A professional gardener should be charging a minimum of £15.00ph.
I remember my accountant telling me many years ago, if you raise your prices by 20%, 90% of your customers will agree to the raise and the remaining 10% you can afford to lose.
I am aware of the economic climate at the moment and trading is not easy so every business must set it's own charges according to their circumstances.
But, a rule of thumb is: if you work on the basis of there being 2000 chargeable hours in a trading year (i.e. 50 weeks x 40 hrs - assuming a two week holiday) and you want to make a minimum of £20,000 salary (not unreasonable) this equates to £10.00 ph.
Add tax of circa 25% which equates to £2.50 ph, vehicles costs and sundry costs we can easily eat up £15.00ph.
I would like to see a basic wage for a self employed gardener.