Kalanchoe plants are cherished for their vibrant, long-lasting flowers. A common frustration is when these plants fail to bloom. Understanding their specific needs helps diagnose and resolve this issue.
Kalanchoe Flowering Basics
Kalanchoes are “short-day plants,” meaning they require extended periods of uninterrupted darkness to initiate flower bud formation. This mimics their natural environment, where shorter daylight hours signal their blooming season, typically in winter or early spring. They need 12 to 14 hours of continuous darkness daily for six to eight weeks to stimulate flowering. Artificial light sources can easily disrupt this cycle.
Common Reasons Your Kalanchoe Isn’t Flowering
Insufficient Darkness
Inadequate darkness during bud formation is a primary reason Kalanchoes don’t flower. Even brief light interruptions, such as from a streetlamp or room light, disrupt the plant’s perception of “night” and prevent bloom initiation. Without consistent darkness, the plant’s internal clock for flowering is reset, leading to vegetative growth instead of flowers.
Incorrect Light Intensity
Both too little and too much light hinder Kalanchoe flowering. Insufficient light leads to weak, leggy growth, lacking energy for flowers. Conversely, excessive direct, intense sunlight stresses the plant, causing scorched leaves and reduced bud formation. Kalanchoes generally thrive in bright, indirect light.
Improper Watering
Watering practices significantly impact a Kalanchoe’s health and its ability to flower. Overwatering causes root rot, compromising nutrient uptake and vitality. When roots are damaged, the plant cannot support flower production. Conversely, prolonged underwatering also stresses the plant, causing wilting and inhibiting healthy growth necessary for blooming.
Unsuitable Temperatures
Extreme temperatures prevent Kalanchoe plants from flowering. If the environment is too hot, especially at night, it can disrupt metabolic processes and inhibit bud formation. Similarly, exposure to excessively cold temperatures, particularly below 50°F (10°C), stresses the plant and damages tissues, making it unable to produce blooms. Kalanchoes generally prefer moderate temperatures, with slightly cooler nights aiding in flower development.
Nutrient Imbalance
An imbalance of nutrients in the soil can direct the plant’s energy away from flowering. Too much nitrogen encourages lush, leafy growth at the expense of flower production. Conversely, a deficiency in phosphorus or potassium, crucial for flower and fruit development, directly hinders the plant’s ability to form buds and bloom.
Other Stress Factors
Several other factors can stress a Kalanchoe and prevent it from flowering. A root-bound plant struggles to absorb water and nutrients. Pest infestations, such as aphids or mealybugs, weaken the plant by feeding on its sap, diverting energy away from blooming. Very young plants might not be mature enough to flower, while very old plants may have reduced blooming capacity.
How to Encourage Kalanchoe to Bloom
Implementing a Dark Period
To encourage blooming, consistently provide 12 to 14 hours of uninterrupted darkness daily for six to eight weeks. Achieve this by placing the plant in a completely dark closet, under an opaque box, or inside a black garbage bag each evening. During the day, ensure the plant receives bright, indirect light for 10 to 12 hours. Maintaining this strict light and dark cycle is paramount for successful bud initiation.
Adjusting Light and Water
During its growing and flowering phases, provide your Kalanchoe with bright, indirect light for at least six hours a day. Avoid harsh, direct afternoon sun, which can scorch the leaves. Allow the top inch or two of soil to dry out completely between waterings. Water thoroughly until water drains from the bottom of the pot, then empty any excess water from the saucer to prevent root rot.
Optimizing Temperature
Maintain daytime temperatures for your Kalanchoe between 65°F and 80°F (18°C-27°C). Slightly cooler nighttime temperatures, ideally around 50°F to 60°F (10°C-15°C), can help stimulate flower bud development. Avoid placing the plant near drafts from open windows or heating/cooling vents, as sudden temperature fluctuations can stress it.
Fertilizing Properly
During the active growing season and when preparing for bloom, fertilize your Kalanchoe every two to four weeks with a balanced houseplant fertilizer, or one slightly higher in phosphorus. Dilute the fertilizer to half the strength recommended on the product label to prevent over-fertilization. Reduce or stop fertilizing during the dark treatment period and the plant’s resting phase.
Addressing General Plant Health
Regularly inspect your Kalanchoe for signs of pests and treat any infestations promptly. If the plant appears root-bound, repot it into a slightly larger container with fresh, well-draining potting mix. Ensure good air circulation around the plant to prevent fungal issues and promote overall vigor.
Post-Bloom Care for Continuous Flowering
Once your Kalanchoe has finished its flowering cycle, remove all spent flower stalks by pinching or cutting them back. This process, known as deadheading, encourages the plant to put its energy into producing new growth and subsequent blooms rather than forming seeds. After the blooming period, allow the plant to have a brief resting phase where you reduce watering and stop fertilizing for a few weeks. This period of rest prepares the plant for its next cycle of growth and flowering. Following this rest, you can then begin the dark treatment again to initiate a new round of flower bud formation.