by Matt Corrion
By now most people in the western U.S. are familiar enough with Xeriscape to know that there is indeed no “zero” in the pronunciation (it’s pronounced more like zeer-escape). The term 
was coined by the Denver Water Department in 1981, are derived from the Greek word “xeros”, meaning dry.
There are 7 principles that make up the concept of Xeriscape: planning and design, improving the soil, creating practical turf areas, irrigating efficiently, proper plant selection, using mulch, and maintaining the landscape.
While I am not sure EXACTLY when the 7 principles were first released (my guess is a few years after the term Xeriscape was first used), I have often wondered whether an update was needed, or if the same 7 principles would be adopted exactly the same today.
While today Xeriscape remains as relevant as ever, there are some important observations I have made through experience regarding the 7 principles, common misconceptions about them, and how they relate to landscaping in today’s rapidly changing world. Therefore, I thought it might be helpful to revisit and add updates to the original 7 principles:
Principle #1: Planning & Design
Updates: Planning and design is as important today as ever. Landscapes continue to get more complex as dozens of new plant choices are introduced each year, along with advances in irrigation systems and controllers. The more complex a project gets, the more benefit is gained from careful planning and design.
Another important development has been the landscape architecture license act of 2007, when Colorado joined the rest of the country in requiring that landscape architects be licensed, and that all commercial and large residential projects (greater than 4 units) have landscape plans that have been prepared by a licensed landscape architect. While this may have raised the cost of design somewhat, a good efficient design will always pay for itself by minimizing surprises during construction, allowing plans to be competitively bid, and lowering maintenance costs over time.
Misconceptions: Xeriscape can only be done in one style. A design will make the project cost more.
Principle #2: Soil Improvements
Updates: This is one area that needs to be looked at closer. The intention of this principle should be to “analyze and improve soil when needed, depending on what plantings are proposed”. The problem has been that many cities and municipalities started to require that all landscaped areas have large amounts of amendment incorporated into the soil over the entire landscaped area, and even requiring dump tickets from the contractors to prove that the amendments were placed.
While this is a good idea for bluegrass and for some types of plants, there are many other plants were the amendment is detrimental to plant health. Many of the very xeric and native plants prefer the native, rockier soil, and can suffer from root rot if soil is heavily amended with organics. I personally think that the amendment should only be tilled into new bluegrass areas, and in the individual planting backfill of those plants that will benefit from it.
Misconceptions: All plants require soil improvements.
Principle #3: Practical Turf Areas
Updates: I am not sure whether the original principle read “Practical Turf Areas” or “Practical Bluegrass Sod Areas”. One of the trends I am seeing that we are starting to use in our designs is the creation of “turf” areas from groundcovers and/or spreading perennials and shrubs. The questions that one needs to ask is not only where will the lawn areas be, but does an area really need to be a “lawn” at all?
Many of the bluegrass turf alternatives are very difficult and sometimes expensive to get established. If an area of the landscape will not be used for games and high foot traffic, then why substitute a hard-to-grow lawn alternative for bluegrass when there are many good spreading plants that are easy to grow? In other words, if a “turf” area will not be used, it simply becomes a low growing visual element, in which case many planting alternatives should be explored.
Misconceptions: Xeriscape means no grass, and bluegrass turf cannot be used in a Xeriscape.
Principle #4: Efficient Irrigation
Updates: Many advancements in irrigation have been made in the past several years, making it possible to irrigate even more efficiently. However, many of these benefits have been over-hyped. While I am all for making our irrigation systems more efficient, this approach does not address the underlying issue- how much water does my landscape REQUIRE to remain healthy? Only by installing water efficient landscapes will any major impact be made.
Misconceptions: If one installs new irrigation heads and a smart controller, the amount of water they will need to use will go down significantly.
Principle #5: Proper Plant Selection
Updates: This principle goes hand-in-hand with a good design. One of the overlooked aspects of this principle is a phenomenon known as “micro-climates”. Microclimates are small climate differences that occur in the landscape due to sun vs. shade relationships, water availability and retention, wind, soil differences, etc. Every day in this business I am reminded how plant selection is impacted by these micro-climates.
One area of debate is the natives vs. non-natives argument. I am firmly in the non-natives camp. There are some amazing native plants that I love to use, but there are also many non-natives discovered every year that meet the needs of our varying miro-climates.
Misconceptions: Only native plants are appropriate to use.
Principle #6: Mulching
Updates: The biggest problem I see with this principle is that all mulches are not created equal. There are cost, aesthetic, and weight differences between wood mulch and rock mulch. Not all plants like being heavily mulched, and some prefer rock mulch over wood mulch, for many of the same reasons some plants do not like a lot of soil amendment. As a result, wood mulch seems to be getting a bad name for Xeriscapes. I have even seen some cities write into code that wood mulch cannot be used for a low water-use zone. But wood is often quite a bit less expensive than rock mulch, and is WAY easier to move around, plant in, and make adjustment to than rock.
The bottom line on mulching- there are different rules to follow based on the type of mulch you are using. If you use wood mulch, use a thin layer and be sure not to over-water. If you use rock, remember that it will be difficult to add plants later or make changes to rocked areas. Also, keep in mid the aesthetics- I feel that too much rock can make a landscape seem a little too harsh, and but having a combination of mulch types can help to visually break up large areas.
Misconceptions: All mulch is the same, all plants love being mulched.
Principle #7: Maintenance
Updates: This is the most undervalued principle. For every 10 beautiful landscapes that I have designed and enjoy visiting time and again, there is at least one commercial landscape where even the most basic maintenance has been neglected. Shrubs have been sheared off into little balls right before they were about to flower, weeds have overtaken a bed area, plants have been over-watered to death.
The biggest piece of advice I can give to property owners or managers is this: walk your landscape once in a while, and make maintenance adjustments based on what you see. Remember that plants are living things, and your job is to understand what will allow each plant to flourish naturally, with the least amount of interference (such as over-watering, over-pruning, etc.) while at the same time minimizing negative factors such as pests, weeds, etc.
Misconceptions: All plants like more water, all shrubs need to be pruned, all plants have similar needs.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Matt Corrion
Evergreens are important Xeriscape plants for Colorado landscapes. Since lawn areas are often limited in Xeriscaping design, evergreen plants can step right in to provide rich green color all year long.
Evergreen plants also provide great contrast with other plants, particularly with the the foliage and seed heads of ornamental grasses, and as a backdrop for flowering shrubs and perennials. And evergreens can often be utilized to effectively create privacy and screen or block undesirable views in the landscape.
I am limiting this top 10 list to evergreen shrubs. Another very interesting category of plants are the so called “semi-evergreens”, which are deciduous plants that keep all or part of their foliage throughout the winter. I will do a future list of the top semi-evergreen Xeriscape plants. I am also excluding large trees from this list, as they are a category unto themselves and many people are already familiar with evergreen tree choices.
Although this is a Colorado list, most of these plants can be used in many places throughout the world depending on the local climate.
- Panchito Manzanita – Arctostaphylos x coloradoensis ‘Panchito’ Panchito Manzanita is a low growing woody shrub with shiny, oval, dark green leaves that persist throughout the winter. It gets small, pale pink flowers followed by small red berries- but it’s best characteristics are the evergreen foliage and the fact that it requires little care or water. The only time I have had an issue with this plant was when it was placed in an area with very poor soil and poor drainage- even then, the plant looked healthy, it just didn’t get any larger.
- Kinnickinnick – Arctostaphylos uva-ursi Since the Mock Bearberry and Panchito Manzanitas have become some of my favorite plants, I started taking a second look at their cousin the Kinnickinnick. This plant has been around for a long time and thrives in the eastern U.S. Here in Colorado, it needs full to partial shade and requires a little more water. It stays a little smaller than the other Manzanitas, but since there are so few evergreens that thrive in shade it is an invaluable plant.
- Oregon Grape Holly – Mahonia aquifolium I consider Oregon Grape Holly to be an evergreen plant, even though that may not be botanically correct. It has large, glossy leaves that persist through winter, turning bronze-red, and gets clusters of small yellow flowers in the spring. It can handle a ton of different conditions, from partial sun, through full shade, and doesn’t seem to mind the toughest clay soil. This plant is a true staple of the Colorado Xeriscape. Oregon Grape Holly gets about 4-6 feet wide and tall, with the “compacta” variety staying about half of that size.
- Yucca – Yucca ssp. Native to the Southwestern United States and Mexico, Yuccas are another plant that is not generally thought of as an evergreen. But they are just about the perfect evergreen plant for a Xeriscape! Yuccas provide really good steady green foliage that can blend in with other plants or be used as a statement with it’s unique form. A tall stalk of white flowers appears in summer to make these plants all the more interesting. All that, from plant that is native to Colorado and requires no maintenance or no supplemental watering! Note: Red Yucca is another great plant that gets red flowers instead of white. It’s scientific name is Hesperaloe parviflora.
- Agave – Agave parryi Agaves are very similar to Yuccas, and provide many of the same benefits. They tend to grow slower, and are a little smaller, so I recommend using them closer to pathways so their foliage can be enjoyed. Agaves only flower once every 25 years, sending up a very tall flower stalk. After they flower, the parent plant dies, and is replaced bu suckers from the root.
- Dwarf Globe Blue Spruce – Picea pungens ‘Glauca Globosa’ Most people would not consider this a true Xeriscape plant, but I am including it because I have had very good luck with these plants in Xeriscapes. Being a spruce, they do require a little more watering until they are established. However I have seen these plants used in low water use landscaped on the same drip zone as true Xeriscape plants and they have thrived. The blue color and the fact that they stall relatively compact are characteristics that cannot be found with any other plants that I am aware of.
- Mugo Pine – Pinus mugo ssp. Mugo pines can provide very good dark green color, and are perfectly adapted to Colorado’s climate. They are a perfect accent to boulders and flowering perennials. Be sure to give them plenty of room, they are slow growing and are usually pretty small at the time of planting- however most of the varieties will get quite large over time.
- Spreading Junipers – Juniperus horizontalis ssp. Junipers have been given a bad name, as we have written about before, but creeping or spreading junipers require little maintenance and can be very valuable parts of a well designed Xeriscape. These plants work well when mixed with a variety of flowering and deciduous plants and grasses. They can provide good ground coverage and green color to break up large mulch areas and as understory between shrubs. Varieties such as “Youngstown” and “Blue Chip” offer a variety of green to blue-green hues.
- Upright Junipers – Juniperus scopulorum ssp. These upright shrubs can work well as vertical elements in a Xeriscape (as seen above), or to provide screening of utility areas. Some of the varieties stay very narrow, which can be invaluable in tight spaces where evergreen trees would get far too wide. Be wary of limb breakage in very heavy snows, especially with very narrow varieties such as “Skyrocket”. Junipers are native to Colorado and require very little water, care, or maintenance.
- Compact Tanyosho Pine – Pinus densiflora ‘Globosa’ Compact Tanyosho Pine is a unique large shrub or small tree that has a very nice dark green color and requires minimal maintenance. It is one of the rare evergreen trees that stays very compact, yet requires little water unlike many of the other dwarf conifers. It also has an interesting form, with one or multiple bare trunks at the base with the needles forming a mound at the top.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Matt Corrion
On January 25th, the U.S. Department of Agriculture (USDA) released an updated version of their Plant Hardiness Zone Map. Here are some excerpts from the USDA website, where you can also view and download the new maps:
The 2012 USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones.
For the first time, the map is available as an interactive GIS-based map, for which a broadband Internet connection is recommended, and as static images for those with slower Internet access. Users may also simply type in a ZIP Code and find the hardiness zone for that area.
No posters of the USDA Plant Hardiness Zone Map have been printed. But state, regional, and national images of the map can be downloaded and printed in a variety of sizes and resolutions.
My thoughts: It is kind of surprising that the maps have not been updated since 1990.
You can enter your zip code, search by state, or simply click on your state on the national map to get a new state map.
Colorado, like most places, got a little warmer. Now Zone 3 only includes areas at high elevations. The foothills are a mix of Zone 4 and 5, and the urban “heat island effect” is taken into consideration with Denver in Zone 6. What changes are you seeing for your area?
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Matt Corrion
Ornamental grasses are more popular than ever, and for good reason. They can add texture to the landscape, and they are tough plants that are easy to grow in a variety of conditions. 
Ornamental grasses can also add beauty to the winter landscape.
But should ornamental grasses be cut back to the ground in winter?
Most ornamental grasses develop tall seed heads late in the summer that naturally persist through the winter. When temperatures start to drop the plant will die back, leaving the dried foliage, stalks, and seed heads. The general rule that you should cut back the grasses before the next growing season, so that the new year’s growth will be more vigorous and healthy.
I have found a couple of exceptions to this here in the Denver area, particularly with Mexican Feather Grass (Nassella tenuissima), which did not regenerate as well or look as good the year after I cut it back. I have since started leaving it uncut, which results is the new growth coming up right through the beautiful finely textured golden old growth. But with most varieties, they should be cut back before new growth starts in the spring.
So the question, then, is whether you should cut them back in the fall, or wait until the spring. Many people enjoy the colors and movement that these elements provide in winter. Others prefer a more “neat” or formal look.
I thought it would be interesting to explore the advantages each approach:
Advantages of leaving the grasses for the winter and waiting until the spring to cut them back
- When shrubs lose their leaves, and perennials wither to the ground, grasses can provide form in the landscape
- Texture: Interesting textures can stand out, collecting frost or snow, and reflecting sunlight
- Movement: Winter winds and soft breezes can move and sway the stems and seed heads of ornamental grasses
- The grasses can add color to the drab winter landscape, including shades of reds, yellows, browns, and blues
- Upright grasses can be used to help screen views when deciduous plants have lost their leaves
- The grasses can provide habitat and shelter for birds and other small animals
Advantages of cutting back ornamental grasses right away in the fall or early winter
- This can be interesting and different look, I have seen some nice formal plantings that looked stunning with the grasses cut back
- Some grasses hold their form better than others, while some varieties may flop over under heavy snow
- Cutting them back may give the impression (rightly or wrongly) that a commercial landscape is being better maintained
- In some cases the grasses may block sight lines, such as to important signage in a shopping center
- In high foot traffic areas, it may be beneficial to cut back ornamental grasses to avoid them being trampled
So what do you think, is one method better than the other? My personal taste is to leave the grasses up all winter, but there are situations where you may want to cut them back. And you can always decide to cut them back later, if you feel the need to tidy them up.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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