The very first time I recall hearing the name Koelreuteria was at Sissinghurst, where there was a comically lame specimen in the cottage garden. No one seeing it would ever be tempted to grow one. Memory may be adding layers of lameness, but my recollection is of a single, leaning Dr. Suessian stem to about six metres tall, terminated by an ailing tuft of foliage.
But my next encounter was at the extreme opposite end of the appeal-spectrum. This time, in a garden in Castlemaine, Victoria, small trees of domed outline, as wide as they were high, carried some early autumn foliage peppered with paper-lantern seedheads. I was convinced I’d discovered by new go-to small tree for hot, dry environments.
Golden rain tree has a lot going for it. The deciduous pinnate foliage starts out slightly pink-tinged, quickly ripening to a fresh lime green, then deepening as the summer goes on. Some time about mid summer, each growth point is terminated by a great panicle of small yellow flowers. From a distance you could think you were looking at a wattle in bloom. The flowers last for weeks, and a proportion of them develop into inflated paper-bladder seed pods that are both triangular in shape and cross section. In my specimens, due either to genetics or climate, these are a bright lipstick pinky-red from the moment they start to develop, though on many trees I see elsewhere they remain green.
Their branching structure isn’t particularly predictable, which limits their use where uniformity is desired. But where it’s not (and I like my trees as distinct individuals), they’re appealingly idiosyncratic, and can be trained from early age as single-trunked specimens that branch at a certain point, or as multi-stemmed plants (a look which is finally taking off in response to this developing movement of naturalistic planting design, and is thankfully being celebrated by some growers).
Most of the specimens of golden rain tree that you see about the place are 4 – 6m tall, and depending on where they’re growing, can achieve about the same in width. There simply aren’t enough small trees that form umbrageous canopies, so this is a big plus, in my opinion. I find them reasonably fast growing, though a quick google reveals the Blerick tree farm describing it as a ‘fast growing, deciduous tree’ and Speciality trees stating that it is ‘an elegant, slow-growing small tree’.
Of course, with all those pros, there must be a few cons. The golden rain tree loses points, in my view, by hanging onto its lantern seed heads after shedding its foliage, by then usually brown, such that you’re occasionally tempted to try and deadhead them (though so far I’ve never acted on the temptation). Also, my plants (which may not be broadly representative) respond to moderate drought by folding their leaflets down vertically, against all good design instincts that says that a pretty pinnate leaf should hold itself out flat for best aesthetic advantage.
But the biggest disadvantage is that in subtropical zones, or the warmest of warm temperate areas, the golden rain tree has proven itself to be, to a degree, invasive. But that doesn’t mean that those of us in the cooler states should do anything but welcome and celebrate its drought tolerance, and fabulously distinct seasonal offerings.
Does it self-sow for you, where you are? And does it reliably colour up in autumn? Do you get coloured seed pods or are they just plain green?