With their bright yellow petals and dark center disks, black-eyed Susans have become a garden staple. There is a great deal of variety within the Rudbeckia genus, and most species are true workhorses with very few problems. Fast-growing black-eyed Susan is easily the most commonly known Rudbeckia, with its daisy-like flowers with large seed heads. It also has the scratchy, hairy leaves that are characteristic of its genus (this may not be one of its best features, but it does help keep pests away).
This wildflower is native to the central United States and can be seen growing in natural areas and along roadsides in the Midwest. Its ability to self-seed makes it a great choice for abundant wildflower gardens. You can plant it after the last frost in spring. It will flower in its first summer, but it can take two to three years to reach full height.
The size of Rudbeckia plants varies greatly, from dwarf (1 foot tall) varieties like ‘Becky’ and ‘Toto’ to the giant Rudbeckia maxima, which can reach 9 feet tall. Growing conditions and weather also affect the mature size of plants.
Black-eyed Susans are easy to establish, and they naturalize well and require little maintenance other than deadheading. Regular deadheading of the faded flowers keeps the plants in bloom longer. You can let the last flowers of the season remain on the plants to go to seed to feed the birds, but you will also get a good deal of self-seeding, which might not be a bad thing.
Rudbeckias are clump-forming, but plant division is necessary only if the clump gets too large for its space, or if you want to make more plants. The clumps typically do not die out in the center, so they don’t require frequent division.
Black-eyed Susans and other Rudbeckia plants work equally well as a complement to blue and purple flowers, like Russian sage and Veronica, or mixed in with other jewel tones, such as sedum ‘Autumn Joy’, purple coneflower and New England asters. Black-eyed Susans make great cut flowers. The seed heads hold up well and look attractive in arrangements.
You will get the best flowering from your black-eyed Susans in full sun, but they can handle partial shade.
Black-eyed Susans are not particular about soil but will do best in soil that is not too rich and is well-drained.
Keep the plants well-watered their first season, to get them established. Once established, they will be quite drought-resistant.
Temperature and Humidity
This plant likes warmer temperatures of 60 degrees Fahrenheit and more. It handles both drought and humidity well.
Go easy on the fertilizer. Too much will result in weak stems and plants. A side dressing of compost should be all they will need.
Are Black-Eyed Susans Toxic?
Black-eyed Susans are not toxic to humans or pets, they are mildly toxic to livestock (like swine or cattle).
After the flowering season, cut back your black-eyed Susans to 2 inches from the ground. Once the first frost happens, they can be leveled to the ground.
After you’ve trimmed the stems down, cover your black-eyed Susans with a healthy cover of mulch.
Common Pests & Diseases
Black-eyed Susans are deer-resistant once their leaves become coarse and hairy, but tender young growth may get nibbled.
Powdery mildew will affect the leaves in hot, humid conditions. Minimize this by planting in full sun, and thinning the plants to allow for good air circulation.
Information courtesy of TheSpruce.com