Summertime can be hard on many kinds of plants in our yards and gardens. We struggle to keep alive many types that are native to more tame climates. Soaring temperatures, unrelenting sun and days without rain take their toll on plants of all kinds, even trees and shrubs that are native to our region.
So, it is good to take note of plants that year by year never fail to provide superior color during these hot summer days. Rudbeckias, or yellow coneflowers, are a group of native perennial flowers that never fail to set the garden ablaze with bright yellow color.
There are many popular types, and several are represented well in the IDEA Garden in the Tyler Rose Garden. One of the most popular varieties in the trade is Rudbeckia “Goldsturm,” which has won many awards, and was designated Perennial of the Year in 1999. Its uniform, compact growth (2 to 2 1/2 feet), and abundant yellow ray flowers with a dark brown eye makes a great “in-front-of-the-border” plant to combine with other taller plantings.
One of the nicest designs I’ve seen was a large drift of Goldsturm in full bloom set against a backdrop of taller Miscanthus ornamental grasses, creating a very informal but high-impact scene.
Goldsturm is a hybrid of Rudbeckia fulgida x sullivantii. I mention this because Goldstrum will produce seedlings, and although the seedlings do not come exactly true to the original, they nevertheless also make great garden plants, mainly lacking the uniformity of height of Goldsturm. All R. fulgida are long-lived perennials that spread by rhizomes, creating a slowly spreading colony of sunny summer flowers.
On the opposite end of compact is Rudbeckia nitida Herbstonne (also said to be a hybrid between R. nitida and R. laciniata). This tall bloomer makes sure its bright yellow flowers are seen, as it grows to at least 6 feet tall. Don’t fertilize this one or it will be flopping over by end of summer. This is an ideal plant for the back of a mixed border, or along a fence. A great companion plant for Herbstonne is Salvia Indigo Spires, which competes with it for size and flower power. The blue of Indigo Spires makes a great compliment to the bright yellow Herbstonne. Salvia Mystic Spires Blue is a shorter version of Indigo Spires. Another large companion might be one of the large-blooming mallow hibiscus, like Flare.
Giant coneflower (Rudbeckia maxima) is a common roadside perennial that habits moist ditches. Its large, blue foliage is attractive by itself, and then in late spring tall spires of yellow daisies shout for attention. A tough native that can be used in raingardens and in perennial beds where bold texture is needed.
Gloriosa Daisies or Black-Eyed Susans are the common name for Rubeckia hirta, another great coneflower in this group of summer bloomers. Gloriosa Daisies are often grown as annuals or short-lived perennials, because they bloom easily from seed, and have large, attractive blooms. A new variety called Denver Daisy was the hit of the Horticulture Field Day a few years ago at Texas A&M at Overton. Growers, landscapers and gardeners got to pick their favorites with red flags, and Denver Daisy was an overwhelming favorite. It was covered with large, bright yellow flowers and by the end of the day, also covered with red flags.
There are several R. hirta cultivars on the market, including All-America selections Indian Summer, Cherokee Sunset and Prairie Sun, with more introduced every year.
All Rudbeckias need full sun, well-drained soil and only moderate water. For bright summer color, try a yellow coneflower this year.
Keith Hansen is Smith County horticulturist with the Texas A&M AgriLife Extension Service. His web page is EastTexasGardening.tamu.edu. His blog is http://agrilife.org/etg .