My monster American hornbeam. The trunk base is 6″ in diameter.

One of my favorite and best bonsai trees for beginners is the American hornbeam, or Carpinus Caroliniana. It is a member of the birch family, Betulaceae and is an understory tree, growing to only about 30’ in height.

The bark is gray and smooth, the leaves a dark blue-green and shiny, elliptical, long-pointed at the tip, and sharply doubly saw-toothed.

Best Features

Growth habit: American hornbeam grows continuously from spring through the end of the growing season. This hastens training, as it can be wired and shaped as many as three times during each season.

Leaf size reduction: hornbeam leaves reduce well, from 4-1/2” in length to less than 1”.

Ramification: facilitated by the continuous growth habit. For larger collected specimens with no branches at all, it’s common to see the tree bud and produce shoots that in turn produce secondary shoots in the first year.

This is evident on the specimen pictured here, which was collected in 2010 and photographed a year later.

Root growth: very vigorous. Be sure not to disturb the root zone for newly collected specimens during the first year, to allow the tender new roots time to harden off.

By year two, your hornbeam can be potted into a bonsai container provided you’re satisfied with the development of the branching and no longer need vigorous recovery growth. Once your bonsai is potted, plan on root-pruning and repotting every second year.

Worst Feature

Hornbeams are susceptible to borers. When they emerge as adults from the tree, you get a round hole in the trunk that won’t ever heal, but worse than that you can expect the tree has been weakened and will either succumb fairly quickly or, if it survives, will grow poorly for some years afterward.

There’s no good way to tell in the wild which specimens have been stressed enough to make them susceptible to borer attack, so when you collect hornbeams there’s always a chance you’ll bring home a tree that’s overly stressed.

The good news is, once a tree has recovered from collection and is healthily on its way to becoming a bonsai, I’ve never seen a borer attack. There’s never any guarantee, of course, but it’s nice to have some assurance.

Sources of Hornbeam

American hornbeam is very widespread in Eastern North America, ranging from the Deep South all the way to Canada. It’s found mainly in moist, rich soils near or along streams. Specialty bonsai nurseries also offer hornbeam specimens.

If you collect your own: hornbeam has a stout wood, so I always recommend use of a cordless reciprocating saw to make the work easier.

Cut the trunk to roughly 12-24”, then sever the lateral roots to within 4-6” of the trunk. Next thrust the blade up under the tree and sever the taproot.

Most trees should be out of the ground in under five minutes using this tool.

Once it’s time to pot the tree initially, first wash off all the native soil. Then re-cut the roots closer to the trunk in anticipation of the eventual bonsai container.

New roots will sprout mostly from the cut ends of the larger roots, so dust near the ends with rooting powder. Pot in prepared soil. Be sure to bury the surface roots to ensure they don’t dry out as the tree recovers.

As a final step, seal every cut on the trunk that’s ¼” or greater in diameter with cut paste.

Other Information

Watering: with the proper well-draining soil mix, you can water as often as needed without fear of root rot. Roots tend to grow to the edge of the pot as they extend, making them prone to scorching in the summer. This is reflected in browning leaf edges. Provide shade during the high heat of summer to minimize this problem.

Feeding: either organic or inorganic at full strength during the growing season. No special requirements.

So What Do You Think?

This is a great tree for beginners or even seasoned bonsai artists. But I would really enjoy hearing your thoughts and your suggestions! I’m always happy to answer any questions you have. Just leave your comment(s) below and I’ll get back to you right away.