‘Division’ of Just One Old Shrub Can Yield Bushels of New Ones

Any shrub that forms suckers, which are new shoots that sprout directly from the roots, can be propagated by “division.” Division is easy and quick, because new plants already have shoots and some roots when they are separated from their mother plant.

Examples of suckering shrubs include spirea, kerria, lilac, oak-leaved hydrangea, Siberian dogwood and fragrant sumac.

The best time to divide any shrub is just before growth begins. Start by digging up the plant. Push a sharp-bladed spade into the soil a few inches away from the clump of stems, with the blade angled underneath. Work from all sides, and as you go, push down on the handle of the spade to lever the root ball up.

Once the shrub has been dug up, separate the clump into pieces consisting of a shoot and roots. Do this by spreading the branches so you can look down into the clump, then chopping down into it with your shovel or, if necessary, an ax. Some shrubs have horizontal, underground stems that can be cut free with just a lopper.

If the shrub is very old, save only root-and-shoot pieces from the outer edge of the clump. These are the youngest and most vigorous, so they make the best new plants. If your shrub is not too old and you just want a few new plants, dig up a few shoots from the outside of the clump without disturbing the plant.

Inspect pieces for replanting and recut any torn roots or underground shoots cleanly with pruning shears. Shorten stems if they are so long that the new plant will be unsteady in the ground. Also shorten any lanky roots that would not fit conveniently into a planting hole. Keep roots from drying out by covering them with wet burlap.

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Depending on how many intact roots you are able to retrieve with each piece, your new plants may need coddling for a year in a nursery row before replanting in a permanent location. In any case, dig a hole large enough to accommodate the roots, then spread them out in the hole and backfill soil.

Finally, give each new plant a thorough soaking to settle it in the ground. Keep weeds at bay and provide water as needed in the months ahead, and you will have sturdy plants by autumn.