Crop Rotation Group
Miscellaneous
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Soil
Fertile, well-drained soil enriched with compost, with a neutral to slightly acidic pH.
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Position
Full sun to partial afternoon shade.
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Frost tolerant
Cold tolerance varies with species. Rudbeckia hirta is not winter hardy and is grown as an annual except in mild winter climates. Many other rudbeckias are hardy perennials, tolerating winter cold to -30°F (-34°C).
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Feeding
In spring, topdress the area around perennial rudbeckias with a balanced organic fertilizer. Drench with a liquid organic fertilizer when plants begin to grow tall in early summer.
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Companions
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Spacing
Single Plants: 11" (30cm) each way (minimum)
Rows: 11" (30cm) with 11" (30cm) row gap (minimum)
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Sow and Plant
Start seeds of annual black-eyed Susans indoors in spring, and expect germination in 10 days. Grow seedlings under strong light, and set them out when they have five or more leaves. Perennial rudbeckias can be grown from seed, but the seeds require cold stratification, making them a good subject for winter sowing. Alternatively, start with a purchased plant in spring, or plant divisions taken from the outside of a friend’s clump. Most improved cultivars are vegetatively propagated. Set out plants after the soil begins to warm in spring. Planting can continue into summer if the plants are adequately watered. In mild winter climates, perennial black-eyed Susans also can be planted in the fall. Young plants need water when they are actively growing. A surface mulch suppresses weeds while making the plants look more attractive. Once established, rudbeckias are quite tolerant of heat and drought.
Our Garden Planning Tool can produce a personalized calendar of when to sow, plant and harvest for your area.
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Notes
Several improved cultivars of perennial black-eyed Susan are worth seeking out. Vigorous 'Goldsturm' blooms for weeks in late summer; dwarf 'Little Goldstar' covers itself with blossoms. Tall, stately Rudbeckia triolba makes a great perennial for the back of the border. All rudbeckias are native American plants. When choosing black-eyed Susans for wildflower meadows, consider species native to your area.
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Harvesting
Gather stems for use in cut arrangements as you need them. Removing old flowers can improve reblooming in many cultivars.
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Troubleshooting
Powdery mildew is common late in the season, but it does not seriously weaken plants. Overly wet conditions can lead to crown rot. In spring, four-lined plant bugs may make numerous round spots in leaves, but the damage is seldom severe. Young plants may be nibbled by rabbits.
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