can i buy gardening vouchers on the internet

You could try this site :

http://www.thevouchergarden.co.uk/

I can't vouch for the site as I've never used it. If it is a present for someone I'd maybe check that the garden centres near where they live do accept the particular vouchers you are considering purchasing.

Try going over to the Clydeside Nurseries, they sell gift vouchers, you could also try Dobbies at Cumbernauld, or the huge Dobbies at Dunfermline, huge garden centre and a good day out...

Check out this link......

http://www.dobbies.co.uk/acatalog/Gift-Vouchers.html

Hope this helps....

Paul