I dabble in 15mm sci-fi gaming and lately been using my models as proxies for Beyond the Gates of Antares. Getting terrain together can always be a bit of a chore and at times heavy on the wallet. You can get lots of railroad, medieval, and WW2 terrain easily, but sci-fi stuff is somewhat of a niche market. So inevitably I get to tinkering around making my own.
Vegetation is always something tricky. A really good source is simply aquarium plastic plants, but I decided to try and go the full craft route and thought of working with straws. By melting them partially, they fold open and get this weird pitcher plant type of look. I used a lighter and carefully melted the plastic passing it over the flame. I would also put a little heat on sections of the straw and carefully bend it some to give them a few kinks. Be mindful not to apply too much heat, otherwise you’ll end up burning another hole into the main section of the straw.
A word of warning, too much heat and your plastic straw will catch fire. Not to mention the fumes are toxic as hell, so do this in a well ventilated area (I also had a fan behind me blowing the air away). After melting the ends of the straws, I used hot glue to mount them to some plastic card as bases. I then gave them a coat of primer. I tend to have trees and the like on individual bases so I can move them around. When painting them up I used primarily a green base coat along with some highlights of bright colors to draw out a lot of contrast.
Thrown on some felt, they make for some decent vegetation that is a little different from your typical plant foliage. A pretty easy project and if given a more diligent paint job (compared to what I did), you can get some great looking plants.
Side Note: For 15mm terrain, straws can make for some decent obstacles too. Stacked and lined up, they can serve as large metal or concrete culvert pipes.