I would like to thank Lindsay Struthers for the following article. Lindsay is our Registrar, an ardent gardener, and an amazing volunteer. She and her family have done so much for our little community!
Why does everyone’s Christmas cactus flower but mine?
The Christmas cactus has a reputation of being challenging to get to re-bloom than an orchid, so how come everyone else has buds on their cactus but me?
The Schlumbergera bridgesii is commonly referred to as the Christmas cactus or holiday cactus because it blooms around American Thanksgiving through to Christmas. Calling this plant, a cactus is misleading because even though it is called a cactus it doesn’t like the growing conditions of an average cactus. It prefers humid conditions and does not like direct sunlight when grown outside, it also prefers more watering than most cacti. So, if I give my cactus all those things it most desires, why the heck don’t I get beautiful blooms at Christmas?
Well you, like me, might need to check how many hours of daylight your Christmas cactus is getting. While it is tempting to put these plants under a plant light with the rest of your high maintenance plants this might be the worst thing you can do for it. For a Christmas cactus to produce and set its blooms it needs 14 hours of undisturbed dark. A plant measures the amount of time spent in darkness with a chemical reaction that happens under the “skin”. Phytochrome is a plant pigment that takes red wavelengths produced by daylight and does a rapid conversion from its dark form to its light form. At night that process is reversed but the conversion from light form to dark form is done at a much slower rate. Your plant knows what time it is by comparing the amounts of light and dark form phytochrome. Because the conversion from light form to dark form occurs so quickly your 5-minute loo trip might be enough to convert more dark form phytochrome to light form phytochrome than your plant will be able to convert back before daylight comes in the morning. Now here is the interesting part, that internal watch your plant wears not only does the time, but it tells your plant the date as well… at least what month it is. As our seasons change from summer to winter the number of daylight hours decreases and those nighttime hours increase. Your plant knows that because as it has more dark form phytochrome available on a regular basis it must be closer to winter and therefore Christmas and that means time to get blooming. So, when summer is over, do yourself a favor and move that cactus to a less glamourous spot where it can have a good night’s sleep and you too will be rewarded with flowers at Christmas.
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