Today in the Garden of a Lifetime: Mountain Cabbage Tree

Cussonia paniculata overall 061816 640


A ten-foot cabbage tree can be too tall even for a plant geek, especially when growing in such a large container: too tall and too heavy. And way too awkward to wheel on its side into the truck to the greenhouse in the Fall, then back into the truck to the garden in the Spring. Sawing through the trunk turned a ten-foot tree into a five-footer that rode in the truck upright on the way back to the garden.


Would the tree resprout or die? To tell the truth, I might not have had the nerve to saw through the trunk if there weren't already these volunteer sprouts at its base.


Cussonia paniculata resprouts around base of trunk 061816 640


Chances are that, even if no new growth emerges higher up, these basal sprouts will become more active. Indeed, it's not too anthropomorphic to say that, with the top growth sawn off, the lower growth was set free.


Higher growth is often able to suppress further development of lower growth. This makes sense: Up there, the sun is likely to be stronger and the shade less, so the plant is better served by developing even more growth at those optimal elevations.


I'm betting that if this particular Cussonia paniculata were growing in its native southern Africa, these lower sprouts might never have emerged. In conditions so suitable to its needs, the tree bears foliage year-round and is always more or less active. The top growth stays in control.


Indeed, I wasn't able to locate pictures of the trees growing outdoors where they are hardy that show basal sprouts. True, it could be because accessible leafy growth can be browsed: One common name for this tree is goat's food. But it could also be that upper growth suppresses lower growth year-round.


Cussonia wouldn't survive outdoors in Rhode Island even to Thanksgiving, let alone through the Winter. So I must overwinter the tree in a greenhouse that, for economy, I don't heat to warmer than fifty degree Fahrenheit. Worse, for month after month there are the Winter's weak sun and short days.


This subtropical tree toughs it out by going dormant, i.e., shedding its glorious blue leaves. From mid-October until new leaves emerge any time from December through February, then, the inhibiting power of active higher growth is gone. The rest of the tree is, so to speak, unsupervised and free to rebel.


Sure, conditions are bleak, but isn't some freedom better than none? Apparently so, because a couple of years ago, these basal sprouts emerged. But just as they might have started into enthusiastic growth in late Winter, the new crop of top foliage appeared. The higher-growth-inhibits-lower-growth boom was lowered once again, and the basal sprouts were held inactive for the entire growing season.


But this Spring, I had sawn off all of that mean and controlling top growth. I slew it! Would the basal sprouts start into action? Then, my cabbage tree would grow as a cabbage bush. Fine with me: I'd still have plenty of the foliage, and on a plant that was vastly more compact.


But after a month in the sun, the basal sprouts still hadn't taken the bait. And as shown in the picture below, which was taken the same day as the one above, new top growth had begun emerging all around the stub of the sawn-off trunk.


Cussonia paniculata resprouts around the trunk top 061816 640


Five new shoots—and unlike the sprouts ringing the base of the trunk, each of these is thick and clearly up to something. Is there a connection between this active top growth and the still-inactive basal growth? Could be.


I'll update on this tree in September, when these new shoots will have reformed a top canopy of leaves. The cabbage tree will once again look like a tree.



Here's how to grow mountain cabbage tree.


Here's how exciting Spring's crop of new foliage is.

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