Blackeyed Susan
Rudbeckia hirtaUSDA | Grow Zone
3-10Outdoors all year in zones 3 to 10. Anywhere colder, keep it as a houseplant. Protect it below 0°F.
- Light
- Full sun, 6-8 hours
- Water
- Moist soil, weekly
- Humidity
- Moderate, adaptable
- Temperature
- 70-85°F (21-29°C)
- Difficulty
- Beginner
- Growth
- Moderate
- Mature size
- 2-3 ft tall, 1-2 ft wide
Rudbeckia hirta, commonly known as Blackeyed Susan, is a vibrant perennial native to North America. Renowned for its bright yellow flowers and dark centers, this plant attracts pollinators and adds cheerful color to gardens. Its hardiness and adaptability make it a favorite among gardeners.
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Ideal temperature
70-85°F is where it grows fastest. Below 0°F cold damage starts.
Spacing and harvest
- Mature size
- 2-3 ft tall, 1-2 ft wide
- Plant apart
- 12-24 in
- Frost
- Hardy: survives frost
Everything it needs
9 essentials at a glance
Watering
Rudbeckia hirta prefers consistently moist soil, especially during its growing season.
Water deeply once a week, allowing the top inch of soil to dry out between waterings. In hotter months, you may need to increase frequency to twice a week. Signs of over-watering include yellowing leaves and root rot, while under-watering may cause wilting and browning leaf edges.
Light
This plant thrives in full sun, requiring at least 6-8 hours of direct sunlight daily.
Ideal placements include south or west-facing gardens. While it can tolerate partial shade, too little light can result in leggy growth and fewer blooms.
Soil
Rudbeckia hirta prefers well-draining soil with a pH range of 6.0 to 7.0.
A mix of loamy soil with organic matter, such as compost, is ideal. Ensure good drainage to prevent root rot, as this plant does not tolerate soggy conditions.
Humidity
This plant enjoys moderate humidity levels but is quite adaptable.
To increase humidity, consider misting the leaves or placing a humidifier nearby. Signs of humidity stress include browning leaf tips and wilting.
Temperature
Rudbeckia hirta thrives in temperatures between 70-85°F (21-29°C) and is hardy in zones 3-10.
It can tolerate brief periods of heat but may struggle in extreme cold, so provide mulch in winter to protect the roots.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10, applying it every 4-6 weeks during the growing season.
Reduce feeding in late summer and fall. Signs of nutrient deficiency include stunted growth and pale leaves.
Pruning
Prune back spent flowers to encourage new blooms and maintain shape.
Use clean, sharp pruning shears and remove dead or damaged leaves as needed. Deadheading should be done regularly throughout the blooming season.
Repotting
Repotting is typically not necessary for Rudbeckia hirta as it is often grown as an annual or biennial.
However, if grown in pots, consider repotting every 1-2 years or when roots become crowded. Choose a pot 1-2 inches larger in diameter than the current one.
Propagation
Propagation can be achieved through seeds or division.
For seeds, sow them in spring after the last frost, covering lightly with soil. For division, dig up established plants in early spring or fall, ensuring each division has roots and foliage. Replant immediately.
When it's unhappy
Yellow leaves
Why it happens
Over-watering or nutrient deficiency.
How to fix it
Check soil moisture levels and adjust watering accordingly. Fertilize if nutrient deficiency is suspected.
Root rot
Why it happens
Poor drainage or over-watering.
How to fix it
Ensure proper drainage and reduce watering frequency. Remove affected plants and amend soil if necessary.
Leggy growth
Why it happens
Insufficient sunlight.
How to fix it
Move the plant to a sunnier location to promote bushier growth.
Powdery mildew
Why it happens
High humidity and poor air circulation.
How to fix it
Increase air circulation around the plant and apply a fungicide if necessary.
Pest infestations (aphids, spider mites)
Why it happens
Weak plants or environmental stress.
How to fix it
Regularly inspect plants and treat infestations with insecticidal soap or neem oil.
Care through the year
Spring
In spring, prepare the soil by adding compost and ensure proper drainage. Start watering regularly as the plant begins to grow.
Summer
During summer, maintain consistent moisture and deadhead spent flowers to encourage continuous blooming. Monitor for pests and diseases.
Fall
In fall, reduce watering as the plant begins to go dormant. Cut back spent foliage and mulch around the base to protect roots during winter.
Winter
In winter, if grown in pots, move them to a sheltered location to protect from frost. For garden plants, apply a layer of mulch to insulate the roots.
Toxicity & Safety
Rudbeckia hirta is non-toxic to pets and children. It is safe to grow around cats and dogs, with no known adverse effects from ingestion.
Good to know
Why are my Blackeyed Susan leaves turning yellow?
Yellow leaves on Rudbeckia hirta can indicate over-watering or a nutrient deficiency. Check the soil moisture and consider fertilizing if needed.
How often should I water my Blackeyed Susan?
Water your Rudbeckia hirta deeply once a week, increasing to twice a week during hot weather. Ensure the top inch of soil dries out between waterings.
What is the best soil for Blackeyed Susan?
Rudbeckia hirta thrives in well-draining soil with a pH of 6.0 to 7.0. A loamy mix with organic matter is ideal for healthy growth.
When should I prune my Blackeyed Susan?
Prune Rudbeckia hirta after flowering to encourage new blooms and maintain shape. Regular deadheading throughout the blooming season is also beneficial.
How do I propagate Blackeyed Susan?
You can propagate Rudbeckia hirta through seeds or division. Sow seeds in spring or divide established plants in early spring or fall.
What pests affect Blackeyed Susan?
Common pests include aphids and spider mites. Regular inspections and treatments with insecticidal soap can help manage these infestations.
How do I prevent powdery mildew on my Blackeyed Susan?
To prevent powdery mildew, ensure good air circulation around your plants and avoid overhead watering. If it occurs, treat with a fungicide.
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