Discover Colorado’s Planting Zones — Plus 7 Keys to Keep Flowers, Shrubs, and Trees Alive

Landscape photo of Maroon bell at Colorado. in Aspen Colorado autumn season.
© thanasarn/Shutterstock.com

Written by Kimberly Magerl

Published: September 25, 2023

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In the heart of Colorado’s breathtaking landscapes, cultivating a vibrant garden or nurturing the health of shrubs and trees can be a rewarding yet challenging endeavor. Understanding Colorado’s planting zones is paramount to ensure your greenery thrives in this state’s diverse climate. Discover the significance of these zones, decipher the hardiness zone map, and unveil seven keys to keeping your flowers, shrubs, and trees alive amidst the Rockies’ unique conditions.

Understanding Planting Zones

Colorado’s diverse geography and varying elevations create a wide range of microclimates, making it essential for gardeners and landscapers to understand planting zones. These zones, often referred to as USDA hardiness zones, are geographical regions categorized based on the average annual minimum temperature. Additionally, the primary purpose of these zones is to help gardeners select plants, shrubs, and trees that can withstand their local climate’s temperature extremes.

The hardiness zone map serves as a valuable tool for gardeners and landscapers in Colorado. By identifying your local zone, you can make informed decisions about which plants, shrubs, and trees are most likely to flourish in your specific area. This knowledge helps you avoid planting species that might struggle to survive in the Centennial State’s unpredictable weather patterns, including frosty nights and rapid temperature fluctuations. Understanding your planting zone is the first step in creating a resilient and thriving garden or landscape in Colorado.

Colorado’s Planting Zones

In Colorado, you’ll find a range of zones, typically spanning from Zone 3a in the coldest mountain areas to Zone 7a in the warmest regions along the Front Range. The state’s diverse landscape, spanning from the plains to the Rocky Mountains, is home to a variety of temperature extremes.

A map showing Colorado's planting zones

Colorado’s USDA Plant Hardiness Zones range from 3a to 7b.

©https://planthardiness.ars.usda.gov/ – Original / License

The High Country Zones (Zones 3a-4a)

In the high mountain regions of Colorado, you’ll find Zones 3a to 4a. These zones are characterized by extremely cold winters, with temperatures dropping well below freezing. If you’re gardening in the high country, it’s essential to choose cold-hardy plants that can withstand harsh winters. Consider native alpine species and cold-tolerant shrubs and trees for your garden.

The Foothills and Western Slope (Zones 5a-6b)

Moving down from the high mountains, you’ll encounter Zones 5a to 6b in the foothills and western slope areas. Here, the climate is milder. However, the regions still experience cold winters and occasional frosts. Many fruit trees, ornamental shrubs, and perennial flowers thrive in these zones. However, gardeners should remain vigilant for late spring frosts that can damage tender new growth.

Front Range and Plains (Zone 7a)

Along the Front Range and in the eastern plains, you’ll find the relatively warm Zone 7. This zone offers a longer growing season and milder winters compared to other parts of the Centennial State. Gardeners here have a broader range of plant options, including various vegetables, annuals, and perennials. However, the region’s semi-arid climate requires careful water management.

Plants for Colorado’s USDA Hardiness Zones

Choosing the right plants for your specific USDA hardiness zone is essential to ensure your landscape thrives in Colorado’s climate.

Plants for Zones 3a to 4b (High Country)

In the high country zones, where frigid winters are the norm, hardy and resilient plants are a must. Opt for native alpine flowers and shrubs that have naturally adapted to the challenging high-altitude conditions. These plants thrive in the tough local environment. Additionally, prioritize plants with high cold tolerance. Look for species that can withstand freezing temperatures, heavy snowfall, and sudden temperature fluctuations, which are common in these areas.

While cold is a significant factor, high-altitude regions in Colorado also experience dry conditions, so plants that conserve moisture are valuable. Consider drought-resistant landscape plants to ensure longevity. Lastly, ensure that your chosen plants are suitable for the specific soil types found in high country zones. Amending soil may be necessary to provide optimal growing conditions.

Popular plants for the High Country include: 

  • Alpine currant (Ribes alpinum)
  • Bearberry (Arctostaphylos uva-ursi)
  • Colorado blue spruce (Picea pungens)
  • Colorado columbine (Aquilegia coerulea)
  • Rocky Mountain bluebell (Mertensia ciliata)
  • Western Wood Lily (Lilium philadelphicum)
Mertensia ciliata Mountain bluebells Tall fringed bluebells, purple and blue bells at 11000 ft in the Rocky Mountains, Colorado

Rocky Mountain bluebells thrive at higher elevations and reach up to 3 feet tall.

©cciexplore/Shutterstock.com

Plants for Zones 5a to 6b (Foothills and Western Slope)

Moving to the foothills and western slope regions, you have the opportunity to diversify your plant palette. Embrace flowering perennials for vivid bursts of color. Similarly, fruit enthusiasts can consider apple, cherry, and pear trees that thrive in these zones. 

Winters are milder compared to higher elevations, but native plants still thrive in these areas as they do in the High Country. Look for plants that can adapt to occasional frosts and fluctuating temperatures, which are common in these areas, and prepare the soil to ensure good drainage and fertility.

Popular plants for the Foothills and Western Slope include: 

  • Blanket flower (Gaillardia aristata
  • Penstemon (Penstemon spp.)
  • Rabbitbrush (Chrysothamnus spp.)
  • Russian sage (Perovskia atriplicifolia)
  • Serviceberry (Amelanchier spp.)

Plants for Zone 7a (Front Range and Plains)

Along the Front Range and in the eastern plains, the relatively mild winters and longer growing seasons open up a world of possibilities. Grow a variety of vegetables like tomatoes, peppers, and lettuce. Additionally, explore a multitude of colorful annuals, such as petunias and marigolds, for vibrant flower beds.

Remember that microclimates within your zone can affect plant success, so pay attention to factors like sun exposure, soil quality, and local weather patterns. Consider plants that offer year-round interest, such as those with colorful foliage or attractive bark. Given the semi-arid climate, prioritize drought-resistant varieties and practice efficient water management.

Popular plants for the Front Range and Plains include: 

  • Flowering crabapple (Malus spp.)
  • Honey locust (Gleditsia triacanthos)
  • Marigold (Tagetes spp.)
  • Petunia (Petunia spp.)

7 Key to Keep Flowers, Shrubs, and Trees Alive in Colorado

Colorado’s diverse landscapes offer a breathtaking backdrop for gardens and landscapes, but they also present unique challenges. From the high-altitude chill of the Rockies to the semi-arid plains along the Front Range, maintaining the health and vitality of your greenery can be a demanding endeavor. Discover seven key ways to keep your landscape alive in the tough Colorado climate. 

Select the Correct Plants

One of the fundamental keys to a thriving landscape in Colorado is choosing the right plants for your specific USDA hardiness zone. Colorado’s diverse climate requires distinct plant adaptations. Consider factors such as native species, cold tolerance, drought resistance, and soil compatibility. By matching your plant choices to your zone and local conditions, you’ll set the foundation for a resilient and flourishing outdoor space that can withstand Colorado’s ever-changing weather.

Honey Locust tree in summer

Honey Locust trees grow well in the milder Front Range and Plains regions of Colorado.

©RussieseO/ via Getty Images

Water Properly

Water management is a critical aspect of maintaining a thriving landscape in Little London, where the climate can be both dry and unpredictable. Proper watering techniques are essential to ensure your plants receive the moisture they need without overwatering, which can lead to issues like root rot or mold growth.

From the arid plains to the mountainous terrain of the Rockies, follow some essential tips for proper watering: 

  • Understand your plants: Some plants thrive in well-drained soil with minimal moisture, while others need consistent watering. To water effectively, identify the specific needs of your plant species and group them accordingly in your landscape.
  • Be consistent: Establish a regular watering schedule to maintain soil moisture levels. Consistent watering helps your plants establish strong root systems and adapt to the climate. Be mindful of dry spells, as extended periods without rain can stress plants.
  • Water deeply: Soak the soil deeply to encourage deep root development. Plants with deep roots are better equipped to withstand drought and temperature fluctuations, and shallow watering can lead to vulnerable plants.
  • Water in the early morning: Water early in the morning to allow your plants to absorb moisture before the heat of the day. Avoid watering in the evening to prevent extended periods of wet foliage, which can promote fungal diseases.
  • Get the right tools: Drip irrigation and soaker hoses target the root zones of your plants efficiently. Avoid overhead sprinklers, which can waste water through evaporation and may wet plant foliage excessively.
  • Monitor your soil’s moisture: Check the moisture level of the soil around your plants regularly. Invest in a soil moisture meter or simply use your finger to determine if watering is needed. Adjust your watering schedule as the seasons change and rainfall varies.

Lay Mulch

Mulching is another vital component of successful gardening in Colorado. Applying mulch to your garden beds not only enhances their aesthetic appeal but also serves as a practical solution to combat the state’s dry spells, temperature fluctuations, and weed proliferation. 

Mulch is nature’s insulator and protector for your garden. It acts as a barrier between the soil and the environment, serving several essential functions. First and foremost, it helps retain moisture in the soil by reducing water evaporation, which is crucial in Colorado’s semi-arid regions. Additionally, mulch moderates soil temperatures, keeping roots cooler in the scorching sun and warmer during cold spells.

Weed Suppression

One of the significant advantages of mulch is its ability to suppress weed growth. Weeds can be particularly problematic in Colorado, where they compete with your plants for water and nutrients. Applying a layer of mulch inhibits weed germination and growth, saving you time and effort on maintenance.

Soil Health Improvement

Over time, organic mulches like wood chips, straw, or compost break down and enrich the soil. They contribute valuable nutrients to the earth, enhancing its fertility and structure. As mulch decomposes, it creates a healthier environment for your plants, promoting robust growth.

Follow a few simple steps to mulch your landscape: 

  • Prepare the soil: Ensure the soil is well-watered and free of weeds before mulching.
  • Choose the right mulch: Select a mulch type that suits your needs and aesthetics, whether it’s organic, inorganic, or a combination.
  • Lay the mulch: Spread a 2- to 4-inch layer of mulch evenly around your plants, taking care not to pile it against the plant’s base.
  • Maintain a gap: Leave a small gap around the base of trees and shrubs to prevent moisture and pests from accumulating.
  • Maintain your new mulch: Replenish organic mulch annually, as it naturally decomposes over time. Check the depth of your mulch layer each season and add more as necessary to maintain its effectiveness.

Improve the Soil

In Colorado’s varied landscapes, soil quality greatly influences the success of your garden or landscape. The state’s diverse climates, from arid plains to high mountain regions, present unique soil challenges that require careful attention.

Before embarking on any soil improvement endeavor, it is crucial to understand your soil’s composition and nutrient levels. Soil testing provides valuable insights into pH, nutrient content, and any deficiencies or imbalances. Armed with this information, you can make informed decisions about the necessary soil amendments.

Incorporate Organic Matter

Incorporating organic matter, such as compost or well-rotted manure, is a key strategy to enhance soil fertility and structure. These organic materials introduce essential nutrients, improve moisture retention, and encourage beneficial microbial activity in the soil. Apply a layer of organic matter and work it into the soil to a depth of several inches.

Adjust Your Soil’s pH

Colorado’s soils can vary in pH, affecting nutrient availability to plants. If your soil test indicates a pH imbalance, consider adding lime to raise pH or sulfur to lower it, depending on your specific needs. Adjusting pH ensures plants can access the nutrients they require for optimal growth.

Aerate Compacted Soil

To prevent soil compaction, avoid heavy machinery or foot traffic in planting areas. Compacted soil restricts root growth and inhibits the movement of water and nutrients. Use pathways or designated walkways to minimize soil disturbance. Additionally, core aerate your Colorado landscape annually to enhance airflow, improve water filtration, and increase nutrient availability. 

Control Soil Erosion

In Colorado’s regions with steep slopes or those prone to erosion, consider erosion control measures like planting ground-covering plants, installing retaining walls, or using erosion control fabrics. These measures protect the soil and also stabilize your landscape.

Embrace Native Species

One of the most effective and environmentally conscious strategies is to embrace native plant species. Native plants are naturally adapted to the local climate, soil, and wildlife, making them well-suited to thrive in Colorado’s diverse ecosystems. Furthermore, they are resilient to Colorado’s climatic extremes, from the hot and dry summers to winter’s freezing temperatures. 

Native plants require less maintenance and watering, reducing the need for irrigation. They also provide food and habitat for local wildlife, including birds, butterflies, and other pollinators. By planting native species, you can contribute to the preservation of the Centennial State’s unique biodiversity.

closeup chokecherry fruit

The Colorado native chokecherry tree reaches up to 30 feet tall and is an important source of nectar for pollinators.

©iStock.com/Elenakirey

These native species can add beauty and biodiversity to your garden while requiring less water and maintenance. Choosing native plants not only benefits your landscape but also contributes to the conservation of Colorado’s natural heritage.

  • Bigtooth maple (Acer grandidentatum)
  • Blanket flower (Gaillardia aristata)
  • Blue columbine (Aquilegia caerulea)
  • Chokecherry (Prunus virginiana)
  • Colorado blue spruce (Picea pungens)
  • Gambel oak (Quercus gambelii)
  • Indian paintbrush (Castilleja spp.)
  • Prairie coneflower (Ratibida columnifera)
  • Rocky Mountain penstemon (Penstemon strictus)
  • Serviceberry (Amelanchier alnifolia)

Protect Your Plants From Frost

Temperature fluctuations are common in the Highest State. Frost can occur unpredictably, even in the late spring and early fall, posing a threat to tender new growth and vulnerable plants. Understanding the average last frost date in your area is essential for planning your gardening activities. 

Colorado’s diverse geography results in varying frost dates across the state. Consult local gardening resources or the USDA Plant Hardiness Zone Map to determine when the last frost typically occurs in your region.

Choose Frost-Resistant Plants

Selecting naturally frost-resistant plant varieties can significantly reduce the risk of frost damage. Many native species and cold-hardy cultivars have evolved to withstand sudden temperature drops, making them excellent choices for Colorado gardens.

Cover Vulnerable Plants

When frost is in the forecast, cover your vulnerable plants with materials such as cloth, blankets, or frost blankets. These covers provide an insulating barrier that can trap heat and protect your plants from the cold. Be sure to remove the covers during the day to allow sunlight and air circulation.

Create Microclimates

Strategic garden planning can create microclimates that offer frost protection. Planting near walls, rocks, or structures can provide a warmer environment, while raised beds can help plants drain excess moisture, reducing the risk of frost damage.

Water Management

Proper watering practices can mitigate frost damage. Water your plants during the day, as wet soil retains heat more effectively than dry soil. Moist soil can also release heat at night, helping to moderate temperatures around your plants.

Plant Frost-Resistant Varieties

When selecting plants for your garden, prioritize species and varieties that are known for their frost resistance. Consult with local nurseries and gardening experts for recommendations tailored to your specific region within Colorado.

Popular frost-resistant varieties include: 

  • Blanket flower (Gaillardia aristata)
  • Blue avena grass (Helictotrichon sempervirens)
  • Blue flax (Linum perenne)
  • Columbine (Aquilegia spp.)
  • Common yarrow (Achillea millefolium)
  • Firecracker penstemon (Penstemon eatonii)
  • Fringed sage (Artemisia frigida)
  • Prairie coneflower (Ratibida columnifera)
  • Rocky Mountain penstemon (Penstemon strictus)
  • Russian sage (Perovskia atriplicifolia)
  • Silver sagebrush (Artemisia cana)
  • Soapweed yucca (Yucca glauca)
  • Wyoming big sagebrush (Artemisia tridentata)
  • Yellow coneflower (Echinacea paradoxa)
Yellow Coneflower Echinacea Paradoxa with a field of Yellow Coneflowers blurred in the background

Yellow coneflowers are drought-tolerant, cold-tolerant, and deer-resistant, making them a great choice for Colorado landscapes.

©Wanda Ann Solomon/Shutterstock.com

Maintain Your Landscape 

Once you’ve carefully selected the right plants, tended to the soil, and protected your garden from frost, the next crucial step is ongoing maintenance. Properly maintaining your landscape in Colorado ensures that your flowers, shrubs, and trees continue to thrive and flourish. 

Water Regularly

Consistent and appropriate watering remains a cornerstone of landscape maintenance in Colorado. Be attentive to the changing weather conditions and the specific water needs of your plants. Adjust your watering schedule as necessary, ensuring your plants receive the moisture they require without overwatering.

Pruning and Deadheading

Pruning and deadheading are essential tasks to promote healthy growth and vibrant blooms. Remove dead or spent flowers to encourage new growth and prevent disease. Prune shrubs and trees to maintain shape and remove dead or damaged branches.

Weed Control

Weeds can quickly take over your landscape, competing with your desired plants for nutrients and water. Regularly inspect and remove weeds from your garden beds to prevent them from becoming a nuisance.

Fertilization

Fertilize your plants as needed to provide essential nutrients for growth. Consider soil testing to determine specific nutrient requirements and select fertilizers accordingly. Follow recommended application rates to avoid over-fertilization.

Pest and Disease Management

Keep a watchful eye for signs of pests or diseases on your plants. Early detection and appropriate management are key to preventing the spread of issues that could harm your landscape.

Seasonal Care

Adapt your maintenance practices to the seasons. In spring, focus on soil preparation, planting, and addressing any winter damage. In summer, monitor watering and weed control. Fall is an ideal time for pruning, leaf removal, and preparing plants for winter. Lastly, winter maintenance may involve snow removal from walkways and protecting vulnerable plants from harsh conditions.

Master a Thriving Colorado Landscape

In the diverse landscapes of Colorado, creating and maintaining a vibrant landscape requires a blend of knowledge, strategy, and dedication. From selecting the right plants for your specific USDA hardiness zone to implementing proper watering techniques and embracing native species, the journey to a flourishing outdoor space is both rewarding and educational. 

Additionally, safeguarding your plants from the occasional frost and conducting regular maintenance rounds out the formula for success. By following the tips and strategies outlined in this guide, you can keep your flowers, shrubs, and trees alive but also watch them thrive and adapt to the ever-changing and awe-inspiring climate of the Centennial State.


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About the Author

Kimberly Magerl is a content writer and data analyst specializing in lawn and garden, home improvement, roofing, and solar technologies. She enjoys growing fruits and vegetables in her garden, getting outdoors, and putting her toes in the sand. A resident of Texas, when she isn't gardening, Kimberly enjoys trying new recipes and cooking with her home-grown herbs.

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