Inside The New York Botanical Garden

Piet’s Pollinator Powerhouse

Posted in Gardening Tips on July 23 2014, by Sonia Uyterhoeven

Sonia Uyterhoeven is NYBG’s Gardener for Public Education.

trifolium rubens Franz Xaver
Red feather clover (Trifolium rubens)
Photo by Franz Xaver

Over the years, I’ve often given tours of the High Line to NYBG Members as part of our Membership tour programs. In fact, I’ve already given several this year and have more planned for August and October. And as I lead the groups through this unique space, we discuss architecture, ecology, design, and garden-worthy plants. Perennials in particular are always a hot topic.

I often warn the participants against some of the more rambunctious perennials, as they tend to have a thuggish habit. Instead, I recommend many of the other outstanding selections that you can find in the planting scheme created by Piet Oudolf, the High Line’s designer. The perennials planted there are chosen for their durability. Growing in 18 inches of porous soil atop abandoned railroad tracks that stand 30 feet above the ground, these plants are regularly exposed to intense urban heat, sunlight, and heavy winds—they have to be tough.

Piet Oudolf’s naturalistic planting style fits in superbly with the unstructured urban environment. He designed the High Line with plant communities in mind, using primarily native, resilient, and ‘low-maintenance’ plants that provide great diversity, seasonal change, and height and color variation.

Three of the plants selected by Oudolf happen to be tough, underused perennials that will serve as pollinator magnets in your own garden. The color theme of the trio is purple or mauve to pink, and the botanical family is Fabaceae. Let’s just call this group “peas to please.”

The first one to come into flower is red feather clover (Trifolium rubens), which opens in May and flowers into June. It’s a showy and statuesque ornamental clover. When I point it out during tours and ask the participants to identify the plant, few can figure it out off the top of their heads; this ornamental clover is simply too glamorous.

The fat flowers on red feather clover start out as hairy silver buds that open up to a rosy magenta. The blooms are a magnet for bees, butterflies, and hummingbirds from late spring into early summer. The plant reaches 18 to 24 inches tall and forms an impressive clump of oblong, globe-shaped flowers on upright stems.

Following hard on red feather clover’s heels is the diminutive but equally delightful purple prairie clover (Dalea purpurea). Purple prairie clover has fine, feathery foliage and a nice vase-shaped habit. It grows 1-3 feet tall, but I generally see it reaching just over 2 feet in this area.

Purple Prairie Clover daea pupurea Blaine Hansel
Purple Prairie Clover (Dalea pupurea)
Photo by Blaine Hansel

Purple prairie clover flowers from mid June until August. The last time I was at the High Line, the plant was smothered in several different species of bees. Honeybees, bumblebees, Miner bees, and a whole slew of other species can’t help but love these flowers. But who couldn’t? They present as oblong, green-and-silver cones atop wiry stems. A cylindrical mass of purple wraps around the bottom of the cone and slowly moves its way to the top. When the tiny purple flowers and their bright yellow anthers reach the middle of the cone, it reminds me of Bozo the Clown’s bald head protruding above a wide band of hair. These whimsical flowers are a lovely addition to any environmentally savvy border.

The final flower in this trio is the lead plant (Amorpha canescens). It grows up to 3 feet high in a semi-erect fashion, although it starts into an elegant sprawl as it grows larger. The lead plant hasn’t made up its mind as to whether it’s a perennial or a deciduous shrub, however—the light green stems are hairy when young and become woody as they age.

leadplant Amorpha canescens
Lead plant (Amorpha canescens)
Photo by Blaine Hansel

The compound leaves on this perennial are bipinnate and have a soft, orderly, fern-like appeal. The lead plant has 2- to 6-inch flower spikes that cluster at the end of their stems. The purple blooms support striking orange-yellow anthers. Bees love these blossoms, and not just bumblebees but green metallic bees and many others. Lead plants flower for several weeks in mid summer.

Studies have shown that native plants are more likely to attract native pollinators and provide them with the food they need. Providing a continuous food supply through succession of bloom is equally important. In the trio of plants we have looked at today, the inflorescences all have small, open flowers that cluster together on a stalk. They offer small snacks for pollinators and the nectar is easy to reach.

As members of the pea family, these clovers are all nitrogen fixers and perform spectacularly in lean soil, although they can handle a wide range of soil. The latter two are prairie plants and their deep root system allows them to recover from fires. Unfortunately for many gardeners, they are also high in protein, and deer and other herbivores find them delicious. Nonetheless, they are definitely worth a try if you have space in your garden.

Photos courtesy of Wikimedia Commons