Shrubs and the Three Bears

Trees grow big roots that spread wide and deep. Shrubs—no surprise—have smaller root systems, but they differ in other ways as well.

Right under the leaf litter is where most of the roots on a freely growing shrub are found. In that soil zone shrubs find moderately moist soil.

Typical root system of a tree: even when young, large roots are present

Typical root system of a shrub: fine, with few large roots

Shrubs may have big roots, but once cut and put in a bonsai pot, they rarely grow big roots again. The maple will continue to grow big roots even after being put in a pot. You far more often reach for the ball cutter on trees than on shrubs to nibble at large roots, once established as bonsai.

What does this mean for bonsai? A shrub’s fine roots, oddly enough, prefer deeper pots. The typical Satsuki azalea pot is a good shrub template: a deep pot, more of a pine pot, really.

A shrub, like an azalea or a quince, has more trouble with the fast and severe cycle in shallow pots of too wet followed by too dry. Fine shrub roots don’t respond well to that. And root rot, especially on holly or azalea, is the common result.

The goal for choosing the right pot, in rough shape at any rate, enhances what the shrub wants, evenly moist soil for its fine roots. You find that in a deep pot—the wide range in the middle that isn’t the dry top and not the wet bottom.

Not too wet and not too dry—sort of like the three bears. The shrub is bear number three.

Note: these are general comments, assuming you’re growing something bonsai-normal like a boxwood, winter hazel or quince, not creosote bush which has roots that run forever in the dry soil.