Lavender, prized for its fragrant blossoms and silvery foliage, is a desirable herb for many gardeners in Colorado. Despite its Mediterranean origins, this semi-woody perennial can thrive in the high-altitude climate, but success depends on understanding its unique requirements. The region’s intense sunlight and low humidity are advantageous, yet the unpredictable weather and heavy native soils present specific challenges. Mastering the timing of planting and addressing the soil’s composition are paramount to establishing a healthy, long-lived lavender plant.
Optimal Planting Windows in Colorado
Colorado gardeners have two distinct periods for introducing lavender starts into the landscape. The most popular option is late spring, typically after the last hard frost, which usually falls between mid-May and early June. Planting during this window allows the young plant an entire growing season to establish a robust root system before the onset of the harsh freeze-thaw cycles of winter. For those new to growing lavender, the spring window is generally considered the safer bet.
The second viable option is planting in early fall, generally from late August through early September, giving the plant a minimum of six weeks before the ground freezes solid. Fall-planted lavender can sometimes establish more quickly and exhibit better survival rates, as the cooler temperatures reduce stress on the young plant. However, fall planting requires larger, well-rooted nursery stock, usually in four-inch pots or larger, to ensure they possess the necessary energy reserves to survive the coming cold.
Essential Soil and Site Preparation
Successful lavender cultivation begins with selecting a site that provides full, direct sunlight for at least six to eight hours each day. Lavender’s native environment is characterized by dry, rocky conditions, meaning the plant requires a location with exceptionally sharp drainage. Colorado’s native clay soils often retain too much moisture, which quickly leads to root rot, making soil amendment non-negotiable.
Amending heavy clay soil requires a strategic approach, as simply adding sand can create a dense, concrete-like mixture that worsens drainage. Instead, the soil structure should be improved by incorporating materials like coarse organic matter, such as bark mulch, or inorganic amendments like pea gravel, crushed granite, or limestone gravel. These materials create larger air pockets, which facilitate the rapid percolation of water away from the roots.
Lavender thrives in slightly alkaline soil, ideally with a pH range between 6.5 and 7.5, which is necessary for proper nutrient uptake. Gardeners should perform a soil test prior to planting to determine the existing pH level. If the soil is too acidic, incorporating agricultural lime or limestone gravel into the planting area will help raise the pH to the preferred range and contribute to better drainage simultaneously.
Best Lavender Varieties for High Altitude
Selecting the correct variety is fundamental for ensuring the plant’s long-term survival in Colorado’s cold, high-altitude winters. The most reliably hardy type is English Lavender (Lavandula angustifolia), which can tolerate temperatures down to USDA Hardiness Zone 4. This species is favored because it is the most resilient against the dramatic temperature fluctuations common to the region.
Specific cultivars like ‘Munstead’ and ‘Hidcote’ are recommended for their proven cold tolerance and compact growth habits. ‘Munstead’ is known for its reliability and ability to survive in Zone 4, while ‘Hidcote’ offers a deeper purple flower and slightly smaller stature. While Lavandins (Lavandula x intermedia), such as ‘Phenomenal,’ are also grown in Colorado, they are generally less cold-tolerant than the pure English varieties. French (L. dentata) and Spanish (L. stoechas) lavender are not cold-hardy and should only be cultivated as annuals or container plants.
Ensuring First-Year Survival and Winter Care
The first year is the most vulnerable period for a young lavender plant, and a focused watering regimen is important immediately after planting. For the first two weeks, the new plant should receive deep, infrequent watering to encourage the roots to grow downward. Once the plant is visibly established and new growth appears, the frequency should be sharply reduced, as overwatering is the most common cause of failure.
Preparing for winter is mandatory to protect the plant from extreme cold and desiccation. Once the plant enters dormancy, the primary concern is preventing repeated freeze-thaw cycles that can heave the plant out of the ground and damage the crown. A two to three-inch layer of rock or pea gravel mulch applied around the base is the best material, as it prevents soil moisture retention that leads to root rot. Organic mulches like wood chips are less suitable near the crown because they trap moisture and foster decay.
The dry, high-altitude air combined with intense winter sun and wind can quickly desiccate the plant’s evergreen foliage. To combat windburn, especially for young plants, a breathable fabric barrier, such as burlap or frost cloth, should be erected on the windward side or draped over the plant. Although lavender is dormant, the root zone should not be allowed to become completely dry, and supplemental watering should be provided during extended periods of winter drought.