Kalanchoe, a vibrant succulent, typically bursts into color during the winter and early spring months. These plants are popular for their dense clusters of small, brightly colored flowers. While the natural bloom cycle aligns with shorter days, it is possible to manipulate the environmental conditions to achieve spectacular summer flowering. By understanding the plant’s biological needs and implementing a specific light regimen, you can successfully “trick” your Kalanchoe into blooming during the summer season.
Understanding the Natural Kalanchoe Bloom Cycle
The Kalanchoe plant is classified as a photoperiodic or “short-day” plant, meaning its flowering is directly controlled by the relative length of the day and night. For these plants to initiate the growth of flower buds, they require a specific duration of uninterrupted darkness. This requirement is a biological trigger that signals the plant to prepare for blooming.
The necessary dark period is between 12 and 14 hours every 24-hour cycle to stimulate the production of flowering hormones. Naturally, the long daylight hours of summer, which can extend to 15 or more hours in some regions, actively prevent this hormonal shift. This explains why the plant typically waits until the long nights of late fall and winter to begin its natural display. The key to summer blooming is artificially creating those long nights.
Implementing the Critical Light Manipulation
To force a summer bloom, you must begin a rigorous “dark treatment” period that mimics the light conditions of winter. The goal is to provide 12 to 14 hours of absolute, uninterrupted darkness every day for six to eight weeks. This consistent long night is necessary for the plant to produce the phytohormones that initiate bud formation.
A practical way to achieve this is by placing the plant in a completely dark space, such as a closet, a basement, or under a large cardboard box, every evening. For example, you could move the plant to its dark location at 5:00 PM and return it to bright light at 7:00 AM the following morning. Crucially, the darkness must be total; even brief exposure to artificial light can interrupt the photoperiodic cycle and restart the entire six-week process.
During the remaining 10 to 12 hours of the day, the plant still requires bright, indirect sunlight to carry out photosynthesis and generate the energy needed for future flowers. This light manipulation must be maintained daily until you observe the initial formation of small flower buds at the tips of the stems. Once buds are clearly visible, typically after six to eight weeks, the dark treatment can be stopped, and the plant can be returned to its normal, bright location to allow the buds to mature.
Essential Care for Successful Summer Flowering
While light manipulation is the primary driver for blooming, proper maintenance ensures the buds develop and the flowers last. During the six-to-eight-week dark treatment, you should slightly reduce the frequency of watering. As a succulent, the Kalanchoe stores water in its fleshy leaves and does not require as much moisture when its growth is intentionally slowed.
Once the flower buds appear, you can resume a more regular watering schedule, allowing the top inch or two of soil to dry out between waterings. At this point, introducing a balanced fertilizer that is higher in phosphorus can provide the necessary nutrients to support the bloom. A fertilizer with a formula like 0-10-10 or a similar high-phosphorus ratio will specifically encourage flower development rather than just foliage growth.
Maintaining a stable environment is also important for longevity; Kalanchoe flowers last longest in cooler temperatures, ideally between 65°F and 75°F during the day. While summer heat can be intense, keeping the plant away from direct afternoon sun and intense heat will prolong the life of the vibrant summer blooms.