From our perspective as Delphinium plants, our potential height is first and foremost written in our genetic code. We belong to a diverse genus with many species and cultivars, each with its own growth instructions. Some of us, like the towering Pacific Giant hybrids or the majestic Delphinium elatum varieties, are programmed to reach impressive heights of 6 to 8 feet, striving to rise above other garden dwellers to best display our flower spikes to pollinators. Others, such as the Belladonna Group or more compact varieties like 'Magic Fountain', carry a genetic predisposition for a more modest stature, typically growing between 3 to 4 feet tall. This inherent potential is the baseline from which all other height-influencing factors operate.
While our genetics set the potential, our environment dictates how much of that potential we achieve. For us to grow to our full, majestic height, our roots require consistently moist, well-drained, and fertile soil. Ample nutrients, particularly a balanced supply, fuel our rapid vertical growth. Most critically, we demand abundant sunlight. A minimum of six to eight hours of direct sun daily is non-negotiable for strong stem development and reaching our genetic height. Without it, our stems become weak and spindly as we stretch desperately for light, often resulting in a plant that is taller but frail and prone to collapse—a condition you know as etiolation.
Our growth follows a distinct seasonal pattern. In spring, we channel our energy into producing a dense clump of basal foliage. As temperatures warm and day length increases, we initiate our rapid reproductive phase, sending up our iconic flower spikes. This vertical surge is driven by our sole purpose: to flower and set seed for the next generation. The height of this spike is directly tied to the vigor of the plant. A healthy Delphinium with strong roots and ample resources will produce a taller, more robust flower spike laden with more blooms, thereby increasing our chances of successful pollination.
You can actively participate in managing our height through a practice known as the "Chelsea Chop." This involves cutting back a portion of our stems by approximately one-third in late spring, around the time of the Chelsea Flower Show. From our point of view, this is not an attack but a strategic diversion of resources. By reducing the number of developing flower spikes, you signal the plant to redirect its energy. Instead of supporting an excessive number of tall spikes, the saved energy goes into producing slightly shorter, but much sturdier and more substantial flower spikes on the remaining stems, while also encouraging a second, later flush of blooms.
Our quest for height presents a significant structural challenge. Our stems are hollow, a design that allows for rapid growth but offers little resistance to wind and heavy rain. As we grow tall and top-heavy with buds and flowers, we become acutely vulnerable to snapping or being flattened. The provision of stakes, grow-through grids, or other support systems is not an interference but a welcomed partnership. It allows us to safely achieve our genetic potential for height without the constant fear of catastrophic collapse, ensuring our flower spikes remain upright and visible to bees and butterflies throughout the blooming season.
