Anthony,
I am a landscape architect but will declare upfront my interest, as I am also Product Director at Keysoft Solutions who develop KeySCAPE landscape software.
In 2015 we acquired LandCADD and will soon be releasing a version that brings the best of both applications into a single, harmonized solution that will provide the springboard for significant future development. We offer both a version for full versions of AutoCAD (not LT) and a standalone version that is powered by the AutoCAD (2016) OEM engine, which we license from Autodesk. As such, you do not need AutoCAD to run the application and it opens and saves in native DWG formats. We offer both perpetual and term-based (rental) options.
Take a look at http://us.keysoftsolutions.com where you can request a trial download.
