Bamboo, technically a woody grass, can be cultivated in Colorado, but success requires deliberate choices and specialized management. The semi-arid climate and extreme temperature swings of the Rocky Mountain region require selecting varieties with high cold tolerance. Growing bamboo requires planting specific cold-hardy cultivars and implementing strict winter protection measures.
Choosing Cold Hardy Species
Selecting the right species is the most important factor for success in Colorado’s USDA Hardiness Zones 4 and 5. Bamboo is categorized into clumping and running types, which influences cold hardiness and garden management. Clumping varieties, primarily from the genus Fargesia, are ideal for smaller gardens because they spread slowly and predictably, expanding their root mass outward.
Fargesia species, such as Fargesia murielae and F. nitida, are highly cold-tolerant, surviving root temperatures down to approximately -20 degrees Fahrenheit. Fargesia rufa is another excellent clumping choice, tolerating temperatures near -15 degrees Fahrenheit and valued for its dense, bushy growth habit. These clumpers are well-adapted to the sharp temperature drops common in Colorado’s high-altitude environment.
Running bamboos, from the genus Phyllostachys, are available in hardy varieties but require containment. Phyllostachys bissetii is robust, hardy to at least -10 degrees Fahrenheit, and can survive lower temperatures with adequate root insulation. Phyllostachys nuda is another reliable runner, highly rated for its cold tolerance and ability to thrive in Zone 4 conditions. These runners allow for taller growth, but their aggressive underground spread must be addressed during planting.
Essential Care for Colorado Winters
The most significant threat to bamboo in Colorado is desiccation, caused by extreme cold, high altitude, and intense winter sun and wind. Winter desiccation, or leaf burn, occurs when leaves lose moisture to the dry air faster than the frozen roots can replace it. This process quickly turns evergreen foliage brown and damages the exposed culms.
Preparing the plant for winter involves ensuring maximum moisture retention before the ground freezes solid. Gardeners should perform deep watering late into the fall, continuing until the soil is no longer receptive to water. This practice saturates the root zone, providing a moisture reservoir for the plant to draw upon during winter.
Protecting the rhizomes, the underground stems, is necessary for long-term survival. Applying a thick, four-to-six-inch layer of organic mulch, such as wood chips or straw, over the root zone insulates the soil. This mulch layer helps moderate soil temperatures and prevents shallow rhizomes from freezing solid during deep cold snaps. Planting the bamboo in a location protected from harsh north or west winter winds will also significantly reduce the risk of foliage burn.
Controlling Spread and Planting Techniques
Successful cultivation begins with proper site selection and soil preparation to manage the plant’s growth pattern. Most bamboos prefer a site with plenty of sunlight but some afternoon shade, which mitigates the intensity of Colorado’s high-altitude sun. Since native soil often contains heavy clay and can be alkaline, the planting hole should be heavily amended with organic compost to improve drainage and nutrient availability.
For any running variety, installing a proper root barrier is non-negotiable to prevent invasion of the landscape. This barrier should be made of durable, high-density polyethylene (HDPE) material, typically 60 to 80 mil thick, strong enough to resist puncture. The barrier must be buried at least 28 to 30 inches deep to block the downward-spreading rhizomes.
The barrier must extend approximately two inches above the soil line to prevent rhizomes from growing up and over the top edge. The ends of the barrier must be overlapped and securely fastened to create a continuous ring of containment around the planting area. For clumping types, a root barrier is unnecessary, but ensuring proper drainage in the amended soil remains a priority for all bamboo species.