North American Fruit Explorers mailing list at ibiblio

[Diane Whitehead <voltaire@islandnet.com>]

There are 25 species of comfrey. Many are used as groundcovers 
because they spread.  Obviously it is one of these that people are 
warning against.

Symphytum officinale was grown as a herb.  I think it makes a clump.

S. asperum makes a big prickly-leaved clump and has blue flowers.

S. x uplandicum, Russian comfrey is a hybrid of these. (S. asperum x 
S. grandiflorum). It makes a huge clump and seems impossible to kill. 
I rip off every leaf and use them for compost, and still it thrives. 
The bees love the flowers. Information sources disagree about whether 
it is sterile or whether it has seeded itself in lots of British 
hedgerows. I haven't noticed any seedlings here in 35 years.

Some are sold by nurseries for decorative purposes:

S. ibericum 'All Gold' is described as a 'handsome woodlander' in New 
Zealand.  From the picture, it looked like a clump-former.

I saw one used as groundcover at Hidcote Garden in England. It had 
spread over such a large area that I decided never to plant it. (S. 
asperum x grandiflorum x officinale  'Hidcote Blue')

A couple more are listed by nurseries for groundcover: S. azureum and 
S. rubrum.

--
Diane Whitehead  Victoria, British Columbia, Canada
maritime zone 8
cool mediterranean climate (dry summer, rainy winter - 68 cm annually)
sandy soil