Try This Rudbeckia!
In New England, late summer is the time for rudbeckia. The rudbeckia most people are familiar with are “Black-Eyed Susans” – either the annual wildflowers of this name (Rudbeckia hirta) or their cultivated perennial cousins. At this time of year, big clumps of black-eyed susans are blooming in gardens, and it is not unusual to see large drifts of them growing in fields and meadows. But I want to call your attention to a much less well known rudbeckia, the cultivar called ‘Herbstsonne’ or ’Autumn Sun’.
Herbstsonne is a stately, more elegant member of the rudbeckia family. It is a big plant, growing 6’-7’ tall, and with a 3’-4’ spread. Its flowers are lemon yellow, rather than the more familiar gold of black-eyed susans. And the centers of these flowers are a fresh green, rather than dark brown or black (although, as the cones develop, they become more brown). Even when the flowers are not in bloom, the big foliage of this plant, growing about 5’ tall, is an impressive presence in the garden, making this what garden designers call an “architectural plant.”
A gardener using a plant this big in the garden needs to think about issues of scale and appropriate companion plants. I would be wary about growing Herbstsonne in a small flower bed with much smaller plants; I think it would just look like a looming giant. On the other hand, driving around the back roads of Maine, I have seen some people growing this rudbeckia alone as a specimen plant, treating it as a shrub, which definitely works. In the right partly shady space, it might be nice to grow Herbstsonne with Dicentra spectabilis (bleeding hearts), another big shrub-like perennial, but one that blooms in spring and goes dormant by mid-summer. I have Herbstsonne growing at the back of my blue and yellow border, with tall trees behind it and a somewhat shorter (5’) Heliopsis (false sunflower) growing in front of it. Because this part of my garden backs up to dense woods, it needs big, bold plants to set off the garden from the trees. Herbstsonne shares this space with other big plants, including tall spires of delphinium, Phlox paniculata (when the woodchuck doesn’t eat them ; see “The Lost Garden Season”,” August 2009) and a 4’ clump of Amsonia tabernaemontana (blue star flower). My friend Joyce, who first introduced me to Herbstsonne and gave me a division of it from her garden, has a very large three-storey house and grows this plant at the back of the border, up against the side of the house, where big plants balance the scale of the house. At Perfect Perennials in York, Pennsylvania, Diane Kendig has Herbstsonne growing side-by-side with the daylily ‘Autumn Minaret.’ (See “Extending the Daylily Season,” August 2009). I can see the logic of growing these two plants with similar heights and similar bloom times together, but I feel as though the bold personality of Herbstsonne swamps the more delicate beauty of Autumn Minaret. In the new fence border, I am planning to use Herbstsonne and Autumn Minaret to anchor the two ends of the fence at the back of the border, echoing one another, but with about 10’ between them giving both plants a chance to shine. Blue morning glories growing on the fence behind and beside Herbstsonne should provide contrast and balance its height and spread.