Hardy Shrubs for Security
By Mcfinlay
United Kingdom 
Can you recommend a sturdy shrub which would prevent youths congregating below a canopy? The shrubs would receive some daylight, but not a great deal.
30 Sep, 2008
Answers
You could try Blackthorn (Prunus spinosa) or Qui\ckthorn (Crataegus monogyna) Both very cheap if bought as bare root trees. Planted close together would deter most vandals.
30 Sep, 2008
To Jess and Poaannua, many thanks for your speedy response to my question.
Regards
mcfinlay
1 Oct, 2008
Lol...I've had direct personal experience with Berberis..and no I was not the vandal...I had a friend who wanted her berberis hedge removed...and I wanted the plants, I've since moved from the area but have seen the plants and they're still growing. ...the spines enter the skin and break off... causing a painful eruption under the skin...excruciating!! If I ever need a deterent I'm going to plant berberis...good suggestion,Jess!
1 Oct, 2008
Lori
Many thanks for your very useful contribution to my question.
1 Oct, 2008
If not in full sun you may not be able to grow Pyracantha which is the number one deterrent. Might be worth trying.
Next best thing would be a Berberis..Most are spine covered but Darwinii would work well as it is evergreen with tiny spike covered leaves.
http://www.foxglovegardens.com/Assets/Native%20hedging/Berberis%20darwinii.jpg
30 Sep, 2008