The dahlia is a vibrant flower prized for its varied forms and colors. Dahlias are prime examples of “cut and come again” flowers, meaning harvesting a bloom encourages the plant to produce many more throughout the growing season. This characteristic makes them a favorite for flower farmers and home gardeners aiming for a continuous supply of fresh blossoms. Consistent harvesting is beneficial because it stimulates the plant’s regenerative ability.
Understanding the “Cut and Come Again” Mechanism
The plant’s ability to regenerate flowers after cutting is rooted in a natural biological process known as the redirection of energy. When a plant produces a flower, its primary biological goal is to create seeds for reproduction. Removing the spent or mature bloom prevents the plant from expending energy on this seed production, effectively signaling the need to create new flowers.
A specific detail involves the removal of the terminal bud, the main flower bud located at the tip of the stem. This bud exerts hormonal control over the rest of the stem, a phenomenon called apical dominance. Apical dominance suppresses the growth of smaller, dormant lateral buds located lower down the stem, favoring the growth of the single main stem.
When the terminal bud is removed during harvesting, the suppression is lifted, and the plant’s energy is redirected to the nearest lateral buds. These newly stimulated buds then develop into side shoots, which grow into new stems capable of producing more flowers. This response not only increases the total number of blooms but also encourages a bushier growth habit, resulting in a healthier, more robust plant that yields more stems throughout the season.
The Essential Cutting Technique for Continuous Regrowth
Maximizing the dahlia’s cut and come again potential requires a specific cutting technique that stimulates the dormant lateral buds. When harvesting a flower for a vase, the goal is to cut a long, usable stem, which means going much deeper into the plant than simply clipping off the flower head. This deep cut is what acts as a strong signal to the plant to produce new growth.
The cut should be made just above a leaf node, which is the point on the stem where a pair of leaves or a new shoot emerges. Look down the stem of the flower you wish to harvest until you find a strong, outward-facing lateral bud or a pair of buds. Cutting directly above this node ensures that the new growth point is primed to take over and produce a new flowering stem.
A common mistake is simply deadheading, which involves removing only the spent bloom just below the flower head. True harvesting, or “deep cutting,” requires sacrificing a significant portion of the stem (often 14 to 18 inches) to ensure the next set of shoots is vigorous. Always ensure that at least two sets of leaves remain on the main stalk below the harvest point, as this foliage is necessary for photosynthesis to power the new growth.
Seasonal Maintenance for Extended Blooming
After implementing the proper cutting technique, ongoing care is necessary to fuel the continuous production of new blooms. Dahlias are heavy feeders, requiring consistent nutrient replenishment to sustain rapid growth and flower development. Once the plants begin blooming, switch to a low-nitrogen fertilizer blend (such as a 5-10-10 or 10-20-20 formula) to promote flower production over excessive leafy growth. Apply this fertilizer monthly, starting when the first sprouts appear and continuing until early autumn. Consistent, deep watering is also important for these high-performing plants, especially during hot, dry periods.
Dahlias need about one inch of water per week. Deep watering, reaching 8 to 10 inches into the soil, is preferred over light surface sprinkling, as it encourages roots to grow downward and makes the plant more resilient to heat stress. Finally, staking or supporting the plants is necessary, particularly for taller varieties, because continuous cutting leads to abundant, heavy growth. Place sturdy stakes or netting around the plants early in the season to prevent flower-laden stems from bending or breaking in high winds or heavy rain.