Add some service.
This year we are excited to provide enhanced service to your property. We will now include (pick something) spring and fall aeration, monthly lawn care tips, easy credit card invoicing, our new "best in the industry commercial mowers" or what ever you may choose. Your new rate is XXX, only a few dollars more, but I'm confident you will see the advantage. Please call if you have questions.
As I'm sure you know, the cost of fuel and materials in maintaining your landscape has gone up in price substantially the last couple of years. We at (your company name) must pass some of these costs on to our customers in order to continue to provide the quality service you have been used to. Your new rate will be XXX starting 3/1/13 (pick a date) Our 1st service will begin the week of xx/xx/2013 . Thank your for your continued support of (your company name) and call anytime to discuss your service.
This way, if the cost of fuel does go down again, you have not just tied the price increase to just fuel cost.
My wife said "you're on lawn toy restriction"