Written by: David W. Sams, Colorado Master Gardener – Apprentice, 2024

My wife and I moved to Colorado early in 2021. We grew up gardening in Western Washington State and gardened in Minnesota and Morocco before spending 42 years gardening in Tennessee. We were avid gardeners and believed that we would soon have a lush new garden. We soon found out that we were unprepared for the unique challenges of Colorado gardening. Now, three years later, we would like to share some of the challenges we encountered before enrolling in the Colorado State University (CSU) Extension Colorado Master Gardener program and learning how CSU suggests dealing with the following Colorado gardening challenges.

One of the challenges to Colorado gardening is the rainfall or, rather, the lack thereof. Tennessee gets 45-60 inches of annual rainfall while the Pueblo to Colorado Springs corridor averages 12 to 17 inches. This dry climate determines what will grow without irrigation and produces soils with high pH and soluble salt level. In Tennessee, the pH level can be adjusted downward for acid loving crops such as blueberries with ammonium sulfate or elemental sulfur. This seldom works in Colorado because of “free lime”.  As rock weathers into soil one of the end products is lime. Lime leaches out of the soil in regions of high rainfall but remains in arid soils as free lime. Free lime buffers the high pH and brings it back up when it is adjusted downward. To test for free lime, collect an ounce of two of soil and pour a little vinegar over it. If it “fizzes” and gives off gas, the soil contains free lime, making it extremely difficult to adjust the pH. Furthermore, iron is not taken up well by plants in high pH soil. Plants grown in Colorado frequently show iron deficiency as a yellowing of leaf tissue between the veins, known as interveinal chlorosis. Many acid-loving plants such as azaleas and traditional dogwoods simply will not grow in soils with a high pH and are seldom grown in Colorado.

Is there a solution to low rainfall and high pH? Well, partially. First, look at what is native in your area. These plants are adapted to low rainfall (Xeric) and high pH. CSU has developed lists of Xeric and native plants to help you. There are also lists of plants which tolerate high pH, many of which are suitable for our dry climate. These lists can be easily located on the Internet and include CSU Fact Sheets 7.228 – Xeriscaping: Creative Landscaping; 7.229 – Xeriscaping: Trees and Shrubs; and 7.231 – Xeriscaping: Perennial and Annual Flowers. Secondly, consider placing at least part of your garden in raised beds or containers that you can fill with garden soil with a pH of your choice. Lastly, be prepared to water at least while plants are becoming established and perhaps forever if you plant non -xeric plants. Water restrictions may or may not allow watering outdoor plants in your area of Colorado, but that topic is complex and deserves another article.

Soil compaction is another soil-related challenge of many urban Colorado landscapes. The ideal soil has about 25% air, 25% water, 1-5% organic matter and 45-49% mineral solids. However, many native Colorado soils have a high clay content and a low organic matter content causing the soil to compact under pressure of machinery or even foot traffic. Once soil is compacted it remains compacted, holds little air, has poor drainage, and is unsuitable for all but a few plant species.

Compacted soil can be improved by digging it up, breaking up all clods and adding organic matter (compost). Add 1-3 inches of compost for every 6-8 inches of depth that you dig. Plant recommended native plants or those on CSU’s “Front Range Tree Recommendation List”, Fact Sheet 7.415 – Deciduous Shrubs and 7.422 – Native Shrubs for Colorado Landscapes. Pay attention to CSU’s tree planting recommendations (CMG Garden Notes 630 through 636) which are designed to quickly develop a shallow root system so that trees will survive in poorly drained compacted soils. Unfortunately, trees planted using this system will require intense watering at first and some supplemental water throughout their lives. Use organic mulches and additives to gradually improve your soil (CSU Fact Sheet 7.214 – Mulches for Home Grounds). Lastly, plant on berms or slopes. Turning a flat flower bed into a berm or series of low mounds, walking between the mounds and planting on the top and sides of the mounds will decrease future compaction and significantly increase drainage and plant survival.

Colorado weather also poses challenges to gardening. The growing season is short and only a portion of it is hot. Yet the sun is very bright and hot because of the elevation and even plants that are supposed to grow in full sun may require some afternoon shade in Colorado. Snow is possible throughout much of May and again by early September.  Therefore, I recommend not planting plants that require high heat for extended periods of time to mature such as okra, Southern peas and even the larger tomato varieties. Look for quick maturing vegetable or ornamental varieties and consider compensating for the shorter growing season by beginning with large transplants. You can also use season extending techniques such as floating row covers to extend the season and to protect plants from insects and high winds.  Since there may be several weeks between the first and the second fall frosts, season extending techniques can really pay off in Colorado.

Colorado can be extremely windy. The winds along Fountain Creek where we live seem to blow mostly from the north or south and seldom from the east or west. Wind can cause damage to plants so consider using windbreaks. Research shows that a windbreak with a density of 40-60% reduces wind speed better than one which is solid. Staking plants will also help. Microclimates are also important. Sheltered spots can be less windy and significantly warmer than fully exposed sites. South slopes are warmer than north slopes, slopes are warmer than valleys, rocks and pavement retain heat, etc.

Hail is yet another challenge for the Colorado gardener. Hail is much more frequent in Colorado than any other place we have lived and can turn a beautiful garden into an area of total destruction in only a couple of minutes. There are hail cloths sold locally which will protect plants if they are in place when hail begins. We have seen gardeners put a fence around their yard and plant in narrow beds against the fence. Hail cloth can then be attached to the fence and pulled over the beds when severe weather threatens. This cloth has the additional advantages of reducing light intensity and wind speed. You can also make a small cage of PCV pipe, cover it with chicken wire and then with shade or hail cloth. This works well to protect a few prize plants or a small vegetable garden, but the entire cage must be securely fastened down.

Lastly, last year we were visited by numerous tiny grasshoppers early in May. We assumed that they would become less numerous during the season as birds ate them and as they died of natural causes. Instead, they grew rapidly and became increasingly numerous in our garden as the summer progressed. They were attracted to our growing plants from the dry surrounding area, and we ended up with far more than our share of grasshoppers. By the time we attempted to control them chemically they were too large to be easily killed. They ate about everything and decreased in numbers only with fall frosts. This year when we see numerous little grasshoppers we will begin controls while they are small. Perhaps the grasshopper baits found on the Internet and at some local garden centers will attract and kill them without using widespread chemicals.

All of this sounds like having an attractively landscaped yard in Colorado is a lost cause, but we remain optimistic that attractive landscaping is possible even if not as easy here as it is in other locations we have lived. The following tips may help:

• Both Colorado Springs and Pueblo have demonstration xeric gardens. Look them up, visit them, and take notes.
• CSU publishes a variety of materials concerning what will grow here and how to garden in our conditions. These materials include “Garden Notes”, “PlantTalk”, numerous “Fact Sheets”, plant lists, etc. Take advantage of what others have learned by becoming familiar with this material.
• Concentrate on plant groups or species that are adapted to Colorado conditions such as cacti, succulents, and native plants. There are several hundred sedum species, many of which will do well in Colorado. penstemons, gaillardia, iris, Agastache, flax, lilac, and sunflowers all perform well here. Many ornamental grasses are also quite attractive year-round and grow well in Colorado.
• Pay attention to cultural techniques such as planting in containers, raised beds or on berms where you create paths to walk on and avoid compacting soil. Also use mulch to retain precious moisture and water plants until they are established.
• Forget about all those beautiful things you used to grow and concentrate on what you can now grow. Your Colorado garden will slowly improve both because you get better at growing what will grow and because you learn to stretch the boundaries of what will grow. As your garden improves so will your satisfaction with Colorado gardening.

Source: The CSU Extension website “https://extension.colostate.edu“ .