A Gardening Journal

Today in the Garden of a Lifetime: Copper-Colored Stems in Fall

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These thick stems of warm copper couldn't be more welcome as Fall deepens and darkens to Winter. Six feet tall and more, they were only inches tall in May. Perhaps a coppice of willow, Siberian dogwood, or boxelder? Nope. These are stems of a perennial whose shameless and glad-to-see-you blooms are among the largest of any plant hardy north of Miami. When in flower in Summer, swamp mallow is automatically one of the garden's peaks. Leafless and flower-free after several hard frosts, it is still a peak. How many other perennials can say the same?

 

I grow this particular swamp mallow, Hibiscus coccineus, in a pot because it just misses being solidy hardy for me. Actually, I grow it in two pots, one for the white-flowered form, 'Moon Moth', and another for the straight species, whose flowers are cherry red. In a climate only degrees warmer, they could be planted directly in the garden; it is striking to see colonies thriving just a five-minute drive closer to the shores of Block Island Sound, whose waters are moderated by the Gulf Stream.

 

On the other hand, if my colonies were growing right in the garden, I couldn't have sited them so advantageously near the narrow 'Graham Blandy' boxwood at the left of the picture below, let alone directly in front of the glossy foliage of the Southern magnolias espaliered up the house: The mallows always grow a foot or two taller than usual because they sit in tubs of water; neither the box nor the magnolia would be happy growing pond-side. Just before bringing the pots into shelter, then, I can maximize the cool-weather display of the mallows' coppery stems by setting their pots near these evergreens.   

 

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These stems aren't copper in Summer. As with the color transition of so much foliage in Fall, these stems' warm-weather pigment—green chlorophyll—breaks down as weather cools, leaving whichever pigments are more persistent during the fluctuating and increasingly low temperatures. For Hibiscus coccineus, those cool-temperature-tolerant pigments are coppery.

 

But there's "cool" and there's "frozen." A drastic cold snap caused me to whisk the pots into the shelter of the basement moments after these pictures were taken. Perhaps next year, I'll mulch-in the containers to protect the underground portions of the colonies from sudden or increasing cold. Then, the pots could remain outside through Christmas, and the stems could transition from this copper color to what is probably a driftwood grey.

 

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Before Winter's worst arrived in January, I'd move the pots into the frost-free shelter of the basement. First, I'd cut the stems off at ground level; they become increasingly brittle in sustained cold and, by then, would tolerate little movement without snapping. Completely durable as long as they aren't jostled, they would provide handsome height for a dried arrangement for the rest of Winter: That's the third peak season in a row for this perennial. What other perennials can match it?

 

 

Here's a look at the purest-white flowers borne by Hibiscus coccineus 'Moon Moth' in Summer. Its flowers go with everything, and its stems are light green in fall, with none of the coppery tint of the straight species.

 

Here's how to grow 'Red Flyer', a hybrid of Hibiscus coccineus with H. grandiflora. The hardiness and handling of H. coccineus are similar.

 
 
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