The peculiar flowers of the firewheel tree (Stenocarpus sinuatus) appear as 1 to 1 1/2-inch spokes arranged in wheel-shaped clusters about 3 inches in diameter. They are likely to have you humming, “Turn, turn, turn” to yourself as you view their unusual structure.
Those blooms emerge a greenish white, but gradually deepen in color to coral, pale orange and—ultimately—red-orange. Usually most abundant in early autumn here in the U. S., they actually can show up at any time of year on old wood, sometimes directly on the trunk in a botanical trait called cauliflory. (That means “stem flower” and has nothing to do with cauliflower!)
Also known as yiel-yiel, tulip tree, and white silky oak, this stenocarpus is native to the rainforests of eastern Australia and Papua New Guinea. Only hardy in zones 9b through 11, it often is grown as a houseplant for its showy foliage, the new leaves tinged maroon when they emerge—turning to glossy dark green on top, matte pale green beneath. Eventually reaching up to 18 inches long, those leaves typically are lobed when the tree is young, smoother-edged but somewhat wavy when it matures—hence, the sinuatus species name.
Slow-growing at its start, the firewheel may not begin flowering until it is seven to ten years old or so. Related to the protea, it shares that plant’s aversion to phosphorous, so be careful that you don’t give it fertilizer with a high middle number. It should prosper in acidic, well-drained soil in either full sun or partial shade with average amounts of water. Although the tree can reach 100 feet in the rainforests, it isn’t likely to surpass 30 in your backyard.
If you want to try growing it from its winged seeds, add a little sand to your seed-starting mix and soak the seeds in warm water overnight before sowing them. Then, barely cover them with the mix and keep them in a location with temperatures in the 70s Fahrenheit until they sprout.
You will need to be patient—making sure to keep the mix damp in the meantime—as the seeds often take four to six weeks to germinate. Since their wings are just intended to help them fly farther from the parent tree, you generally can trim those off to make the seeds easier to sow if you wish.
The young plants should be kept in bright, indirect light rather than direct sunlight and exposed to the latter only gradually when they are older. Rain forest species, after all, usually don’t receive much sun until they push their heads up into the canopy.
In case you are wondering where the steno comes in, it translates to “narrow” and carpus to “fruit”—in reference to the tree’s bean-like seedpods. Why anyone would want to name a genus with flowers this extraordinary for its seed pods is baffling, but we always can revert to the more poetical firewheel. One of the few trees that bloom in autumn, it might even make you glad that the seasons are turn, turn, turning.
Photos: The banner photo is by palmbob and the other photo by Kell, both from the Dave's Garden PlantFiles. The antique image is by M. E. Eaton from Addisonia, Volume 8, courtesy of plantillustrations.org.