BALFOUR  GREENHOUSES

Only 25 years ago Kalanchoe were grown almost exclusively as a christmas holiday crop, but intensive breeding efforts by Dutch and Danish companies have resulted in a large assortment of vastly improved brightly colored varieties for year-round production. On European markets Kalanchoe have been the dominant flowering potted plants for almost a decade. No surprise to us; Few flowering potted plants offer the same decorative value and lasting qualities as Kalanchoe blossfeldiana Hybrids.

Other Kalanchoe species produced commercially in smaller numbers are K. tomentosa, K. laxiflora, and the former genus Bryophyllum with the species K. daigremontiana and K. tubiflora. Most of the species originate in relatively cool mountain regions in Madagaskar, but some creeping or trailing forms were found in tropical rain forests in southeast Asia and Brazil. Many of these unusual species have been bred into the varieties of our current assortment of Kalanchoe Hybrids.

For potting we recommend a peat based, well aerated substrate that drains freely. We recommend a mix of peat with about 30% perlite. The peat should be physically stable to maintain its structure throughout the crop cycle. The pH should be adjusted between 5.5 and 6.0.

Throughout the crop cycle, the growing medium should be kept uniformly moist. The root system of Kalanchoe is very sensitive. Root damage occurs quickly if the soil conditions are constantly too wet or if the soil dries out too much. The plants are very drought resistant and it takes a long time before they start to wilt, which makes it hard to see if a pot needs water. But growth will come to a halt and leaves will discolor irreversibly if plants get too dry.

Kalanchoe are short-day plants. Flowering is induced by exposing the plants to less than 11 hours of daylight. Plants stay vegetative with daylenghts of more than 13 hours. Blackout for flower induction has to be applied continuously every day for the first 7-9 weeks after the start of blackout. After the flower buds are visible, the plants can be exposed to long days, but the quality of most cultivars will improve if blackout is applied until marketing. Lighting for night interuption requires a minimum of 20 W/m² installed light bulbs.

Kalanchoe require relatively high light levels throughout the cultivation cycle. Dark weather results in slow growth and in poor shoot formation. Assimilation lighting during winter is very beneficial. Excessive light levels in summer will cause discoloration of the foliage and fading of the flower colours. Moderate shading should be applied with radiation levels of more than 500 W/m².

Temperature control during the entire cultivation should aim at 19°-20°C constant during day and night. Good control during the short day period is essential. Average temperatures of more than 23°C can result in flower delay or bud abortion and in other growth distortions. Temperatures of less than 16°C can completely inhibit flower development. Temperatures of 16°-18°C will delay flowering.

The control of relative humidity is important but difficult in Kalanchoe cultivation. As CAM plants, Kalanchoe reduce the evaporation of water during bright days. At the same time it is necessary to ventilate the greenhouses for temperature control. This can cause the relative humidity to drop far below 50%. The performance of the plants in these situations is greatly improved if additional moisture can be brought into the greenhouse. High relative humidities above 90% can cause severe flower damage and disease problems.

Kalanchoe are members of the Crassulaceae family and as such are CAM plants. Their stomata of open during nights when relative humidities are higher, and they are closed during days to reduce water loss in the arid conditions to which the plants are native. CO2 for photosynthesis is absorbed during the night. In modern Hybrid Kalanchoe this mechanism is somwhat altered. The plants react well to CO2 enrichment during the day, as long as the relative humidity in the greenhouse is reasonably high.

Last updated on January 3, 1998. Page designed by Albert Grimm