Welcome - It seems your contest is off to a slow start, As one of the veteran designers here, let me assure you that most entries come in later than soon. Here are some concepts of mine that I believe will work nicely in your contest. Please feel free to offer feedback and suggestions directly by clicking on a specific entry.
The thing I really like about this is the icon. I like the blue and green color - although the shape may be a little too abstract? I don't know if it would be known to be a leaf if it did not have the word "Landscaping" next to it.
I really like that we could use it as a .ico, use it on a mobile app or ipad, etc. I like the "shiny-ness" of it.
I don't know if it is my place to ask or not - but can you play with other shapes within the blue cube? (We like the concept or basic shape on www.Landscaping.com now) or other shapes...