Northumberland,
United Kingdom 
I am trying to grow a 'hedge' in a row of plant troughs (about 6 inches deep)mounted on a low wall. The wall also supports a 3 foot fence which is supported by concreted-in posts.
I have tried pyracantha with 2 per trough but they have suffered badly in the winter. Is this because pyracantha needs deeper roots to escape the frost?
I did install a watering system for the summer and they did quite well in this season.
I am now looking for an alternative plant to use. I had thought about Russian Vine ( there is no possibility of root spread). I would quite like to use a species of clematis but have no idea whether it would survive this situation (the location is rural Northumberland, UK)
Does anyone have a good idea?
David L
20 May, 2010
Answers
The rule of thumb on bushes in containers: the container should be no less wide and deep than 1/3 the height of the bush. The same is true of vines. If the pot is skimpy, the plants may survive, but they won't thrive.
20 May, 2010
Hi David and welcome to GoY to really answer your question you will find it easier if you join us. No real hedge plant is going to survive in a container 6 inches deep it simply isn't deep enough for the roots to go down. I would imagine the troughs were completely frozen in winter and this meant the pyracantha could get neither water nor air.
Clematis will not be happy in that situation as they need a cool root run and whilst you can plant them in sun and cover the ground with pebbles or something to protect the roots in a trough the heat will still reach them.
I'm no expert on Russian Vines as I would not allow one in the garden but I think you will find they too need a deeper root run.
20 May, 2010