A Gardening Journal
The Best Season Ever: Paddle Plant
- Published: October 02 2016
A kalanchoe or two—or three or four or five—should find its way into your collection. One, velvet leaf, will slowly grow to twenty feet, but most of the others stay compact enough to grow on a warm windowsill all Winter, and a sunny spot in the garden all Summer. Paddle plant is the second in my collection.
Pairs of blue leaves the size and thickness of pancakes ascend thick stems; if the plant never did anything else, its talent as living sculpture would still be unsurpassable. At first, I set my large pot of Kalanchoe luciae alone at the front of the terrace, satisfied that it was creating interactions not just with nearby plants but with nearby terra cotta. The width and unusual shallowness of its pot (plus the improvised base of three inverted smaller ones) was a pleasing accent not only for the huge terra cotta bell pot at their back, but also the pot-topped columns of terra cotta flue tiles. One is in the distance, displaying a potted Mexican grass tree; the other is in the center of the shot, almost hidden by its cascade of runners of variegated St. Augustine grass.
But then the striking texture, coloring, and scale of paddle plant's foliage and stems transfixed me. The icy white stems seemed arctic in their coolness; the pale blue leaves are darker only in comparison, and make the stems appear to be lighted from within. Like a siren song, these details compelled me to get closer and closer, bringing complementary plants time and again to set near the kalanchoe.
The leaves' smooth shapes, large size, and orderly array juxtaposed shockingly well with the tiny blue-green foliage and scraggly branches of a rosemary. They changed that bush's gestalt from tired and scrawny to high-fashion skin and bones.
At the lower left, tiny fat leaves of variegated elephant food provided effervescence that contrasted as well with the comparatively enormous paddles of the kalanchoe as the darker conifer-like needles of the rosemary.
But the foliage and stems of Kalanchoe luciae are so striking they can perform a full concert as a soloist. Their simplicity admits only a few details, but each is exquisite.
What about the leaves' plummy edge? More than an elegant touch, the rosy edges are a kind of colorful thermometer: As temperatures become cooler, the edge becomes thicker and thicker. In the frost-free chill of Winter in, say, Los Angeles, almost the entire surface of the leaf blades turns orange-pink-rose. In any climate, you can help the coloring expand as well as deepen by withholding water so that the plant husbands its succulent leaves' and stems' reservoir of moisture all the more: drought stress synergizes colorfully with temperature stress.
Early Fall in southern New England is likely to be too chilly, not too warm, but temperatures that are too hot or sun that is too strong also cause the foliage edges to redden. My pot received ambient water but the Summer was so dry I supplied some extra: my priority was overall growth and fullness, and the mild stress that helps maximize the foliage color could have brought that activity to a halt. No drought stress here—which could be why the reddish rims are still so slender during these still-mild days before the plant is sheltered in the greenhouse.
For the blue-green color to extend out to the rims of the leaves—indicating that the plant was experiencing ideal conditions for growth—circumstances would have to be just right: neither too dark nor too bright, too cold nor too warm, too wet nor too dry. Looking down into the heart of the plant at the stem's tip, you can see foliage that is enjoying such Goldilocks conditions: the young leaves.
The mature leaves protect the young ones from sun that is too strong. It's thought to be an advantage that all the leaves, mature and juvenile, are more or less vertical. This minimizes exposure to the hottest sun from directly overhead even as it ensures exposure to the more comfortably intense lower light of morning and afternoon. The tight nesting of the young leaves within layers of mature ones probably also protects them from quick changes in temperature, both from wind and from the daily changes from chilly to hot to chilly, night to day to night, typical of the near-deserts of this species' native Madagascar. In short, the young leaves are swaddled in a veritable nursery of gentleness. No wonder their surface—their skin—is like that of a baby: unblemished and free from sunburn.
In the close-up below, you can just detect individual silvery hairs that provide still more sun protection as they create the pale surface that pleases their human viewers. The hairs also cause water drops to bead up like jewels.
Each detail of this plant's foliage and stems really does contribute to its plant-as-art presentation! But artful beauty isn't relevant to the plant's success either in the garden or the wild. Water that beads up doesn't soak into the leaves and, so, doesn't cause the rot that such thick succulent foliage could incur.
Below, you can see other details that are at once sculptural (hooray human viewers!) and facilitative (hooray species longevity!). Although the bases of each pair of thick leaves attach directly to the stem—they don't have a more typical leaf stem, known as a petiole—they still leave a gap at either side. Note, also, that the center of each area of attachment is higher up the plant's stem than the sides. Water can slip down through the nest of juvenile foliage to this more open area. As a given drop accumulates to a critical mass, it slides to one side of the leaf base or the other, then slips into the gap between that leaf base and that of its partner on the other side of the stem.
Now look again at a section of mature stem. Each pair of leaves is oriented at ninety degrees to the pairs above and below it. Water that strikes the inner surfaces of each leaf is shunted downward towards its stem. That little stream of water is divided in two at the base of the leaf, which slows the speed of descent just a bit. The divided stream is then shunted onto the centers of the bases of the pair of next-lower leaves, where it is again divided in two, slowed down just that little bit, then shunted farther down. In effect, the entire stem is acting like a Japanese water chain, collecting rainwater that falls on all of its leaves and directing as much of it as possible smoothly down the stem to the ground.
In its preferred conditions—rocky spots at tops of hills in dry climates with harsh sun and plenty of wind—rainwater is scarce and drains away quickly. Kalanchoe luciae benefits by grabbing all the rain it can and shunting it directly down its stems to the plant's roots, where there's the best but still brief chance of absorbing some of the water before it flows out of reach.
This strategy also suggests the appropriate soil when growing paddle plant in containers or, in climates that are frost-free or nearly so, directly in the garden: gravelly with plenty of sand but little organic matter.
Here's how to grow velvet leaf, Kalanchoe beharensis. Its hardiness and handling are similar.
Here's a look at the new foliage of velvet leaf. In contrast to that of paddle plant, it is fully exposed the moment it emerges. This could be one reason it is completely swaddled in white fuzz so dense and thick it could function as a baby blanket, protecting the tiny new leaves from strong sun, hungry predators, and unwanted cold.