Q: Can you explain the various names for elm, such as slippery elm, hard elm, red elm and so on?

A: Let's begin with the basics. First, hardwoods are trees with leaves and softwoods are trees with needles. As elms have leaves, they are in the hardwood grouping.

Next, elms are divided into two groups: hard elms and soft elms.

Soft elms include two species, American elm (Ulmus americana) and slippery elm (U. rubra). Hard elms include four species: rock elm (U. thomasii), winged elm (U. alata), cedar elm (U. crassifolia) and September elm (U. serotina). Most elms have several different common names. For example, slippery elm also is called red elm, gray elm, soft elm, plus a few very local names. The soft elms are softer than the hard elms; for example, slippery elm hardness is 860 pounds, while rock elm hardness is 1,320 pounds. Hard elms also are about 20 percent denser and stronger.

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