Common Comfrey
Symphytum officinale
Common Comfrey, also known as Knitbone, is a hardy perennial valued for its medicinal properties and ability to enrich soil. Originating from Europe, it is often grown for its lush foliage and vibrant flowers, making it a popular choice among gardeners.
Everything it needs
9 essentials at a glance
Watering
Common Comfrey prefers consistently moist soil, so water it thoroughly when the top inch of soil feels dry.
During the growing season, this may mean watering once a week, while in the winter, reduce frequency to every two weeks. Signs of over-watering include yellowing leaves and root rot, while under-watering may cause wilting and leaf drop.
Light
Common Comfrey thrives in full sun to partial shade, ideally receiving at least 6 hours of direct sunlight daily.
It can tolerate some shade, especially in hotter climates, but too much shade may hinder growth. Ideal placement is in a garden bed or area that receives morning sun and afternoon shade.
Soil
This plant prefers well-draining, loamy soil with a pH range of 6.0 to 7.0.
It benefits from organic matter, so consider using a potting mix that includes compost or well-rotted manure to enhance drainage and nutrient content.
Humidity
Common Comfrey prefers moderate humidity levels, around 40-60%.
To increase humidity, mist the leaves or place a humidity tray nearby. Signs of humidity stress include browning leaf tips and edges, while too much humidity can lead to fungal issues.
Temperature
Ideal temperature range for Common Comfrey is between 60-75°F (15-24°C).
It is hardy in zones 3-9, tolerating cold down to -30°F (-34°C) and heat up to 90°F (32°C). During extreme temperatures, provide some shade or protection to ensure healthy growth.
Fertilizing
Use a balanced fertilizer with an NPK ratio of 10-10-10, applying it every 4-6 weeks during the growing season.
Reduce fertilization in the fall and winter. Signs of nutrient deficiency include yellowing leaves, stunted growth, and poor flowering.
Pruning
Prune Common Comfrey in early spring to remove dead or damaged leaves and to encourage bushier growth.
Use sharp, clean shears for cutting. Deadheading spent flowers can promote further blooming and prevent self-seeding.
Repotting
Repot Common Comfrey every 2-3 years or when it becomes root-bound.
Choose a pot that is 1-2 inches larger in diameter. Signs it needs repotting include roots growing out of the drainage holes and stunted growth. To repot, gently remove the plant from its pot, loosen the roots, and place it in fresh soil.
Propagation
Common Comfrey can be propagated through root cuttings or division.
For root cuttings, take a 4-6 inch section of a healthy root in early spring, plant it 2 inches deep in moist soil, and keep it shaded until new growth appears. Division can be done in spring or fall by separating established clumps and replanting them.
When it's unhappy
Yellow leaves
Why it happens
Often caused by over-watering or nutrient deficiency.
How to fix it
Check soil moisture and reduce watering frequency. If nutrient deficiency is suspected, apply a balanced fertilizer.
Root rot
Why it happens
Typically caused by overly wet soil conditions.
How to fix it
Ensure proper drainage and reduce watering frequency. Remove affected roots and repot in fresh soil.
Wilting leaves
Why it happens
Usually a sign of under-watering or extreme heat.
How to fix it
Water the plant thoroughly and provide shade during hot weather.
Fungal issues
Why it happens
Excess humidity and poor air circulation can lead to fungal infections.
How to fix it
Improve air circulation around the plant and reduce humidity levels. Treat with a fungicide if necessary.
Pests (aphids, slugs)
Why it happens
Common Comfrey can attract pests, especially in warm, humid conditions.
How to fix it
Inspect regularly and treat with insecticidal soap or neem oil for aphids, and hand-pick slugs.
Care through the year
Spring
In spring, prune back any dead foliage and prepare the soil for planting. Fertilize with a balanced fertilizer to support new growth.
Summer
During the summer, ensure consistent watering, especially in hot weather. Monitor for pests and apply treatments as necessary.
Fall
In fall, reduce watering as the plant enters dormancy. You may also want to cut back the foliage to encourage healthy growth in spring.
Winter
In winter, reduce watering frequency and protect the plant from extreme cold. If grown in pots, consider moving them indoors or to a sheltered area.
Toxicity & Safety
Common Comfrey is considered toxic to pets and humans if ingested in large quantities. The leaves and roots contain pyrrolizidine alkaloids, which can cause liver damage. Symptoms of ingestion include nausea, vomiting, and abdominal pain.
Good to know
How often should I water my Common Comfrey?
Water Common Comfrey thoroughly when the top inch of soil feels dry, typically once a week during the growing season and every two weeks in winter.
Why are my Common Comfrey leaves turning yellow?
Yellow leaves can indicate over-watering or a nutrient deficiency. Check the soil moisture and consider applying a balanced fertilizer if needed.
Can I grow Common Comfrey in a pot?
Yes, Common Comfrey can be grown in pots, but ensure the pot has good drainage and is large enough to accommodate its root system.
What is the best way to propagate Common Comfrey?
The best methods for propagating Common Comfrey are through root cuttings or division in early spring or fall.
Does Common Comfrey attract pests?
Yes, Common Comfrey can attract pests like aphids and slugs, particularly in warm, humid conditions. Regular inspection and treatment can help manage them.
Is Common Comfrey safe for pets?
Common Comfrey is considered toxic to pets if ingested in large amounts, so it's best to keep it out of reach of animals.
When should I prune my Common Comfrey?
Prune Common Comfrey in early spring to remove dead leaves and encourage new growth, and deadhead spent flowers to promote further blooming.
Grows well with
Track this plant in your garden.
Set care reminders, log growth, and join a community of plant lovers.