A Purple Autumn Perennial That Pops: Vernonia Lettermannii
January 4, 2015
Allan in Ironweed, Perennial Plants, Vernonia, autumn garden, perennials, purple flowers

Photo credit:The University of Tennessee, Institute of Agriculture

A client gave me a mandate to enhance her flowerbed whenever I find a reliable perennial that blooms in purple.

To please her, I scour my suppliers’ catalogues every spring looking for purple blooming plants. Then I test grow them for a few seasons to determine how they perform. Most are disappointing.  A few become messy or invasive. Some are short-lived plants lasting one or two seasons while others are unable to survive climate conditions in my growing zone.

Happily, this year I discovered that the recently introduced Vernonia lettermannii  - also referred to as Narrow-leaf Ironweed - meets my rigorous requirements for neatness and low maintenance. I intend to surprise my client by planting it in her garden this coming spring.  

Photo credit: Plantdelights.com

Although it is dramatically shorter than the species Vernonia arborescens or the variety Vernonia mammoth, lettermannii provides a far more intense color display than either of its taller cousins. It blooms in August and September in a bright true purple that projects from afar and happily holds its color in the August sun.

Unlike its taller relatives that fade as they age and shrink from view, the florets of lettermannii hold their form and maintain a vivid color [albeit slightly more reddish] long after dormancy sets in. By October, the flower heads may have long expired but their rich color, now on slightly scrunchy petals, sustains itself for another few weeks.

Here are several photos from this past season of Vernonia lettermannii  in one of my October flowerbeds:

Vernonia lettermannii satisfies gardeners’ needs on several fronts. It is a butterfly and hummingbird magnet. It feed a passion for purple flowers both when in bloom and into creeping dormancy and it enriches the color story of the autumn garden by extending the bloom season well into October.

photo credit: Plantdelights.com

An additional attribute is its magnificent feathery foliage. In late spring, the perennial shoots up to create a large, soft mound of glossy-green foliage that is enchanting to behold and heaven to touch. Throughout the growing season, this visual delight continues to add to the garden a] sumptuous architectural detail - think round but softer boxwood plants - and b] feathery sensuality like Amsonia hubrechtii.

Cold hardy in USDA Zones 4  [CND Zone 5] Vernonia lettermannii is a heat tolerant plant that grows two or three feet tall and wide in full sun, even in poor rocky soil, under average to dry conditions. Good drainage is required. Periods of inundation are tolerated, but not heavy or saturated soils.

Few if any retail nurseries stock Vernonia in any of its varieties. Consequently, all the varieties growing in my garden were purchased from mail order suppliers.

Here is how online seller Plant Delights.com  describes this flowering perennial :-

Vernonia lettermannii is a fascinating ironweed that hails from Arkansas and Oklahoma where it can be found in rocky soils and on rock outcrops. Imagine taking an Amsonia hubrichtii, shrinking it to 2' tall x 2' wide, shearing it into a round ball, then topping it with hundreds of purple flowers in August and early September, and you have Vernonia lettermannii...a hummingbird delight. We grow this in our hot, dry, scree garden where it has caused visitors to lust in their hearts.

The seller’s words above are not hyperbole. Although the variety lettermannii  is much shorter than the species, it  produces a far more dramatic color display than any of  its taller cousins and it holds that color long than they do - even after it goes dormant.

At that time of year, while the gardener is mournfully anticipating the falling leaves of autumn and when there is little or no color left in the fall flowerbed, Vernonia lettermannii can cheer the heart and  take one’s breath away.

Article originally appeared on Garden Design, Montreal, Perennial Flower Gardens, Gardening Tips, Gardening Advice, Gardening Book Reviews (http://allanbecker-gardenguru.squarespace.com/).
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