There’s a surprising amount of water on those platforms: waterfalls coming from high up in the tree, little lakes, irrigation channels for the fields. So, we’ll need water. I tried a bit of free-form crochet to come up with this little pond:

Again I used two yarns taken together, a solid turquoise cotton/poly blend and a blue variegated sock yarn:

I basically crocheted a spiral in the round, making wavy lines by changing stitches from single crochet to half-double to double and back, filling in the holes from previous rounds while trying not to get too regular. The pond measures about 10*13 centimetres. Here it is on the platform, surrounded by the beginnings of some tall grasses: