be noticed in a garden that is designed for sculptural forms, textures, foliage colors, variety of bloom times, for wildlife or for peaceful and meditative qualities.

Another disadvantage is that xeriscapes can look burned out and scruffy in July and August. In nature in Colorado, this is normal and not a problem as long as the plants can reproduce and/or come back strong the next year. But most home-owners and neighbors don’t like scruffy gardens. So what is the antidote? In early July, do a good maintenance of dead heading, weeding and cleanup, followed by the longest, deepest watering of the year. This will give the garden a pick-up, new growth will be supported, and blooming will be encouraged for the summer and fall bloomers.

In Colorado we are looking for our own genuine landscape style. Traditionally, American gardens have been influenced by the English and Japanese styles, but both of these are more successful where there is ample moisture and temperatures are not too severe, like on the east and west coasts. Here in Colorado, we have to discover a more appropriate style, using plants that are water-wise and cold hardy, like western natives and plants from similar regions around the world. And we need to apply methods that are adapted to Colorado conditions.

Beyond these guidelines, follow your own muse. Those of us who have been the leaders of the xeriscape movement for the past 20 to 25 years will be looking to you for the innovations and solutions in the next 25 years of Colorado regional design. No magazine article is as powerful as the examples of our (your) own gardens in showing others that resourceful, ecological and water wise gardens can be beautiful and wonderful.