There is a great deal of variety within the Rudbeckia genus, and most of the 25 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). Black-eyed Susans make great cut flowers. The seed heads hold up well, too, and look attractive in arrangements.
Light
You will get the best flowering from your black-eyed Susans in full sun, but they can handle partial shade.
Soil
Black-eyed Susans are not particular about soil. They do best in soil that is not too rich and is well-drained, with a pH around 6.8.
Water
Keep the plants well-watered their first season to get them established—an inch per week through rainfall or irrigation is sufficient. Once established, they will be drought-resistant.
Temperature and Humidity
As a tough summer performer, this plant likes warmer temperatures of 60 degrees Fahrenheit and more. It handles both drought and humidity well, but it does need good air circulation to avoid powdery mildew.
Fertilizer
Go easy on the fertilizer. Black-eyed Susans grow even in poor, infertile soil. A side dressing of compost should be all they will need.
Types of Black-Eyed Susan
There are several excellent varieties of black-eyed Susan, including:
Rudbeckia hirta ‘Becky’: a compact dwarf variety Rudbeckia hirta ‘Maya’: resembles a tall marigold Rudbeckia hirta ‘Cherry Brandy’ with red to maroon flowers around dark center cones. Rudbeckia hirta ‘Cherokee Sunset’: has double and semi-double flowers in shades of yellow, orange, red, bronze, and mahogany Rudbeckia hirta ‘Indian Summer’: displays large yellow flowers, and reaches 3- to 4-feet tall. Rudbeckia hirta ‘Toto Rustic’: features autumnal hues; there’s also golden ‘Toto’ and pale ‘Toto Lemon’; all grow to about 1-foot tall
Propagating
Rudbeckia hirta is a relatively short-lived perennial that might not get old enough to form large, dense clumps. But if it does, it can be divided for propagation in early spring, just as new growth appears, or autumn, when the plant has finished flowering: Since black-eyed Susans easily reseed themselves, you might automatically have new plants in your flower beds next year.
How to Grow Black-Eyed Susan From Seed
To get a head start on the growing season, start black-eyed Susans indoors from seed about 10 weeks before the last expected frost. Plant seeds 1/4 inch deep in trays or pots filled with a moistened seed starting mix. Perennial varieties will germinate best if the seed containers are kept in the refrigerator or a similarly cold place for four weeks after seeding. Afterward, soil temperature needs to be warm for germination, so place the seeded tray or pot on a heating mat or a warm space such as the top of the refrigerator or a table above a heat vent. Seeds should germinate within 7 to 21 days. Harden off the seedlings before planting them outside. Make sure all danger of frost has passed before planting outside. Black-eyed Susans can also be direct seeded in the garden once daytime temperatures remain around 70 degrees. Scatter seeds. cover lightly with soil, and water well. Keep soil moist. Thin seedlings to 6-12 inches apart for dwarf varieties, 18-30 inches apart for larger cultivars. If you do not wish to start your own seed, seedlings and plants can be purchased and transplanted.
Common Pests & Plant Diseases
Black-eyed Susan is rarely bothered by serious pests and diseases. Septoria or angular leaf spots are two fungal diseases that form black spots on the leaves and stems. Provide good air circulation by leaving ample space between plants, and avoid getting the leaves wet when watering as that can spread the fungi. Removing and throwing infected leaves in the trash instead of composting helps to contain the spread.
How to Get Black-Eyed Susans to Bloom
Failure to bloom can be caused by lack of sun. Black-eyes Susans need full sun to bloom. One way to remedy that is to move your plants to a different location with full sun exposure but if it is a tree or shrub that is casting shade on them, some pruning might be sufficient to let more sunlight through. Some perennial varieties may not bloom until the second year. The other reason why black-eyed Susans won’t bloom is too much nitrogen, which results in lush foliage but no flowers. If using a fertilizer at all (the plants often do very well without fertilization), pick one that is high in bloom-boosting phosphorus.
Common Problems with Black-Eyed Susan
Powdery mildew can affect the leaves in hot, humid conditions. Minimize this by planting in full sun, and thinning the plants to allow for good air circulation.
