The practice of “forcing” dormant branches is a simple, rewarding technique that coaxes woody plants to bloom indoors weeks ahead of their natural schedule by introducing them to the warmth and moisture of an indoor environment. Forsythia is widely considered one of the easiest and most reliable shrubs for forcing, making it an excellent choice for introducing vibrant yellow color to the home during late winter.
Timing and Selecting Branches
The success of forcing blooms hinges on harvesting the branches after the shrub has fulfilled its necessary chilling requirement. This cold period, which breaks the plant’s dormancy, is typically completed by late January or early February. Cutting branches too early, before adequate cold exposure, will result in buds that fail to open. The ideal window for cutting generally runs from late January through March.
When selecting cuttings, focus on healthy, mature stems that are approximately pencil-thick, or about a half-inch in diameter. Distinguish between flower buds and leaf buds, as only flower buds will produce the desired yellow blossoms. Flower buds are noticeably rounder and plumper, while leaf buds are smaller and more pointed along the stem. Use sharp bypass pruners to make a clean, angled cut, which maximizes the surface area for water absorption.
Conditioning the Cuttings
Immediately after harvesting, the woody stems require preparation to ensure they can efficiently absorb water. Since the bark and woody tissue impede water uptake, the bottom few inches of the stem must be altered. For thicker branches, gently crush the stem ends with a hammer to loosen the fibers and create more pathways for moisture. Alternatively, make several vertical slits, about one to two inches long, in the base of the stem with a sharp knife.
Once conditioned, place the branches into a deep bucket of warm water, which helps to gently break the remaining dormancy. Strip any buds or small side twigs from the portion of the stem that will sit beneath the water line to prevent decay and fouling the water. Allow the cuttings to soak for several hours or overnight in a cool, dark location, such as a basement or garage, to fully hydrate before moving them to their final display vase.
Water and Environment for Blooming
To encourage the dormant buds to swell and open, the branches should initially be kept in a cool location, ideally with temperatures around 60°F. During this stage, the branches do not require bright light, so placing them away from direct sunlight and drafts is beneficial. This cool, stable environment prevents the buds from developing too quickly, which can lead to weak, short-lived blooms.
Maintaining a high level of moisture is necessary throughout the forcing process. The branches must be misted daily with water, as dry indoor air can cause the delicate flower buds to shrivel before opening. Change the water in the vase every two to three days to inhibit the growth of bacteria and fungi, which can clog the vascular system. Once the buds begin to swell and show the first hints of yellow color (typically after one to two weeks), the branches can be moved to a brighter, warmer spot for display. Full bloom usually occurs within two to four weeks of the initial cutting; move the vase back to a cooler location overnight to extend the life of the flowers.