By Sjw
gloucestershire,
United Kingdom 
I took some cuttings of penstemon about 6 weeks ago and put them in water to root, there are no signs of any roots yet. Is it too late to take cuttings, I want to keep some in greenhouse over winter to ensure supply in case of a bad winter. What is best way.
10 Sep, 2015
No its not too late. I haven't tried rooting them in water. i put several round the sides of a pot and covered the pot with a plastic bag, taking care that it didn't touch any of the leaves. They need to be kept reasonably warm but out of direct sun or they may overheat under the plastic. I left the sides of the bag loose so that there was some air circulation. They took well like that. However they did take a year or two to get big enough to flower.
10 Sep, 2015