Fine turf

  They are definitely "tree-like", though I don't know if they are like the trees I envisioned them being.  I wanted to try a Black Cottonwood of small to moderate size.

^^^This is what it should look like...

^^^This is what I ended up with...

Kinda spindly and not enough foliage.  So I am now looking for a different armature to attach the fine turf or clump foliage to...

Try This

Natural materials don't always work as-is.  Take pieces of those branch thingies you're using, and attach them to some other armature that will form the main trunk and some of its larger limbs.  I've been using Super Tree material and gluing it to sagebrush with CA, then hitting it with accelerator to form an instant bond.  Charlie Comstock had an article in MRH where he did roughly the same thing, but used plastic tree armatures like Woodland Scenics and attached the natural branches to those.

These are supposed to be cottonwoods, and were built as described above.

Nice Rob

  Those are some nice looking trees!  I am using Caspia for these trees.  I tried using CA to make a bigger bushier tree, but the material must have some type of "stuff" on it, because it didn't stick.  I am trying some tacky glue and will see how that works.  I'll definitely have to order up some super tree material.  

  I'll keep experimenting with a few different things.  I actually think this material would make a pretty credible Poplar if clumped together.  The glue is still drying.  I also want to try some static grass and then apply the ground foam just to see what I get.  

  Right now I am a bit limited in my scenic supplies, both in material types and color selection.

  What would you recommend for a basic kit to building trees for beginners?

Basic Materials

Sounds like you already have the all-important tacky glue.  Having some plain white or yellow glue is always good, and I like 3M Super 77 spray adhesive for attaching foam to trees.

For my prototype and time of year, I'm using Scenic Express "spring green," which works well for summer greenery despite the name.  I have both the regular coarse foam and the newer "Super Turf" with the "open cell" texture.  I use some "medium green" and "dark green" coarse foam from Woodland Scenics for variety, plus I have some various other greens in plastic bags and have lost the labels so am not sure what they are exactly. I also have various shades and textures of conifer greens from Woodland Scenics, Scenic Express, Timberline, AMSI and others.  Even in N scale, I like the look of coarser foam for tree leaves, as the fine foam often looks just like fine foam instead of leaves.  It just doesn't have the right texture most of the time to my eye.  I do use WS "green blend" fine foam to fill in around the coarse on many trees, including those pictured.

I use several different materials for building up bush and tree shapes, including Super Trees, poly fiber, and 3M "synthetic steel wool" scrub pads which can be torn up into all kinds of small bushes, as well as being useful for adding branches to larger trees.  I make sagebrush from them, and some of the other bushes in my photo above use them too.

Did you use CA accelerator?  I haven't had the greatest luck getting natural materials to stick to my trunk armatures without it.  Hot glue can work too.

Sage brush

Armature shape and sagebrush

  I can already tell that I need to really think about the shape of the armature for my tree, as it pretty much defines the type of tree that people will associate with it.  I think if I can get to the point that I can make a bare tree that evokes the type of tree I want to model, the texture and color of the foliage will be secondary.   Currently my selection of foliage materials are: Woodland Scenics fine turf in Burnt Grass, Green Grass and "Weeds".  I also have clump foliage in Forest Green and Dark Green.  Noch static grass in Marsh Grass and Summer Medium Green.

  If it were summertime I would be heading over the mountains to eastern Washington to see what kind of sagebrush we have over there.  Unfortunately there isn't any on this side of the Cascades.

  I'll be checking out some of the companies you have mentioned.  Some I have never heard of before and am sure the local hobby shop doesn't carry!  

Suppliers

Scenic Express is an MRH sponsor, so you can get to their site via the MRH advertiser links.  AMSI should be available through Walthers, but they also may still ship direct (they used to).