Along with marketing, don't forget to develop and promote your advantage. Here's one you can use ... focus on quality and individualized customer service.
The big lawn care companies have alot of expenses. Time is money to them. The focus is on being fast. Perhaps too much focus. With smaller walk behind mowers you can provide quality cuts that don't tear apart your customers lawns. You will also be more enviromentally friendly. Quality ... service ... eco friendly sounds like a winner to me.