How to Propagate Oakleaf Hydrangeas
The Oakleaf Hydrangea (Hydrangea quercifolia) is a large shrub native to the southern US that grows in partial shade in moist acidic soil. The oakleaf hydrangea has flowers that are long panicles, unlike the mophead flower that is seen on most ornamental hydrangeas. A unique feature of oakleaf hydrangeas is that new plants or suckers come up from the roots surrounding the plant and they can me separated from the mother plant and relocated to a pot or another part of the garden. Another way to produce more oakleaf hydrangea plants is by taking a cutting and rooting it in sterile potting soil or other planting medium.
Take a 6-inch cutting from the end of a non-blooming stem in early spring that has a swollen bud on the end and two small leaves growing from the node underneath the new bud. Immediately place in container holding water. Do not let the cut end of the cutting be exposed to air for more than a few seconds.
Prepare sterile planting medium. Use new potting soil, sand or a sterile potting mixture that is used specifically for rooting plants. The potting mixture should not contain any fertilizers. Do not use garden soil or old potting soil because it contains pathogens that will attack the new roots that form on the oakleaf hydrangea cutting. Add potting medium to flower pot then soak potting medium with water. Let drain.
Cut oakleaf hydrangea stem with a sharp cutting tool just below the leaf node that is below the node where the two small leaves are located. This will make your cutting about 3-4 inches long. Pull off the buds or leaves at the leaf node that you cut underneath by using a downward motion. This will damage the stem slightly so the rooting hormone will stick to the area where new roots will form.
Dip cut end of stem in water then dip in powdered rooting hormone covering the end of the stem and the damaged leaf nodes where you removed the leaves or buds.
Make a hole in the planting medium with your finger. Stick the oakleaf hydrangea stem cutting into the hole deep enough so the soil level is halfway between the cut end and the two small leaves you left on the cutting. Only the two small leaves and the top bud should be visible above the soil line. Be sure the damaged nodes right above the cut or covered with soil. Gently close the planting medium around the cut end. Set pot in a warm (75-85 degree F) area and keep the soil constantly damp, but not wet, for 6-8 weeks until cutting is actively growing.