Conifers
I use several commercially available conifer trees. Mostly various brands of bottle brush. I use them for younger trees. For my larger homemade trees, I use several types of artificial braches, stems and fonds found at craft stores like Hobby Lobby, Michaels and Factory Direct Craft.
Here's a couple Styrofoam blocks with a bunch of different trees ready to take out to the layout.
This is an artificial asparagus fern.
This is artificial juniper.
This is artificial cedar
This is artificial fern
This is some dry grass. Can't find it anymore. I think it looks like ponderosa.
This is a different type of artificial fern that I flocked with ground foam.
This guy is cutting limbs as he climbs.