Artichokes are typically grown as perennials in mild, coastal climates like California. However, it is possible to cultivate them successfully in Colorado. Due to the state’s shorter, cooler growing period, the globe artichoke must be treated as an annual vegetable crop. Gardeners must employ specific techniques to encourage the plant to produce its edible flower bud in a single season.
Adapting to Colorado’s Short Growing Season
The primary challenge for growing artichokes in Colorado (USDA Hardiness Zones 3 through 6) is the severe winter cold that kills the perennial root crown. To overcome this, gardeners must select annual varieties, such as ‘Imperial Star’ or ‘Colorado Star,’ and start them indoors 10 to 12 weeks before the anticipated outdoor transplanting date. This gives the plants a significant head start on the growing season.
The successful production of the edible bud relies on a specific biological process called vernalization, which is the exposure of the plant to cold temperatures to initiate flowering. For artichokes grown as annuals, this chilling period must be artificially induced after the seedlings have developed four true leaves. The young plants need to be exposed to temperatures between 45°F and 50°F for approximately 10 consecutive days to trick them into believing they have survived a winter.
The vernalization process is completed by placing seedlings outdoors in a protected area or cold frame during a cool spring stretch, ensuring temperatures remain above 32°F. After this chilling treatment, transplants are ready for the garden once the danger of the last hard frost has passed. Managing this indoor start and cold exposure condenses the plant’s two-year perennial cycle into one productive season. This timing ensures the plants are mature enough to form flower buds during the summer heat.
Essential Soil and Sunlight Requirements
Once the vernalized seedlings are moved outside, they require a specific environment to sustain rapid growth. Artichokes are heavy feeders and perform best in soil that is rich, deep, and amended with organic matter like compost or aged manure. The ideal soil should be a well-draining sandy loam to prevent root rot, which occurs if the crown remains waterlogged.
A slightly acidic to neutral pH, ranging from 6.0 to 7.0, supports optimal nutrient uptake for the maturing plant. The intense, high-altitude Colorado sun is beneficial, and artichokes need a location that receives a minimum of six hours of direct sunlight each day. This exposure is necessary for the robust vegetative growth that precedes bud formation.
Consistent and deep watering is important in Colorado’s typically dry climate to support the plant’s large foliage and the development of tender buds. Gardeners should aim for deep saturation without allowing the roots to sit in standing water. Applying a thick layer of organic mulch around the plants helps to retain soil moisture and keeps the root zone cooler during the peak summer heat.
Harvesting and End-of-Season Care
The reward for early-season management arrives in late summer or early fall, typically 85 to 100 days after transplanting. Artichoke buds are ready for harvest when they are tight and firm, before the scales or bracts begin to pull away from the center. Harvesting the central bud first encourages the plant to produce smaller, secondary buds on the side shoots.
To harvest, the stem is cut about one inch below the base of the bud with a clean, sharp knife. If the scales begin to open and reveal the purple flower, the bud has passed its edible stage and should be left on the plant to bloom as a purple thistle flower. Once the growing season concludes with the first hard frost, the plant will die back to the ground as a natural end to its annual cycle.
In Colorado’s warmer microclimates, such as the Western Slope, gardeners may attempt to overwinter the perennial crown. This involves cutting the plant back to about six inches above the soil line and covering the crown with a thick layer of organic mulch, such as straw or leaves, for insulation. However, this is a risky endeavor, as the deep, prolonged freezes of a typical Colorado winter often result in the death of the crown.