Northumberland,
United Kingdom 
Please could I get some advice on my Heuchera Key Lime Pie as it looks really horrid? Two photos attached. Could the red dots be rust or could spider mite cause this? We have lots of red spider mite but it's never affected any of my plants before. I am keeping plant in the shade as recommended and of course it's had plenty of water!! It's in a pot. I cut off all of the leaves in spring because they looked like this and the new growth was very healthy but then all of a sudden the blotches and spots came back :-( Also, is this problem likely to affect cutting of Heuchera Obsidian that I am currently nurturing or it it linked to Key Lime Pie only? Poor thing is starting to flower but the leaves look so horrid I'm thinking of cutting them all off again! Cross fingers you can help me to restore this lovely plant!
20 Jun, 2012
Answers
Thanks for the tip! Definitely need to create some space between my heucheras :-) Bit late to go out and chop the leaves now (although I was busy in the garden until 10:30 last week!)
20 Jun, 2012
The only treatment is to remove the affected leaves and burn them if possible...check all your heuchera's fairly often now. You simply have to keep on top of the problem I am afraid.
20 Jun, 2012
Ooh. Pleased I read this as some of my heuchera leaves look a bit like this.
21 Jun, 2012
I think that's rust on the back of the leaves about 50% of mine have it at the moment too. Someone will be along soon to recommend treatment (or google Heuchera rust)
Seems very common this year.
http://pippagreenwood.com/pippas-gardening-news/112/heuchera-rust-my-first-meeting
20 Jun, 2012