Dahlias are celebrated for their vibrant colors and striking variety of forms, making them highly sought-after for flower arrangements and bouquets. Cutting dahlia blooms is necessary for maintaining the plant’s health and maximizing its flowering potential throughout the season. Understanding the specific techniques for harvesting and pruning ensures a steady supply of long-stemmed flowers while keeping the plant vigorous.
Harvesting Dahlias for Cut Flowers
The ideal time to harvest dahlia stems is in the early morning or late evening when the plant is fully hydrated and its sugar content is highest. Cutting during cooler parts of the day minimizes stress, which helps prolong the vase life. Dahlias will not open much further once cut, so select a bloom that is already almost fully open. The back petals should feel firm, and the bloom should not show signs of wilting or discoloration.
Use clean, sharp shears or snips to make a precise, angled cut. This angled cut increases the surface area for water absorption, which is beneficial for the hollow stems. For the longest, most usable stems, cut deep into the plant, often a foot or more below the bloom. Cutting deep encourages the plant to produce subsequent long stems.
Make the cut just above a leaf node, the slightly swollen joint where a pair of leaves emerges from the stem. New flowering stems will emerge from the two tiny growth buds located at this node. Cutting here effectively prunes the plant to branch out, increasing total flower production and ensuring long stems for arrangements.
Pruning and Deadheading for Garden Health
Pruning and deadheading focus on the long-term health and productivity of the dahlia plant. An early-season technique known as “pinching” encourages a bushier, stronger structure. This involves removing the central growing tip when the plant is about 10 to 12 inches tall and has three to five sets of leaves. Removing this tip stops vertical growth, forcing the plant to divert energy into lateral buds and develop multiple flowering stems.
Throughout the growing season, deadheading (the removal of spent flowers) is necessary to prevent the plant from wasting energy on seed production. Distinguish between a spent bloom and a developing flower bud. Spent blooms are generally soft and often have a flattened or pointed tip, whereas new, healthy buds are firmer, rounder, and more pointed.
To deadhead correctly, follow the stem of the spent flower down to the first strong set of leaves or an emerging side bud. Make the cut just above this point to eliminate the stub of the old stem, which can become a pathway for disease. This practice redirects the plant’s resources into the nearest strong growth point, promoting continuous flowering.
Essential Steps for Long-Lasting Blooms
The immediate treatment a dahlia receives after cutting directly relates to its vase life. Stems should be placed into a bucket of water immediately to prevent air bubbles from forming in the hollow stems, which block water uptake. Because dahlia stems are prone to bacterial growth, the bucket should be filled with clean water, ideally mixed with a commercial flower food solution.
Before arranging, strip all foliage that would sit below the water line in the vase. Submerged leaves quickly decay, creating bacteria that clog the stem’s vascular tissue and shorten the bloom’s life. After stripping the leaves, allow the stems to “condition” by resting in deep water in a cool, dark location for a minimum of a few hours.
Some growers recommend a hot water treatment, where the bottom inch of the freshly cut stem is briefly dipped into water heated to between 160°F and 180°F. This method helps clear blockages in the stem’s water-conducting vessels before transferring the stem to cool water for conditioning. Once arranged, change the vase water every other day, re-cutting a small portion of the stem each time to ensure maximum water absorption.