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What makes a tree a tree and a shrub a shrub? Is it based on its size, or is it based on usage? Perhaps it depends just on the person supplying a reply to the question. Or are there agreed-upon differences in shrubs and trees?

If a person decides to look up the topic in a search—guess what? Some of the resultant ‘authorities’ offer up differing answers themselves. So, how do you know if those short or bushy things in your yard are shrubs or trees?

One long-standing fact is this: “There are many trees that by pruning can be made to resemble shrubs, and many shrubs that by different pruning may be made to produce medium sized trees.” So, does it depend on whether it has a bunch of limbs or just one main stem called the trunk? Or is there a definite set of characteristics that require a person to call plant A a tree and plant B a shrub?

Botanically, there are annuals, biennials, and perennials. The perennials return year after year. Perennials are further divided into ‘woody’ perennials that have a stem that has a cambium layer that forms a new yearly growth ring you can count or a soft stem that dies back annually. But there is no classification as “shrubbery.”

Based on definition and/or ‘usage,’ a tree typically is referred to as such if it has one trunk, or perhaps two or three if something happened to the single one. A shrub is thought of as being short and having many stems—and it may be a ‘woody’ shrub or one that has a soft stem that dies to the ground every winter. Hence, a holly tree can be trimmed to a multi-stemmed bush referred to as a shrub, and a hibiscus, hydrangea, or a baptisia/false indigo that dies to the ground annually can also be classed as shrubbery. If you are confused, I understand, for it depends on usage and its name as used by the beholder. 

A crepe myrtle is a tree. So is a pawpaw. But, if you cut it back to the ground or if it freezes back to the ground and it comes back as six or eight stems and looks like a big bush, do you still call it a tree?

Some do, and some may say, “That’s shrubbery.”

Some woody perennials almost always grow tall and usually have one trunk. No question they are trees. But isn’t that two-foot-tall Japanese maple or that bonsai also a tree? Yet, if we keep trimming and cutting our trees back, they can look like shrubs. Therefore, what are they?

Other species of woody perennial are apt to grow numerous stems with no effort on our part. So they may get anywhere from several inches to several feet tall. Most everyone refers to them as shrubs.

But if we cut away all but one stem and force it to grow taller than it usually would and have a bushy crown like big trees—do we then call it a shrub a tree? 

Many sift the discussion down to this: does it come up with multiple stems from the rootstock or just one stem? It’s a tree if it has one and a shrub if it has many. 

Or is that not necessarily so? I’ll leave the reader to make the final call. So, what you call it must be what it truly is. Therefore, the answer is often based on usage, not on any identifiable laws of nature.

The author has landscaped for over 25 years. Feedback: www.rockcastles.net