Ferguson: Sunflower, blackeyed Susan relatives provide yellow color in landscape

Published 11:47 am Friday, July 1, 2022

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Many people are familiar with common sunflower (Helianthus annuus) and blackeyed Susan (Rudbeckia hirta). There are, in fact, many relatives of these plants that look similar, and some are among the plants that are reliably perennial in Louisiana. In addition to providing a splash of yellow color in the landscape, they also attract bees and butterflies.

Being in the aster family, Helianthus and Rudbeckia species flowers are compound. The flower center is made up of multiple disc flowers, while what look like petals — what’s yellow in this discussion — are individual ray flowers.

Orange coneflower (Rudbeckia fulgida) is closely related to blackeyed Susan — it’s sometimes even called blackeyed Susan — but is more likely to survive from year to year. Proven varieties include Goldsturm and Early Bird Gold. The latter was discovered as a seedling of the former. Early Bird Gold begins blooming earlier and is more compact than its parent variety, with flower stalks reaching about two feet tall.

Orange coneflower should be planted in a well-drained bed in full to partial sun.

If you don’t mind a plant that grows quite tall and may fall over, great or giant coneflower (Rudbeckia maxima) has an impressive bloom. The flowers have prominent centers and occur on stalks that can reach six feet tall. Great coneflower has large leaves, reflected in one of its common names, cabbage-leaf coneflower.

Swamp or narrowleaf sunflower (Helianthus angustifolius) is similar to great coneflower in that it gets quite tall and is better suited to a naturalistic setting than a highly manicured landscape. Swamp sunflower has narrow, linear leaves though, and instead of blooming in the spring and summer like great coneflower does, it blooms in the late summer and fall. It tolerates wet conditions and is often seen in roadside ditches.

Although they’re grown as annuals rather than perennials, I’ll also mention Suncredible Yellow sunflower (Helianthus hybrid). It’s one of the 2021 Louisiana Super Plant selections. This is a branching sunflower that blooms continuously until we get a hard frost. It grows to approximately three feet tall.

Let me know if you have questions.

Dr. Mary Helen Ferguson is an Associate Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu, 985-839-7855 (Franklinton) or 985-277-1850 (Hammond).