You either hate Kalanchoe diagremontiana or you love it. Or perhaps both simultaneously? I fall into the later category. Kalanchoe diagremontiana (from here on called K.d.) is one of the easiest succulents for a beginner to grow and propagate. It also has some very interesting flowers if you grow it well and let it get exposed to decreasing daylight hours of the winter. (It is called a short-day plant, that is flowering during the fall and winter as day length decreases.) At the same time, this plant, if not weeded out and removed from your “greenhouse” can easily take over.I was first introduced to this plant and began growing it in 1973. At that time, Kresge Department Stores (eventually to become K-Mart) often sold them at the cash register and in their plant section of the store. There would be a long hanging cardboard card with numerous small plastic bags pinned or clamped to the cardboard. You ripped a bag from the cardboard and paid for it at the cash register. Can’t remember exactly what they called them at the time, but the bag contained a single leaf with the instructions to safety pin the leaf to curtain in a sunny window of your house. The leaf would eventually sprout dozens of baby K.d.s which you could plant into soil containing pots.
Now you were in possession of this incredibly invasive but fascinating plant!
In the seventh grade of middle school, I volunteered to take care of the school’s greenhouse. As soon as I walked into the greenhouse for the first time, the whole greenhouse was completely grown over with K.d. They were quite large, 3 to 4 feet tall. The biology teacher had purchased some Venus flytraps and I had to make room for them in the greenhouse by ripping out some of the K.d. That was the first time I realized how easily this plant propagates itself even under the most severe neglect. (Nobody watered the plants all summer when students or teachers were not there.)
This plant grows up as an upright stalk with triangular dark green leaves that look like the head of an alligator (hence one of its common names) (See photo). The leaves can be up to about four inches long, and as I mentioned previously, the plant can get up to three to four feet tall. Especially two-year-old plants that are subjected to the natural decreasing daylight hours of late winter. Starting in the fall, these two-year-old plants begin to elongate and get taller. Then in the middle of winter they produce umbels of hanging pinkish to red tubular flowers. (See photo) If you have different clones of this plant (rarely you do) then these flowers could get pollinated to produce seed.
The seed, like other Kalanchoe species, is very tiny, almost dust-like. I have never grown the plant from seed. The usual mode of reproduction of this plant is via tiny baby plants that appear on small nodes along the leaf margins. There are many other Kalanchoe species which also propagate or reproduce this way. These tiny baby plants are clones of the parent. They grow several tiny roundish leaves and begin to put out small hairs of roots. If anything brushes or bumps into the plant the babies are dislodged from their nodes and fall to the ground. They quickly root and take off growing. In no time there are dense stands of this plant.
This species is originally from Madagascar where there are many other species of Kalanchoe. The plant has been distributed as an ornamental in many countries due to its interesting habits. In warm subtropical or tropical areas, they can establish outdoors and become invasive. They have escaped gardens in States like Florida. K.d. is very susceptible to frost so it is never established in northern areas that are subject to any freezing.
This plant is amazingly easy to grow for succulent enthusiasts. If you furnish it with plenty of light and remember to water it once in a while it will flourish. It is amazingly free of pest and diseases. Usually, the only problem I’ve seen is, they can get powdery mildew with inadequate light and ventilation (stagnant air). Powdery mildew will grow as a fine grey dust in circular spots on the leaves. If this happens it’s a sign you need to supply more illumination and increase ventilation. The mildew spots will sometimes be callous and heal over leaving unsightly brown corky spots on the leaves.
A while back I encountered another problem on my K.d.s. I had several of them develop curly and deformed leaves and stems. The damage was reminiscent of other succulents when they get infected by burrowing mites. I really didn’t care if they had mites since I have many plants and if the mites didn’t spread to my other plants. I eventually sprayed with systemics for mites anyway, but this didn’t take care of the problem. Then somewhere doing a literature search I found a reference that said these K.d.s are subject to deformities if they have nutrient deficiencies. I quickly found out that the deformed plants were simply not getting enough nutrients (fertilizer). Fertilizer applications seem to have taken care of the problem.Another reason for this plant’s success and invasiveness is it contains bufadienolide cardiac glycoside poisons, one of which is called diagremontianin. These toxins are very poisonous to cattle that might graze on this plant in semi-desert environments. This poison is probably why you don’t see animals and perhaps insects feeding on it. Slugs can be an intermittent problem in my greenhouse, but they never touch the K.d.s. Perhaps because of this toxin. So, if you have animals in your house like cats or dogs that like to dine on your plants, this may be one to avoid. Although I’ve never known anybody to report a problem with their animals from eating this plant. In fact, at one time I heard that land tortoises like to feed on it. Perhaps tortoises are immune to the bufadienolide cardiac glycosides?
With how easily this plant reproduces and propagates it begs the question, “Why doesn’t it take over in places where it grows”. Why doesn’t K.d. take over the subtropical and tropical world? Even though this plant is very aggressive colonizer in dry areas, I read it is a very poor competitor in areas that get enough rainfall to allow grass to grow. Seems that grass is K.d.s mortal enemy. If you like this plant a very close relative, Kalanchoe tubiflora, has similar growth and habits except its leaves are much smaller and simply spindle shaped or tubular. The baby Kalanchoe tubiflora grow only at nodes at the tip of this species’ leaves. Much less fecund that K.d. Sometimes these two species hybridize via cross pollination of their flowers and if you grow them from seed. Leading to plants that are intermediate in appearance between the two species. Older references placed these two plants in genus Bryophyllum. So, you may see them in these books listed under this genus rather than Kalanchoe. Another very popular Kalanchoe is Kalanchoe blossfelldianum. Commonly called Flaming Katy, Florist Kalanchoe or Christmas Kalanchoe. This species is sold as a wintertime or Christmas flower in many garden centers. It comes in many blossom colors such as red, yellow, and orange. This Kalanchoe does not reproduce by tiny babies growing at nodes. It is propagated by stem and leaf cuttings and by seed.
I hate K.d. because I must get into my greenhouse and weed them out. However, I also love them because they are so easy to grow, propagate so easily, and because they are obviously a well-adapted plant fit for survival.
The genus Kalanchoe has a huge number of very diverse and fascinating species (estimated to be 125).Enough to keep a succulent enthusiast busy collecting ever more interesting species of this genus. I would collect different Kalanchoes if it wasn’t for the fact, I already grow more cacti than succulents. I just need to get into my greenhouse to weed out the ever-present K.d.s that are always threatening to take over! – Doug Sweet