The first thing that comes to mind is using Symbols for the garden designs. Gather up all the clipart you have (or can get online) and use those clipart that are similar in style or can be edited. Make a symbol for each.
This would let you reuse them at different sizes. Also making a modification to the symbol would adjust all the instances of the symbol in your design. Maybe the best part is you can use the symbol(s) with the Graphic Hose to spray various garden graphics at once, like a flower bed or wooded area.