Chinese Juniper, Juniperous chinensis, “Armstrong"
Juniperus is a genus comprised of about 60 species of evergreen shrubs and trees. Junipers are ubiquitous bonsai material, and for good reason. Many species are incredibly tough, they thrive in poor soils and harsh conditions, they bud back well after hard pruning, and they develop an abundance of fine feeder roots easily in a pot.
Juniper has a long history as a bonsai subject, both in China and Japan. Juniperus rigida and Juniperus chinensis 'Sargentii' are the two most prevalent species used there. I personally do not enjoy working with rigida as the needles are incredibly sharp, leaving angry red dots in my skin whenever I touch the foliage. Many other types of Juniper display this gorse-like foliage as well, so beware if you have sensitive skin.
Here in the United States many enthusiasts cultivate J. chinensis bonsai as well as many other species. J. chinensis, or Sargeant's Juniper, has all the qualities that make for an attractive bonsai. Through careful pinching and plucking, one can create wonderful dense clouds of foliage atop a rugged old trunk in relatively short order.
Since the 1940's bonsai enthusiasts along the West Coast have collected and trained their native Juniper, J. californica, into truly gorgeous bonsai. Our own Rocky Mountain Junipers and Common or Field Juniper also make great indigenous material. On the East Coast, Virginia Red Cedar, which is actually Juniperus virginiana, makes for good bonsai, if a suitable specimen can be found. J. virginiana is a lowland tree, most often appearing along fence lines, roadways, and meadows, where birds naturally stratify the seed-- the berries are highly prized by a variety of animals. Thus, in the absence of harsh meteorology and other adverse growing conditions, most J. virginiana grow ramrod straight and sink deep taproots before sending out fine feeder roots. Your best bet for finding a natural specimen to collect and train is usually along the roadside where crews regularly hack back the vegetation. These brutally pruned trees often yield interesting trunks with wide bases and sufficient greenery to survive the collecting process.