A Gardening Journal

Good Together: Caribbean Copper Bush & Naranjilla

Euphorbia cotinifolia Solanum quitoense 101917 overall east toward the house 640

 

Weeks into fall, and still no frost! As warm weather last and lasts, summer-peaking displays of tropicals and annuals grow long in the tooth. This month, before everything is put away for the winter, is the time to ponder what worked and what didn't. Which plants and combinations will be reprised whole-hog next season, and which will either be reimagined or abandoned.

 

Tall shrubs of Euphorbia cotonifolia fooled more than one garden visitor into asking why I was growing purple-leaved smokebushes—which are in the genus Cotinus—in pots. 

 

Euphorbia cotinifolia Solanum quitoense 101917 fuller 640

 

Indeed, this euphorbia's round burgundy leaves that glow blood-red when young are uncannily like those of true "smokers" such as Cotinus coggygria 'Velvet Cloak'. But Caribbean copper bush is an unrelated tropical shrub-to-tree. The sticky white sap exuded by even the smallest break in a stem—or just by pulling off a leaf—is the giveaway that it's a euphorbia, and also ensures that this species is, as is typical for euphorbs, absolutely unpalatable to browsers.   

 

Euphorbia cotinifolia Solanum quitoense 101917 entire south quadrant 640

 

Thank goodness: These five containers are outside the deer-fenced portion of the property, so all the plants had better be nibble-proof.  

 

The large leaves of naranjilla are equally forbidding to herbavores. The felty gray fuzziness is but the pleasant dissuader. Needle-sharp purple spikes project out from the leaf veins both top and bottom, and provide a painful reminder that browsing is a bad idea. (The stems of this tropical shrub are thickly spiked as well.) 

 

Euphorbia cotinifolia Solanum quitoense 101917 close up 640 

 

In the shot below, you can see that the uniformity of the leaf's gray fuzziness has been disrupted by a pair of round green patches. These are where I touched the leaf, whose thrilling gray is actually overnight condensation. Where my fingers momentarily pressed the fuzziness down to the leaf's surface, the water droplets became joined into a generic wet patch that didn't reflect sunlight nearly as well.

 

Euphorbia cotinifolia Solanum quitoense 101917 closer 640

 

Closer still, the leaf's countless silvery-dropped hairs form a carpet through which the raspberry-to-toffee-tipped spikes penetrate like billionaires' skyscrapers above a city of townhouses.

 

Euphorbia cotinifolia Solanum quitoense 101917 closer still 640

 

As its latin name suggests, Solanum quitoense is native to Ecuador. There it favors the cooler (but still frost-free) higher elevations, not the steamy heat of the lowlands. The plant enjoys regular watering, especially in containers. Perhaps the ability of its fuzzy leaves to precipitate moisture from cool humid air enhances the plant's overall hydration. Certainly, the overlapping, moisture-trapping foliage of this bushy plant would "harvest" more moisture from the air than if the plant were sparsely-branched or leaved.

 

Below, a picture from one of my favorite mail-order nurseries, of Solanum quitoense growing to monstrous proportions. Note the immense green leaves. The picture was likely taken at mid-day, when any dew collected by the foliar fuzziness would either have been evaporated in the heat or already absorbed by the leaves. Note, also, how leaves overlap those lower down. Moisture that happened to drip from one leaf is not likely to travel far: It will strike lower foliage, to become trapped anew by still more stiff fuzz.

 

Solanum quitoense Top Tropicals 640

 

In its unusual "self watering" foliage, naranjilla is similar to California's redwoods. They thrive only when and where they can grow tall enough to condense and then capture sufficient moisture from the cooler air high above ground. Another key to success with redwoods is never to plant them as soloists. While even a single tree can grow high enough that its foliage can precipiate moisture, much of it will run off the short slender needles and drip down to more-or-less dry and sunny ground. There it is just as likely to evaporate back into the air as soak in.

 

By planting redwood in groups, dripping precipitation is more likely to strike foliage of a near-neighbor redwood, while any that does reach the ground will more likely land in the grove's cool shade that, even more handily, is thickly carpeted with the conifer's fallen needles. This water will soak in instead of evaporating or running off. The moisture-gathering effect of a thick patch of naranjilla would be the same.

 

But enough with the raves and geek-outs. The picture below shows how the combination of copper bush and naranjilla sometimes didn't quite work. Look closely, and you can see that the copper bush—a conservatory specimen that would always have needed to have been brought back into shelter—wasn't planted directly with the solanums, which are grown just as annuals outside their native tropics. Instead, I sunk the black nursery pot containing the copper bush into just the top two inches of the soil of the bell pot. To hold the six-foot copper bush in place, I drove a tall stake down through the nursery pot's center hole all the way to the bottom of the bell pot. 

 

Euphorbia cotinifolia Solanum quitoense 101917 skimpier 640

 

Keeping each species in its own pot ensured that I could easily separate the euphorb from the solanums in the fall. It also gave all the soil in the bell pot to the solanums, while adding that much more instant height to the ensemble. But even though I planted three solanums per pot, I didn't water them faithfully enough to ensure growth that was large and luxuriant enough to hide each nursery pot. Look back at the photo from Top Tropicals: the leaves of that patch of naranjilla are dramatically larger than mine. There could be a small car hiding behind that clump, where my trios often couldn't even hide a flower pot.

 

Would planting four solanums per pot, not three, enable denser coverage? Perhaps—but at greater hassle and risk: adding one more large plant to a fixed volume of soil would require that watering be all the more frequent. Worse, naranjilla that is drought-stressed drops its lower leaves, which would expose the nursery pots all the more cruelly.

 

In 2018, then, I'll stick with this same combination of three naranjillas to one copper bush—but I'll be sure to water the naranjillas' pot regularly. The euphorbia is somewhat succulent, though, so it doesn't need such frequent watering. No problem: The pot for the copper bush is set above that for the solanum so, when watering the latter, I won't also be watering the former.

 

Now, what about the plants in the stock tank?

 

Arundo donax peppermint stick cannas purple leaved various 101917 overall

 

By May, the tank was already bountiful with three giant pots of Arundo donax 'Peppermint Stick' but, by early June, I still had homeless pots of cannas—Black Knight, Intrigue, Tropicana—that were happy to grow aquatically. They were crammed in as well, and look it. Next year, the cannas will go elsewhere.

 

 

Here's how grow Euphorbia cotinifolia

 

Here's how exciting Euphorbia cotinifolia is from the moment new foliage emerges in the spring.

 

Here's how to grow Solanum quitoense. By the way, naranjilla is Spanish for little orange; a true orange is a naranja. This solanum bears tart, juicy fruits the color and size of small oranges. Where hardy, it is most often grown as a fruiting crop, not an ornamental.

 

 
 
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