Though the subject says most of what I meant to ask, I’ll specify. How do they move? Are they Ents, or trees? How do they kill?
I always think of them as Entish trees.
As far as how they kill, it occured to me a long time ago that one possible mechanism is suggested by the Hobbits’ run-in with Old Man Willow in the Old Forest in Fellowship of the Ring(book, not movie). Not that OMW was neccesarily a Huorn himself, though.
There’s sort of a continuum of sentience in the plant kingdom. At one end, you have trees, just plain trees. At the other end, you have Ents who think, speak, walk around, and do stuff with their hands. Then in between there are the Ents who are getting sleepy, and more, hmm, treeish. If they totally go to sleep and stay that way, you can’t really tell the difference between them and trees anymore. And also in the middle are trees that are starting to become, hmm, ah, hoomm, well, Entish. Starting to wake up. Elves started it, you know. It was Elves who went around waking up trees, teaching them to speak.
The Huorns are trees that became semi-sentient and also developed a power of locomotion and ability to grasp. Not quite Ents, but more than ordinary trees. Old Man Willow is, except for locomotion, a sort of super-Huorn. He may not walk around, but he has the power to alter the topography in the Old Forest. Or if not him, exactly, it’s done by the powerful weirdness of the Old Forest itself, the genius loci, of which O.M.W. is the main manifestation.
The Orcs fleeing from Helm’s Deep ran under the eaves of the Huorn army that had emplaced itself in that position during the night. How exactly they were killed is left to the imagination. (Part of Tolkien’s genius is his way of sketching the outlines of horror without showing all of it explicity—like Stephen King, he understood well how much more effective horror is when it’s allowed to fester unspoken in the dark depths of the reader’s imagination.) I surmise the branches of the Huorns reached down to grab the Orcs that passed underneath, and squeeezed them, yess, my Pre— umm, that was somebody else. But yeah, I think of the Huorns as sort of botanical boa constrictors.
You know where the inspiration for the Huorns came from? When Tolkien first read Macbeth, he thought that would be a superb way for Macbeth to get his comeuppance: the trees of Birnam Forest marching up the hill to storm his castle. But what disappointment! It was nothing but ordinary Men soldiers camouflaged with branches! Shakespeare cheated. So JRRT resolved when he got a chance to create an army of really mean trees, he would do it right.
Don’t forget the Balrog.
My impression wasn’t so much that Old Man Willow controlled the trees in the Old Forest so much as they were all capable of at least shifting somewhat and did so and the Willow just happened to be the most agressive and hostile of them.
And the Hurons I always thought of consuming orcs in the same way the Willow did, openning some kind of cavity and drawing them in. Note that there wasn’t any trace of the orcs when Theoden and the remains of the Fellowship passed through the area. Of course, as you say the exact method of the Huron’s attack is left to the imagination.
Huorns have wings?
TWDuke, duck and run. Duck and run for your life.