checkout growit gold works it's cheap and it's Australian easy to use and quite good enough to get your point across. Good landscape desighn software can cost thousands of dollars and is usually very hard to use. I used to hand draw designs but now I find growit is just faster once you know how to use it.As Geoff said you need more than software to be a garden designer. There are plenty of Mcdonalds carpark designers around. Three plant knowledge they are all the same. If you want more info on growit pm me