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Hort in the Home Landscape

A blog devoted to sharing timely horticulture topics and answering the questions of gardeners and homeowners.
2014-08-06 00 09 48

POTW: Black Eyed Susan and Septoria Leaf Spot


Plant of the Week!

If there ever was a quint-essential perennial that instantly reminds me of summer, it's got to be the Black Eyed Susan (Rudbeckia fulgida). This dependable perennial is blooming beautifully right now.

More than likely if you've got black eyed susans in your landscape, it's the 'Goldsturm' cultivar. 'Goldsturm' grows about 2-3 feet tall with bright yellow flowers and is really the standard cultivar for this species. 'Viette's Little Suzy' is shorter at only 10-14 inches tall with yellow flowers.

Although this plant reminds me of summer, it also is a great plant for the fall landscape because the bloom time ranges from July to October. It is great planted with other Illinois native perennials like Purple Coneflower, or native grasses like Prairie Dropseed. Similar to many other natives, the black eyed susan also tends to seed itself in and slowly spread.

Black eyed susans can be easily grown in a well-drained soil and in a full sun location. For the most part, they are problem free, although there are a few leaf spot diseases that can cause some unsightly issues with the foliage. Mine in particular are looking especially spotted this summer, likely due to Septoria leaf spot, caused by the fungus Septoria rudbeckiae. Symptoms begin as small, dark brown lesions, which enlarge to one-eighth to one-fourth inch in diameter. Learn more here: http://hyg.ipm.illinois.edu/pastpest/200507c.html

While Septoria leaf spot is unsightly, the damage is primarily cosmetic, and infected plants will bloom. Infected leaves may die a little earlier in the fall than uninfected leaves. A general-purpose garden fungicide may help reduce the spread of the disease, but these chemicals are protectants and do not cure infected leaves. Another strategy is to simply plant a facer plant in front of the black eyed susan to cover the unsightly leaves.

The best way to avoid this disease is by proper spacing. We tend to plant black eyed susan in large masses, but if plants were more isolated to allow better air movement, some of these fungal problems may be avoided.

Learn more about black eyed susan here: http://urbanext.illinois.edu/hortanswers/plantdetail.cfm?PlantID=744&PlantTypeID=2



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