Yellow is emblematic of summer, and many of our native perennials represent the season well with golden blooms, including plants of the genera Silphium, Rudbeckia and Helianthus. The tall, tough beauties perform when many other garden favorites have had their day and are beginning to fade.
These golden genera can lead your garden from one season to another. Silphiums begin the bloom parade in June or July, Rudbeckias follow, and those in the Helianthus crowd extend the show well into October, or beyond. This length of bloom time is a boon for wildlife. Butterflies and bees are naturally attracted to the bright, yellow blossoms for nectar and pollen. Later, when the flowers go to seed, birds have time to feast.
Native to the eastern United States, Silphium attracted botanist William Bartram’s attention when he was exploring the Southeast in the 1770s. In the records of his travels, he noted: “The most conspicuous, both for beauty and novelty, is a tall species of Silphium.”
Despite the beauty and novelty noted by Bartram, Silphium has been overlooked as a garden specimen and may be hard to find, except in native plant nurseries. All members of the genus are tall, in the range of 7 to 10 feet, and display 2- to 3-inch wide, yellow, daisy-like flowers.
Being creatures of meadows and fields, they are tough and tolerant of a wide range of conditions. The foliage is quite variable within the genus and displays some fascinating forms. Silphium laciniatum (known as compass plant) has large, deeply incised leaves that line themselves up in a north-south direction to minimize exposure to the harsh midday sun.
Silphium perfoliatum is commonly called cup plant due to the configuration of its foliage. The leaves are opposite one another on the stem, and the larger mature leaves, which can be up to a foot long, are fused at their bases, forming a “cup” around the stem. Rainwater pools in these vessels, providing birds with a drink.
The Rudbeckia genus has several dozen species, including annuals, biennials and perennials, all of which originated in North America. The nursery industry has created many hybrids, and rudbeckias come in all shapes and sizes. Some of the most magnificent are two native perennial giants, R. laciniata (green-headed coneflower) and R. maxima (great coneflower).
R. laciniata bears attractively lobed foliage and reaches 6-10 feet tall. The plant develops a branching habit as it matures. From mid-summer into autumn, numerous yellow flowers appear, which are 2-3 inches across with gracefully reflexed petals surrounding a green central disk.
Rudbeckia maxima enjoys popularity with garden designers due to its attractive gray-green, oval foliage and its tall flower stalk that is topped with a 4-inch bloom consisting of yellow petals surrounding a brown cone.
Native perennial sunflowers in the Helianthus genus, all sporting bright yellow blooms, flower in late summer and fall. Helianthus angustifolius (swamp sunflower) is native to most of the Eastern United States, and as its common name implies, it prefers a moist, rich soil. Helianthus maximiliani (Maximilian sunflower) is perhaps the toughest of the perennial sunflowers, being drought tolerant and able to survive in a variety of soil conditions.
Plants representing the Silphium, Rudbeckia and Helianthus genera often are available at the Cherokee County Master Gardeners periodic plant sales. For information about upcoming sales, visit https://cherokeemastergardeners.com.
– Mary Tucker is a North Carolina native who has lived in Cherokee County for more than 25 years. She is a Lifetime Master Gardener whose special interest is gardening with native plants.