Double the Fun with Calandiva Kalanchoes

The Christmas kalanchoe or flaming Katy (Kalanchoe blossfeldiana) is a traditional Christmas plant, in culture for over 100 years. It is a succulent native to Madagascar bearing fleshy leaves with a waxy sheen and serrated margins. The leaves are dark green, sometimes with a red border when the plant receives full sun. However, its most striking feature is its bloom: each plant bursts into a dense mass of bright red flowers with four fleshy petals at the beginning of winter. And the flowers last a long time, usually at least six weeks. The Christmas kalanchoe is one of those plants that really does adapt well to the growing conditions in the average home and thus makes an excellent houseplant.

For generations though, the Christmas kalanchoe was offered in exactly one color, bright red. Then in the 1980s, Dutch hybridizers began to introduce other colors: orange, pink, purple, white, etc. and these are now certainly as common in garden centers as the original red.

Another fairly recent innovation is that growers learned to extend the selling season throughout the entire year. Thus, suppliers are dropping the old name, Christmas kalanchoe in favor of calling it “decorative Kalanchoe”, since you have as much chance of finding one in spring, summer or fall as at Christmas.

A Diva is Born!

Throughout the first 100 years of kalanchoe culture, all kalanchoes had four-petaled flowers. Then in 1998, a Swedish retailer of kalanchoes reported to his supplier that he had found a curious specimen in a lot of plants of ‘Bromo’, a cultivar with purple flowers. Instead of the normal four petals, this mutation had 32 petals, forming a small rose. The flower was not just double: you could almost call it octuple!

 

This mutation was launched as a cultivar under the name ‘Leonardo’ and was at the origin of a major hybridizing program, leading in 2002 to the launching of a new series of fully double kalanchoes, Calandiva®. Six cultivars were introduced the first year, but others followed and now the series includes 50 cultivars in different shades of red, pink, orange, purple and white, although only 25 are still listed in the catalog of the Dutch supplier. Calandivas took the indoor gardening world by storm and are are now the best selling kalanchoes in the world.

A second series with larger flowers just been launched, Grandiva®. There are currently only five cultivars Grandiva, but other cultivars are sure to follow.

Making Their Bloom Last

Calandiva kalanchoes are available all year round, not just at Christmas. When you buy them, they are compact plants forming a dense rosette whose center is entirely hidden by flowers. The flowers are not only gorgeous, but they remain in bloom 6 weeks or more… and the plant only requires minimal care.

That’s because Christmas kalanchoes are succulents, accustomed to tough conditions. You don’t need much in the way of growing experience to keep them alive. In fact, all you really need to know about keeping them blooming is to water them thoroughly, but only when the soil is dry to the touch. Otherwise, for those 6 or so weeks when they bloom, you can put them anywhere, from full sun to almost total shade and give them any temperature from 60 to 80?F (16-27?C).

After they stop blooming, just toss them in the compost… or at least that’s what suppliers hope you’ll do. Wouldn’t it be tragic if people began to keep their Calandiva kalanchoes from one year to the next rather than buying new ones?

Making Calandivas Bloom Again

If you want to break out of the box and get your Calandiva Kalanchoe to rebloom, here’s what to do. Do note thought that If you can do almost anything with a Calandiva while it is in bloom, if you want it to flower again, you’ll have to start giving it much more appropriate conditions.

Start by cutting off its faded flowers, then place it in front of a brightly lit window, the closer to full sun the better. Keep watering it thoroughly, then letting it dry out almost completely before watering again. Also, add a pinch of fertilizer from time to time. If your plant starts to stretch (a sign it’s not getting enough light, by the way), don’t hesitate to cut it back to stimulate more compact growth.

During the summer, you can even acclimate your plant to outdoor conditions and grow it there in full sun as long as you remember to bring it back indoors again before the nights begin to cool, at the end of August or in early September in most areas of the Northern Hemisphere.

The most important step in getting your plant to bloom in time for Christmas has to be put into effect in late September. Stop pruning and fertilizing it and, even more importantly, place the plant in a room that is dark at night but where it will get full sun during the day. No extraneous evening light must reach it at night for the next few weeks, because it’s a short day plant: days of less than 12 hours are absolutely necessary to get the plant to bloom. In the Northern Hemisphere, days will naturally be shorter than 12 hours from September 22 on.

Note that the average living room or kitchen might not be appropriate: if you turn on lights in the room at night, this will stop the plant from blooming. Instead, put the plant in a room you don’t illuminate at night (a guest room, for example) or install a cardboard barrier between the sunny windowsill and the lighted room beyond.

Under this regime of short days, long nights and regular watering, the plant will start to bloom all on its own come November or December. And you can repeat this treatment every year.

For readers who live in zones 9 and up, Calandiva kalanchoes can also be grown outdoors in well-drained soil and will bloom naturally… as long as you live at least a bit north or south of the Equator. That’s because days need to be at least a little less than 12 hours long for the plant to rebloom and they are exactly 12 hours long all year long on the Equator.

Getting Your Calandiva to Flower at Any Season

But if Calandivas naturally bloom around Christmas, how is it that you see them on sale, in full bloom, all year long, even in summer when days are very long? That’s because the grower “forced” them by giving them short days. That’s simple enough to do in a greenhouse: simply pull a black cloth over plants for 14 hours at night and give it full sun during the day. You can do pretty much the same thing in the average home.

About 3 months before you want your Calandiva to bloom, place the plant under a 2- or 4-tube fluorescent lamp (4 tubes, is better). Add a timer and set it so the plant gets 10 hours of light per day. It must receive no outside light beyond the 10 hours required, so it would be wise to place the lamp in a closet or to surround it with black cloth. When you see flower buds appear, which takes about 4-6 weeks, you can put the plant back near a window and give it natural lighting again. That’s because once the buds are initiated, short days are no longer required and it will bloom without any special care. You can even get the same plant to bloom twice a year by repeating short days after it has started to put on new growth.

Just Ignore the Label

You’ll often see a note on Calandiva kalanchoe labels that says multiplying the plant is illegal. This is what the supplier wants you to believe, but in fact, this ban on multiplication only applies to professionals who want to reproduce it for resale. If you want to, you can take as many cuttings of Calandiva kalanchoes as you want… as long as you don’t sell the extras at the flea market!

Good luck with this new houseplant diva! You’ll soon discover she is no prima donna, but a most compliant soloist who’ll give an outstanding performance year after year!