In last month’s post, I explained how to use simple layering to propagate shrubs with branches close to the ground.
But what about shrubs that don’t have low-hanging branches? Fortunately, there are other propagation approaches you can use: Dividing root balls, transplanting runners, and taking stem cuttings. Within a short time, you can have several baby shrubs for transplanting around your yard.
Dividing root balls. There are many shrubs that don’t respond well to division because of their tree-like growth habit from a single trunk. But there are other shrubs, primarily those that produce multiple canes, that divide nicely. Examples include butterfly bush, rose, dogwood, spirea, potentilla, lilac and forsythia.
To propagate by division, dig up the root ball of the mother plant. The root ball may fall apart by itself, leaving several cane clumps with roots attached. If not, use a shovel or knife to cut the ball apart, being careful to minimize damage. Make sure that each cane clump has a good root ball. Then transplant the clumps to their final resting places.
Transplanting runners. Some shrubs produce runners, called rhizomes (underground) or stolons (above ground), which create suckers. These shrubs are called colonizers because, over time, they’ll create colonies of themselves if left unchecked. Colonizers include serviceberry, dogwood, lilac, sumac and kerria.
If you want to propagate and transplant a baby shrub from the mother shrub, look for a branch growing several inches from the mother plant—a branch that looks like it wants to strike out on its own. Carefully dig around that branch to see whether it’s attached to its own runner. If you spot a runner, dig it up, coat it with a rooting hormone, such as Clonex, and gently place it in a hole in a pot or in the ground.
If you’re using a pot, mix peat moss with sand or perlite for a loose, well-draining medium. If you’re planting the runner in the ground, dig a trench about six inches deep and fill it with sand. You should moisten your growing medium with water, then poke a hole in the medium with your finger so you can insert the runner into the medium without disturbing the rooting hormone. Then gently backfill the hole. After that, just keep the runner watered the same as you would a regular plant.
Then wait about four months or so to give the runner time to develop auxiliary roots before transplanting it to its new home.
Taking stem cuttings. This approach, in my experience, is the diciest of the propagation methods. So if you can propagate a shrub by layering, division or transplanting runners, I suggest that you use one of those methods instead of taking cuttings.
In spite of difficulties, I have successfully propagated red twig dogwoods from cuttings. But my success rate was only about 60 percent. Professionals have better equipment and are far more adept at propagating from cuttings than I am.
With layering and division, I’ve had a 100-percent success rate, and with transplanting runners, I’ve averaged about 75%.
If you have your heart set on propagating a shrub that can’t be propagated with the other methods I’ve described, then cuttings are the way to go.
There are three types of woody plant cuttings: softwood, semi-hardwood and hardwood. Softwood cuttings are taken from tender new growth in the spring or early summer. Semi-hardwood cuttings are taken from partially matured growth in the summer. Hardwood cuttings are taken from mature stems during the fall and winter.
Different types of shrubs root more readily from different types of cuttings. Daphne and euonymus, for example, propagate most readily from semi-hardwood cuttings. Viburnum, on the other hand, propagates most readily from softwood and hardwood cuttings.
To determine which shrubs require which cutting types, I check my reference book, Plant Propagation from The American Horticultural Society.
When I propagated red twig dogwoods, I took semi-hardwood cuttings in late summer and stripped off all the leaves. Then I dug a trench, filled it with sand, and planted the cuttings the same way I did for the runners mentioned earlier. I then mulched the cuttings with black plastic. The following spring, I planted the cuttings in their final resting places. Four of my seven cuttings survived the winter and transplanting. I used rooting hormone on three of the seven cuttings.
If you want to get serious about rooting shrubs from cuttings, I suggest consulting Plant Propagation for step-by-step instructions.