Challenges to gardening in Colorado
Spring moisture brings brown ground to life. Plant species of all kinds slowly grow and green up, and those with a green thumb anticipate their first days in the garden.
Gardening in Colorado can be a fun, rewarding experience if done properly. However, the climate can be challenging, and amateur gardeners may find themselves struggling.
“In moderate climates, gardening is a fairly predictable endeavor. In Colorado, my advice is to adopt an adventurous attitude. The accomplishment of growing a gorgeous plant here means more than growing the same thing in areas of the country where anyone can do it,” said Carl Wilson, Colorado State University Cooperative Extension Agent, Horticulture, Denver County.
Those who did not grow up gardening in Colorado may find themselves frustrated. “Newcomers to Colorado often have trouble getting plants to survive, let alone thrive. More often than not, they previously gardened where ‘you stick a plant in the ground and it grows.’ Typically, those from northern states such as Minnesota or Michigan are puzzled why certain trees that did well for them there do poorly in Colorado,” said Colorado State University Extension landscape horticulturist and professor Jim Klett, and horticulture agent, Arapahoe County Extension Robert Cox, in their fact sheet titled Colorado Gardening: Challenge to Newcomers, published in March of 2013.
They continued, “Winter cold is not the only factor that determines plant survival. Low humidity, drying winds and physical properties of the soil also influence how well plants perform here.”
Elevation is the first challenge that gardeners face. “The average elevation of the state is 6,800-feet above sea-level. Three-fourths of the nation’s land above 10,000-feet is within its borders. Due to the high elevation, sunlight is frequently of high intensity and the humidity generally is low. These features, along with rapid and extreme weather changes and frequently poor soil conditions, make for challenges in growing plants,” they stated.
The next challenge is due to the soil. “Many of our population centers are on heavy clay soil. These soils have poor aeration that limits root growth. Thus the ability of plants to replenish water loss brought about by low humidity and wind is limited. Adding more water to such soils further complicates the problem because the water added reduces the amount of air in the soil, causing oxygen starvation to the roots. Little can be done to modify humidity and wind, so the obvious solution is to improve the soil,” Klett and Cox said.
They continued, “High soil pH can also negatively affect plant growth. Basically, pH can be described as the measure of acidity or alkalinity of soil. Iton is measured on a scale of one to 14 where seven, which is neutral, is the optimal level for most plants. Numbers lower than seven are considered acidic and numbers higher than seven are considered alkaline or calcareous (high in calcium carbonate). Colorado soils that have never had amendments added may have a pH value of up to 8.5, which is higher than most plants can tolerate — especially acid-loving plants such as rhododendrons.”
Salt accumulation can also be an issue. “Soil modification or amendment is a problem in our semiarid, highly alkaline soils. Organic matter, if added in large amounts all at once, can provide for a more porous soil. However, this practice can lead to the accumulation of soluble salts. Unless the soil is porous so that salts can be leached away with water, the salts tend to accumulate in the amended soil layer. The soluble salts may remain in the organic matter much like water remains in a sponge. Rapid evaporation may concentrate the salts in the root zone, where they can injure plant roots,” they said.
They added, “A solution to this problem is to slowly, over a period of years, improve the soil tilth. Tilth refers to the physical properties of soil which make it able to support plant growth. An alternative to leaching salts and improving soil tilth is to choose plants that are more tolerant of saline soil conditions. For instance, instead of planting a pine knowing that it would do poorly under saline conditions, one may have to settle for a juniper. Look to Colorado native plants native to your life zone and soil conditions for more options.”
In addition to having clay soils, the ground can also have a high level of iron. “The name Colorado comes from the Spanish words ‘color rojo,’ meaning color red, referring to the dominant red soils. The red color is due to high amounts of iron in the soil. Yet, a yellowing condition in certain plants, known as iron chlorosis, is brought about by an iron deficiency in the plant. Colorado’s highly calcareous soils tie up the iron in a form unavailable to the plant,” they stated in the fact sheet.
They continued, “Making iron more available is not easy and usually not economical. Adding available forms of iron such as iron sulfate to the soil is, at best, a temporary measure. Normal chemical reactions in the soil will quickly cause much of the added iron to become unavailable. The best alternative is to select plants tolerant of Colorado’s alkaline soil. Instead of pin oak, choose bur oak or Norway maple instead of silver maple, etc.”
Weather is also a factor, with late snows and frosts, and rapid changes in temperature, especially in the spring. “Occasionally, Colorado will experience frosts when plants aren’t ready to cope with them. It is not uncommon for mountain communities to have an already short growing season interrupted by a killing frost. Gardens in areas where cold air is trapped may have earlier frost kill than gardens even a short distance away. Cold air may be trapped by any obstruction on the down-slope side of a garden, such as a hedge, wall or solid fence. To avoid early cold injury to gardens, do not put hedges, fences and other landscape features where they may obstruct the flow of air,” Klett and Cox stated.
Even with these challenges, there are several advantages to gardening in Colorado. “Colorado’s many days of sunshine, while leading to some problems already mentioned, enables gardeners to grow some of the best flowers in the nation. The high light intensity produces strong-stemmed plants and flowers with extra brilliance,” they said.
The continued, “Winter sunlight melts snows at lower elevations, reducing snow mold diseases in lawns. The cool, crisp nights and warm days of summer produce healthy lawns. These same climatic conditions enable the home gardener to produce excellent potatoes, cabbage, lettuce, broccoli, cauliflower and other cool-season vegetables. The lower humidity not only helps to make the cold days seem less cold and hot days less hot, but discourages many plant diseases that are common in more humid areas.”
Many gardeners enjoy the challenge of growing in the state, however. “Perhaps the brightest side lies in the challenges of problems growing plants in Colorado. Gardeners who are patient, know how to select plants that will do well, and manipulate the soil and microclimate will be amply rewarded,” Klett and Cox stated.
Experience is the best teacher, and after time, gardeners in Colorado can find success. “The best advice for a vegetable gardener new to the area is to be flexible, be adaptable to weather changes, try a variety of gardening methods and know why they are working for you, and to enjoy the challenge of it all,” said Wilson.
For questions about gardening in Colorado, contact your local Master Gardener. A list can be found at http://CMG.ColoState.edu/Ask-CMG.shtml. ❖