What zone is colorado?

New plant hardiness zone map means changes for mountain gardeners

If you grow any plants in Colorado, your zone is everything!

The USDA has just released the 2012 Plant Hardiness Zone Map that could put you in a whole new zone.

What is a hardiness zone?

The USDA’s zones are based on the average low winter temperature for an area. In Colorado, our zones range from the cold Zone 3a (-40 to -35 degrees F. ave. low winter temp) to our warmest Zone 7a (0 to 5 degrees F. ave. low winter temp). Across the United States, many areas have gone up to be one-half zone warmer. But USDA cautions this is often less about global warming than it is about more accurate monitoring of temperature data. And in mountain areas, because we now have better data, many areas have been re-classified to a colder zone.

What does this mean for Colorado gardeners? Even if your area has moved up from 5b to warmer 6a, you need to know that any given year, the low temp could still bottom out below the average noted in the zone. So if you start planting 6a plants, put them in protected areas and know that in extremely cold years, there could be winter die back.

We need to pay attention to our zones because they relate to winter hardiness – one of the most critical factors for ongoing plant survival. Still, bear in mind that zone shifts don’t mean that scorching heat, high winds, poor soils, lack of water or an occasional extremely cold winter will go away. All of Colorado’s challenging growing conditions make up our bottom line.

Success in the garden means checking seed packets and nursery catalogs to make sure plants you buy grow in your zone. And, planting in the right exposure, using soil amendments and grouping plants based on similar water requirements are still the name of the game.

Courtesy Associated Landscape Contractors of Colorado and Neils Lunceford, a landscaping company based in Silverthorne that is a member. You may contact them at (970) 468-0340.

Colorado Planting Zones – USDA Map Of Colorado Growing Zones

Click on the image above to see a larger version.

USDA Colorado Hardiness Zone Map For Trees And Plants

Above is the map of the USDA Colorado hardiness zones. The USDA created plant hardiness zones to act as a guide for gardeners and farmers. By understanding your planting zone for Colorado, you will be more successful in your efforts to create a wonderful garden.

To find your Colorado hardiness zone, locate the place on the map where you live. The color of that area can be matched to the legend at the right. The legend will tell you your planting zone for Colorado.

This growing zone map is based on the 2012 USDA Colorado plant hardiness zones map. The USDA plant hardiness zone map was revised at that time to show the new climates that have resulted over the past few decades due to global warming.

Understanding your planting zone in Colorado will increase your ability to create a garden that can flourish from year to year. Planting vegetables, trees, flowers and other plants that are appropriate for your zone will make your gardening less frustrating.

Plant nurseries in your area will carry plants that are appropriate for your planting zone. The plants should be clearly marked with the zone it grows in. You can grow plants that are in your zone or lower.

Colorado has a unique climate that can vary from freezing winters to drought-like summers which can make maintaining a beautiful garden difficult without a well thought out plan. Flowers by Season in Colorado Springs is geared towards Colorado Springs’ climate, but we also recommend keeping your local climate in mind when selecting plants.

This guide will help you plant the right types of flowers at the right times which does everything from significantly increasing the curb-appeal of your home to attracting pollinators that fertilize your flowers for you. We’ve also included some ideas to keep your garden colorful in the freezing months without floral blooms.

Want a list of our favorite Colorado flowers plus care instructions? Download this free guide:

Spring: March-May

During the spring months, focus on cold-hearty flowers which stand a better chance of surviving any late freezes. Think Easter colors with beautiful pinks, purples, and whites. Bulbs planted last year should pop back up this time of year as well.

Spring Colorado Flower Favorites:

  • Tulips (bulb-planted in Fall to bloom in Spring)
  • Iris (bulb-planted in Fall to bloom in Spring)
  • Daffodil (bulb-planted in Fall to bloom in Spring)
  • Hyacinth (bulb)
  • Pansies
  • Snapdragon
  • Decorative Kale
  • Alyssum

Summer: June-August

Summers in Colorado Springs provide the opportunity to plant and enjoy a wide variety of beautiful flowers. Keep in mind we don’t receive enough humidity or rainfall to sustain tropical plants. Drought-tolerant flowers and Colorado native plants will handle hot summer days the best. These native plants are naturally adapted to their specific Colorado Climate, soils, and environmental conditions. Also, including mulch beds can be especially useful in the summer months to maintain a cool soil temperature.

Summer Colorado Flower Favorites:

  • Petunia- come in a wide variety of colors.
  • Coleus
  • Zinnias
  • Marigold
  • Potato Vine
  • Geranium
  • Annual Salvia

Fall: Sept-November

Fall is the perfect time to start planting spring bulbs before the soil freezes. Planting your bulbs mid-fall can give them an opportunity to grow a well-established root system. It is also time to think about cold-hearty flowers which can survive falling temperatures. The fall flower color palette includes reds, oranges, and yellows. Consider adding pumpkins, squash, and other gourds for a fun fall arrangement. Keep in mind, this is the last chance to plant perennials before the first freeze.

Now is the time to think about what fall bulbs you would like to plant to pop up next spring!

Fall Colorado Flower Favorites:

  • Mums- in white, orange, purple
  • Ornamental Kale
  • Pansies
  • Millett Grasses
  • Decorative Peppers
  • Plant any bulbs you want to come up in spring

Winter: December-February

While flowers cannot survive the freezing winter temperatures, it is still possible to add some pizzazz to your flowerpots and beds for the season. This is an ideal time to lay mulch over your fall planted bulbs as well.

  • Purchase evergreen tree tops from your local Christmas Tree Farm. These are just 1 to 2 feet tall and you can place them in pots or beds as tiny Christmas trees.
  • Drape evergreen plants with decorative ribbon.
  • Add pinecones to pots to add interest.
  • Christmas Décor and lighting

Winter is also the perfect time to grow an indoor herb garden, especially if the cold season and lack of plant life gets you down. Some of our favorites are basil, chives, mint, parsley, and oregano. Use a sun lamp or place in a room with natural light to keep these plants happy and healthy. Bonus: There is nothing better than cooking with your own freshly grown herbs.

ANNUALS, PERENNIALS, AND BULBS: Flowers by Season in Colorado Springs

Having a mix of annuals, perennials, and bulbs helps maintain a beautiful garden from early spring to late fall. Annuals typically require the most consistency in fertilizer to grow beautifully because the plants’ life cycle is only one growing season. Keep in mind that your perennials may not live forever, but proper care can keep them thriving year after year. Since perennials have more established root systems, they require less water and less fertilizer, but consistency is still key when caring for these flowers. Plant bulbs that you would like to come up in Spring during Fall before the soil freezes. Bulbs especially love a layer of mulch placed over them in winter to help the soil temperature stay consistent. Keep these differences in mind when planning your flowers by season.

General tips to keep your flowers looking awesome year-round:

  • Keep spacing in mind when planning your garden – Planting flowers too close together makes them compete and planting flowers too far apart can make your garden look patchy.
  • Remove “dead heads” (also known as withered flower heads) – Removing dead blooms allows the flower’s energy to be put towards the growth of beautiful new blooms and keeps your garden looking fresh.
  • Follow a regular watering schedule and adjust according to rain levels.
  • Fertilize with Bloom Booster monthly to encourage growth.
  • Amend the soil with compost prior to planting and add a layer of mulch over the top.
  • Be proactive by checking your garden throughout the season for rot, diseases, and bugs.

A colorful; flower bed can make a statement and really provide a wow factor in your landscape. For more flower-planting guidance, contact the experts at Timberline Landscaping via the form below.


The Centennial State enjoys sunny weather virtually all year round. While it does have its cold winters, they are significantly better with sun, and summers are usually marked with low humidity. When combined with the state’s high elevation, they make for cooler summer days.

Choose Colorado declared that the state’s climate is its best kept secret.

Climate Zones in Colorado

U.S. climate zones.

But of course, different parts of Colorado still have differing climates given its vast size. It’s the 8th largest state by land area. The variations result primarily from dissimilarities in terms of terrain and elevation. In fact, the state features 4 out of the 8 climate zones in the country.

Rocky Mountains

Winter in RMNP. Photo: katiebordner

Colorado is best known for its mountains. Albeit they only cover a minority of the land area, their presence has a significant impact on the climate of the state. They can shelter lower areas from adverse weather patterns, as well as air movements.

The mountainous areas generally have lower temperatures, thanks to their altitude. Interestingly, the valleys are often cooler compared to the peaks at night because the mass of cool air settles along the former.

During summer, daytime sees comfortably warm weather, while nights remain cool. You may even skip turning the A/C on at night, which could contribute to better sleep. Fresh air helps in getting a good night’s rest> due to the body being more relaxed in a natural environment. Just bear in mind that the mountains are the first to be affected by the weather so it’s recommended to check the forecast regularly.

Eastern Colorado

Thunderstorms in northeastern Colorado by Akron. Photo: Bo Insogna

The Colorado Encyclopedia specified that Eastern Colorado has a uniform climate practically all year round, with plenty of sunshine and limited snow. Despite its semiarid condition, the air remains relatively cool thanks to the low precipitation in the air.

Temperatures in summer reach an average peak of 95 degrees F, while the coldest winters register temperatures as low as minus 15 degrees F. Spring usually sees heavy and frequent rainfalls, although storms are more likely to occur during fall and winter months. Strong winds are also plentiful during winter and spring, which during times of drought can cause dust storms.

Grasses, particularly buffalo and grama grass, are abundant in the Eastern Plains of Colorado. Many cattle farmers have set up base in this area to allow their cows to graze.

Western Slope

Mt Garfield in Grand Junction. Photo: Rob Lee

The Western slope pertains to the parts of Western Colorado not covered by the mountains. Many of the lands in this area are mesas and plateaus, and generally at elevations below 7,000 feet, according to the Denver Channel.

The weather patterns in this area are dependent on the orientation of the mountain ranges, the amount of sun, and the amount of air circulating in the different regions. As such, a higher elevation does not automatically translate to cooler weather, but not as cold as the mountains, although winters may become harsher the higher the area. In fact, it’s possible for different towns in the western slope to have different climates, despite the short distances between them.

Areas near Grand Junction commonly experience weather similar to the Eastern Plains. The climate is mild enough that it allows farmers to cultivate fruit trees. It’s also this part of the state that s considered as Colorado’s wine country. Parts of southwestern Colorado have weather similar to the plains as well, with abundant sunshine and light winters, exceptions being high mountain towns of Telluride, Silverton and Ouray.

Flash floods may also occur on the Western slope. However, residents don’t experience these as frequently as those living in the other parts of the state due to its lower precipitation levels. This region is also less prone to tornadoes compared to the Eastern Plains

Ecological Zones

The ecological zones of Colorado are also worth noting. The state is broadly divided into four regions: steppe, foothills, coniferous forest, and alpine tundra zones, as identified by Britannica.

The steppes, which can be found on the plains of Colorado, are covered by short grasses, which are exploited by farmers for cattle grazing. The foothills zone, which has an elevation of 5,500 to 7,000 feet, has juniper, mountain mahogany, piñon pine, and oak as its endemic plants. The coniferous forest, meanwhile, is predominantly populated by evergreen trees: Douglas fir, ponderosa pine, and spruce. Finally, the alpine tundra zone has limited vegetation, most of which are mosses, lichens, and sedges.

USDA Plant Hardiness Map.The United States Department of Agriculture (USDA) established plant hardiness zones to serve as a guide for farmers and gardeners to determine what to grow and when to grow them. By understanding your zone’s climate, you stand a greater chance of succeeding in planting and harvesting produce, trees, flowers, and other plants. The plant hardiness zone map divides the state of Colorado based on their respective zones, with 3a being the coldest, to 7a, which is the warmest.

Travel tips

  • Winter remains the best time to visit Colorado if your intent is to go skiing. It’s best to head out to the slopes during the morning when it’s covered with fresh snow, or at least freshly groomed corduroy. Travel + Leisure suggests bundling up when heading to the mountains, because storms happen.
  • If you’ll be traveling during summer, make sure to bring a light jacket along with your shirts and shorts. Like stated earlier, this is because nights can still remain cool even during this season and cool weather can strike at anytime.
  • Given that the climate of Colorado changes depending on what part of the state you’re in, USA Today advises packing travel items for all seasons. It’s advisable to bring sunscreen and lip balm even during winter to help keep your skin safe from the sun.
  • Winter evening in the Rockies.

  • Be sure to always bring a drinking flask to keep yourself hydrated. It’s necessary not just for warm weather, but when it’s cold as well. High altitude and cold weather, combined with a dry climate, can cause a biological process known as cold diuresis. This is why people tend to urinate more often when it’s cold. It’s important to always be ready to replace lost fluids.
  • Because Colorado weather can be very unpredictable, it’s a good idea to dress in layers before heading out so it would be easy for you to adjust accordingly.

Colorado is a landscape of varying climates, where you can ski in the morning and enjoy a warm afternoon in the park, just by heading down in elevation. Expect the worse weather and you’ll probably get the best. Enjoy this wonderful state!

Colorado Hardiness Zones and When to Plant in Colorado

What should you be doing in the yard and garden this month? It’s a perpetual question of Colorado gardeners. How do you write a reliable to-do list for Colorado gardens when we can see three seasons in a single weekend — or in a single half-day drive? It might be spring in Fort Collins, still winter in Aspen, and already summer in Pueblo. Even the rule of thumb “Never put your plants out for good until after Mother’s Day,” can stand to be played by ear from year to year.
It’s usually best to take seasonal lists as a guide, not a rule, and remember that we can swing from snow-covered to too hot and too dry in a couple of weeks. (And then swing right back.) Generally, care for cool-season lawns and treat for weeds in spring and fall; trim fruit trees anytime before the weather warms; plant water-wise selections at all times; and care for your soil, which in Colorado, isn’t the world’s richest as a matter of geography, year-round.

Here’s two handy infographics:

Confused about your USDA Hardiness Zone for planting purposes? Here’s a handy map:

Once you’ve determined your general zone, you can use this guideline to determine relative safe planting dates:

for most of us along the Front Range, Mother’s Day is a pretty safe bet – but just in case, don’t forget to mulch young and tender shrubs and trees. Also tree and bush spraying will control insects and pestsSee tips on effective mulching at Colorado Master Gardener’s GardenNotes.

Happy Planting and Happy Spring!

Question: I am receiving a lot of nursery catalogues and all of them end the plant description by giving a zone designation. What does this mean?

There are 10 planting zones in the United States and each zone indicates a 10 degree Fahrenheit difference in the average minimum yearly temperature. A quick look at the hardiness zone map shows elevation and distance from the equator affect the temperatures in the U.S.

Warmer areas have higher numbers. Southern Florida is in Zone 10, where tropical plants can be grown outdoors, year-round.

Colder areas have lower numbers. Northern parts of Montana, North Dakota and Minnesota are in the coldest zone in the U.S., Zone 3.

To add a little more precision to the zone designations, each zone is divided into 5 degree increments, “a” or “b.” Colorado Springs is in Zone 5b. Black Forest is in Zone 5a. Teller County, like most of our mountain areas, is in Zone 4.

But there are other important factors that affect our growing season. Some 40 years ago Sunset magazine developed zone maps which cover Colorado and 12 other Western states. The Sunset map zones use a more precise 24-zone climate system that shows maximum and minimum temperatures, length of the growing season, humidity and rainfall patterns. Colorado Springs is in Sunset’s Zone 1, which is considered to be an area with the coldest winters. Their Web site is www.sunset.com/garden/climate-zones.

The concept of a plant hardiness map was started at the Arnold Arboretum at Harvard University. The USDA and Harvard University developed the hardiness zones during the 1920s and ’30s, and the hardiness zone maps were first published by the U.S. Department of Agriculture in 1960.

The map is modified every 15 years, reflecting gradual climate changes. The last map was revised by the National Arbor Day Foundation in 2006.

Most gardening reference books, nursery catalogues, gardening magazines and Extension Service publications refer to the USDA hardiness zones. However, gardeners must recognize that the map is only a guideline; it does not consider many factors necessary for plant survival.Additional factors

Knowing the cold hardiness of any given plant is important, but a gardener needs to consider other factors which influence plant survival. Soil types, moisture, altitude, daytime temperatures, day length, humidity, planting location, snow cover, wind and heat are some of the factors one needs to consider. In this area gardeners often need to consider deer- and rabbit-resistant plants.Some gardening practices may make plants more susceptible to freezing problems.

If a gardener applies nitrogen fertilizer to plants after July, the plants may grow too rapidly and not adjust to freezes properly, increasing the susceptibility to frost damage.

Container plants are more susceptible to having frozen roots. The ground, being dense, resists freezing, so plants survive winters much better when their roots are in the ground.

Most evergreens are well suited to Colorado, but they continuously lose moisture from their needles during the winter. Cold temperatures won’t kill them, but winters without adequate snowfall will. It is important to provide trees and bushes with supplemental water during the winter, about five to 10 gallons per inch of trunk diameter each month.

-For gardening information and additional links, visit the Colorado Master Gardener Web site at cmg.colostate.edu.

Colorado State University

Print this fact sheet

by J.E. Klett and R. Cox* (3/13)

Quick Facts…

  • Low humidity, fluctuating temperatures, alkaline clay soils and drying winds often restrict plant growth more than low temperatures.
  • Selecting plants that tolerate our soil and climatic conditions is key to Colorado gardening.
  • Colorado grows excellent flowers, vegetables and lawns.
  • Gardeners who are patient, know how to select plants that will do well, and manipulate the soil and microclimate will be amply rewarded.

Gardening in Colorado can be challenging. 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.

Newcomer’s Dilemma

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.

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.

Soil Properties

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. See fact sheet 7.235, Choosing a Soil Amendment.

High soil pH can also negatively affect plant growth. Basically, pH can be described as the measure of acidity or alkalinity of soil. pH is measured on a scale of 1 to 14 where 7, which is neutral, is the optimal level for most plants. Numbers lower than 7 are considered acidic and numbers higher than 7 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.

Why Not Rhododendrons?

Newcomers, particularly those from coastal states such as California, Oregon, New York and the Carolinas, frequently express surprise and disappointment in the lack of broad-leafed evergreen plants such as mountain laurel, rhododendron, pittosporum and similar plants. Our highly calcareous soils and rapid changes in our winter temperatures are partly responsible for this. However, the primary limiting factors are low humidity, drying winds and intense winter sunlight.

Mountain laurel, rhododendrons and similar types of plants can grow in Colorado if the soils are carefully amended to make them more acidic and where the plants are protected from winter wind and sun. Even broadleaved evergreens that can tolerate alkaline soils and lower humidity, such as wintercreeper, English ivy, kinnikinnick and Oregon grape-holly, will perform best in a shaded north or east exposure.

Salt Accumulation

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.

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.

Iron Problems

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.

Trees with high iron requirements such as pin oak, silver maple and red maple perform poorly in Colorado’s alkaline, calcareous soils.

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.

Untimely Snows

In Colorado, heavy, wet snows in the late spring or early autumn are common. Trees, shrubs and perennials are caught in full leaf or just at the peak of bloom. These “limb-breaker” storms cause severe damage that leaves permanent scars and tends to keep trees to smaller-than-normal size.

Following such a storm, tree diseases tend to increase. Broken limbs and central leaders can cause problems for trees for many years. To minimize damage, choose less brittle trees such as lindens, oaks and conifers instead of silver maple, Siberian elm and willow. This, however, brings about another dilemma. The less brittle ones are also the slower-growing ones.

What About Freezes?

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.

In Leadville with an elevation of 10,177 feet and an average growing season of about 25 days (compared with over 150 in many areas on the plains), a frost may occur in July. Yet, with careful selection of plants, even Leadville can flaunt colorful garden flowers, vegetables and hardy trees and shrubs.

Table 1 lists average frost-free periods for selected cities at several elevations in Colorado. While growing seasons tend to be shorter at higher elevations, use caution when interpreting this table. Note that some higher elevations have a longer season than lower elevations. Compare, for instance, the average growing seasons of Dillon, elevation 9,800 feet with that of Fraser, elevation 8,560 feet. Fraser is lower than Dillon, but has a shorter average growing season. A primary reason is air drainage; Fraser has shorter seasons because of cold air drainage from surrounding mountains.

The same air drainage phenomenon can make a difference in the location of a garden. 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.

The real killers, however, are the infrequent but rapid changes from warm, balmy weather to cold, subzero temperatures. In 1949, a 90 degree F change was recorded near Fort Collins in less than 24 hours. The change from 50 degrees F to -40 degrees F resulted in the ear-popping fracture of entire trees and virtually wiped out the local sour cherry industry. On October 19, 1969, Denver experienced a temperature drop to -3 degrees F, that was preceded by balmy 85 degree weather. Similar rapid temperature changes occurred on September 17, 1971, and October 28, 1991.

Such freeze injury leaves crippling marks on trees and shrubs for years and serves to eliminate many plants with borderline hardiness. Most severely injured in such freezes are the lush, rapid-growing trees, because they have a higher internal moisture content than the slower-growing, more solid wood species. To help reduce injuries from such sudden temperature changes, gradually reduce water in late summer and avoid late applications of fertilizers high in nitrogen.

Table 1: Elevation and average growing season
for selected Colorado cities.
Location Elevation Average Frost-Free Days
Alamosa 7,536 95
Aspen 7,913 88
Bailey 7,733 82
Boulder 5,444 156
Burlington 4,167 153
Center 7,668 96
Colorado Springs 6,090 152
Craig 6,247 98
Crested Butte 8,855 37
Denver 5,280 155
Dillon 9,800 25
Durango 6,554 110
Eagle 6,497 86
Fort Collins 5,004 142
Fraser 8,560 9
Grand Juction 4,597 183
Gunnison 7,694 62
Idaho Springs 7,569 93
Leadville 10,177 26
Meeker 6,242 91
Mesa Verde 7,070 148
Monte Vista 7,665 97
Monument 7,400 150
Norwood 7,017 108
Pueblo 4,639 158
Salida 7,060 109
Steamboat Springs 6,770 46
Trinidad 6,030 152
Walsenburg 6,221 148
From: The Western Regional Climate Center www.wrcc.dri.edu/summary/climsmco.html
accessed 11-17-2006.

The Brighter Side

For more information on native plants see fact sheets
• 7.421, Native Trees for Colorado Landscapes
• 7.422, Native Shrubs for Colorado Landscapes
•7.423, Trees and Shrubs for Mountain Areas

Up to this point, gardeners might want to throw up their hands and say, “What’s the use?” But there is a brighter side. 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.

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. 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.

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Colorado State University Extension landscape horticulturist and professor, department of horticulture and landscape architecture; R. Cox, horticulture agent, Arapahoe County Extension. Revised from original fact sheet authored by J.R. Feucht, retired. 12/96. Revised 3/13.

Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.

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Ari LeVaux is a contributor to Writers on the Range, the opinion service of High Country News. He writes about food in Montana.

This is the time of year to think about planting trees. It’s a powerful, important and often a genuinely fruitful thing to do. Planting a tree is also a long-term commitment. It requires a deep look into the future, and given the way the climate is shifting around us, it’s like aiming at a moving target you can’t even see.

The U.S. Department of Agriculture’s plant-hardiness zone boundaries are marching steadily northward, as can be seen on a map loop. In the 15 years since my friend Tom McCamant planted his peach orchard in northwest Montana, his land has been reclassified from Zone 5b to 6a.

It wasn’t long ago that if you wanted to grow peppers here in Montana, you had to plant them in a greenhouse. Now we get outdoor peppers every year. Ranchers who used to get two cuttings of alfalfa are now getting three. Pasta makers are already looking northward, in search of the next hotspot for the best durum wheat. Some wine grape growers are preparing to move north as well.

The plant hardiness zones are based on overnight lows, which determine both the growing season for annuals and which trees can hang through the depths of winter. These constraints can be increasingly finagled with the help of a growing arsenal of clever tricks that farmers are coming up with to control the climate around their crops.

Early apricot tree blossoms. Emily Neef/Flickr user

Such measures can help extend the season for greens deep into winter, or set up an early start for next year, or allow risk-tolerant growers to take a chance on some exotic thing that shouldn’t have any business growing here. At the farmers market in Missoula, Montana, you can now get fresh ginger along with okra, artichokes and freshly roasted green chile (not necessarily a serving suggestion).

“Most of the country has moved up a zone from where they were in 1980,” McCamant says. “The best opportunities in agriculture right now are in marginal spaces.”

McCamant would know. When he was planting his Forbidden Fruit orchard, extension agents and agriculture academics told him that peaches were at best a marginal crop in Montana. Now, his many varieties, some of which are grapefruit-sized, have become a prized delicacy in the region. The lengthening summers and shrinking winters have generally been good to his orchard, in terms of quantity as well as quality. Bumper crops have become the new normal at Forbidden Fruit.

“But it’s a double-edged sword when you bloom early, because you still get those cold snaps. You increase the chance of frost damage,” McCamant says. “Weather in spring and fall is a lot more unstable these days.”

McCamant has a frost protection system that consists of a series of fans called “cold air drains,” and the occasional sprinkler to form a brief line of defense against frost. Last year, he spent more time running frost protection than sleeping. He operated it for 14 nights between April 1, when the peaches bloomed, and April 20, when they used to.

But a March bloom would be tougher to manage for his system, which can only buy a few degrees. And a February bloom would mean he could take the summer off, unpaid.

“Februarys have been warming faster than just about any other month,” McCamant noted. “Having an early bloom once in awhile is to be expected,” McCamant says. “But having two early blooms in a row, that’s a first.”

While there’s no doubt that warmer days are coming, it’s less clear what to do about it. My yard is home to a Chicago fig that is rated for zone 5, my current hardiness zone, and a Russian pomegranate that supposedly needs a zone 6, the edge of which is a few miles to the west and approaching. At the rate we’re going, we might already be there.

Messing around with hobby plantings like this isn’t a substitute for getting out there and doing something about saving the planet. But if there was any lingering doubt that things are changing, watching the trees might set that aside. Though some new plants will grow, we can also expect others to die. Sugar maples, for example, are more vulnerable to disease during warm winters, which give many pests the upper hand as well. Pollination patterns are also changing.

With all of that in mind, it’s time to order trees. No more pomegranates and figs for me — at least until the first ones prove themselves. Some peach trees are in order, and McCamant recommends a variety called “Reliance.” I’m going to order a plum tree, too, albeit with some trepidation: It’s a cold-weather tree.

Note: the opinions expressed in this column are those of the writer and do not necessarily reflect those of High Country News, its board or staff. If you’d like to share an opinion piece of your own, please write Betsy Marston at .

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