A Gardening Journal

Good Together: Short-toothed Mountain Mint with Purple-leaved Ninebark

Mountain mint is a garden essential because its flowers are beloved by insect pollinators, and they emerge for weeks and weeks from Summer to early Fall.

 

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But the flowers themselves play almost no part in creating the plants' intense visual appeal. Instead, the show depends, first, on the pair of silvery leaves that flanks each flower cluster—and, then, on the colorful sepals that protect the flowerbuds and endure long after the flowers have fallen.

 

In the picture below, you can see just how marginal the flower's aesthetics are. Tiny, white with lavender spots, and appearing only a few at a time, mountain mint blossoms are peripheral, literally, to the real action: the tight cluster of buds. Pale green sepals enclose each bud. The central buds are the last to mature, and retain tiny patches of burgundy. 

 

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The pair of leaves immediately below the flower cluster are known as bracts. They are covered in white fuzz and, as in the picture below, reflect so much sun that they seem to be silvery white. (Lower leaves are plain green.) They create mountain mint's large-scale appeal: A colony can be seen from across a field, or from the other end of the block. The bright, numerous bracts also create the initial excitement when mountain mint is planted near something with darker leaves. In my garden, that's purple-leaved ninebark. 

  

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Its foliage emerges dark burgundy in Spring, and stays that dark all Summer. This timing is particularly important in planning a powerful display with mountain mint. The silvery bracts of Pycnanthemum muticum don't emerge until Summer, and are showy right until hard frosts. The dark foliage of Physocarpus opulifolius 'Summer Wine' doesn't just not fade as Summer wears on and Fall approaches: it intensifies. The picture below was taken late in October. The Physocarpus foliage is as dark as ever. As Fall develops in November, it will become even more colorful: Lower leaves will turn cherry red even as the youngest leaves maintain the dark burgundy.

 

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Throughout, the interplay of colors between Pycnanthemum and Physocarpus just intensifies, too. The broad-brush contrast of the former's silvery bracts with the latter's burgundy leaves is just the obvious one. By November, the mountain mint's sepals have matured to a tan that not only contrasts with the silvery bracts, but also harmonizes with the burgundy and cherry red of the ninebark's stems and leaves.   

 

But from the moment the Pycnanthemum flower clusters appear near the Physocarpus foliage, the burgundy patches of the youngest sepals establishes a link between the two plants that is ideal in its inclusiveness and power: Those sepals are the smallest readily-visible detail of the mountain mint, much more so than the lavender dots on the flower petals. The sepals harmonize with the largest detail of the ninebark—its dark foliage. By contrast, the juxtaposition of fuzzy silvery bract to smooth burgundy leaf, no matter how vibrant it may be, is superficial.

 

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Here's how to grow a cousin of short-toothed mountain mint. Virginia mountain mint, Pycnanthemum virginianum, also has a pair of bracts that flank each of its flower clusters, but they are smaller in size and more subtle in appearance. In Winter, the bracts fall away but the flowerheads remain, bringing a subtle elegance to the garden and to dried arrangements. The hardiness, appeal to pollinators, cultural needs, and handling of Pycnanthemum virginianum are similar to those of P. muticum.

 

Here's how to grow purple-leaved ninebark, Physocarpus opulifolius 'Summer Wine', as well as a look at how interesting its stems are when leafless during the Winter.

 
 
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