Scrubs, as in underbrush? If so, "reindeer moss" (a type of lichen) is a popular option and readily available at most craft stores (and online, failing that). It comes in assorted colors, from a pale tan to nearly neon green, so you can easily match different basing schemes/climates. As each "branch" forks continuously along its length and becomes thinner with each split, it also scales easily. The stuff looks like this: