Timber!

Sometimes these quick little posts represent a lot of work.  This isn't one of those times.  My forests took a total of around four hours start to finish.  I'm a fan of the Toob Trees for my wargaming needs.  They are a little undersized, but at a buck each for durable plastic that takes paint like a champ they are hard to beat.

Splintered Light 15mm Barbarian for scale.

Since these will be used on my skirmish table, I mounted them individually on metal washers.  These both provide weight and a little more size to help the trees stand upright, and give me a chance to paint and grass/flock them so that they blend into my terrain shapes a little better, too.  

The pine tree nearest the camera here has a larger base constructed of a pre-cut wooden disc.  These were used in a few cases to allow for the addition of a few rocks and logs to add to the variety of the trees.  This is my go-to system that allows for dense wood terrain pieces where you can move the trees around to allow unlimited movement of figures within the base, and adds the flexibility of using the trees individually as well.

By varying the painting styles a little, you can get a uniform look with just enough variety to help the trees stand out a little better.  I don't know if it shows up in the photos, but in this case every tree has the same base green, but I used three different mid-tone shades on them.  Then I used two different highlights (bone white and an ochre yellow) for a total of six different looks on the trees.  Using different weights of dry brushing provides for even more variety.  Trust me, these trees don't look nearly as white in person as they do in these shots.

My storage solution is a pair of flat plastic boxes.  Just a little something to keep them from banging around too much.  They have a matte varnish sprayed on to protect them, but every little bit helps.

These should work equally well in my sci-fi games as my fantasy games.  Which means I may have to reorganize my terrain boxes.  I think maybe I need just one 'generic terrain' box, with separate boxes for sci-fi and fantasy touches...