The only book I know of on the subject is: Dierama; The Hairbells of Africa by OM Hilliard and BL Burtt. It's not readily available. If you find someone willing to swap, grab it!

Here is a link that might be useful: Rainbow Gardens Bookshop

Try this website:

http://www.bookfinder.com/search/?author=&title=dierama&submit=Begin+Search&new_used=*?cy=USD&mode=basic&st=sr&ac=qr

Hope it will help!

Edna,

I purchassed "The Harebells of South Africa" in RHS Wisley bookshop two years ago. You can contact them through the RHS website and enquire if it is still available.

paddy