Although hydrangeas do produce seeds, harvesting the seeds can be difficult since the seed is no larger than a grain of salt. Much more successful propagation of hydrangeas can be done by layering or methods of cuttings from a mother plant. As easy as propagating hydrangeas can be, the process is not without problems.
Problems With Layering
Propagating your hydrangea by layering involves selecting a strong, healthy branch of your existing hydrangea bush and, basically, laying, or securing, it on the ground, while the branch is still attached to the main "mother" plant, so roots develop from the branch and create a new plant. This process can take several months before a new hydrangea plant forms on the branch. The main problem gardeners experience with this method of hydrangea propagation is in successfully transplanting the newly formed plant. To transplant, you must sever, or cut, the new plant from the original branch of the mother hydrangea plant by cutting the connection. Because the new plant has been depending on the mother plant to supply the bulk of its needed nutrition, the young plant experiences shock once disconnected. Adding the stress of immediately transplanting to the young hydrangea plant may ultimately kill it, and at the very least, set its development back. Leaving the new plant in its original location for 3 to 4 weeks after severing, or cutting, it from the mother plant before transplanting allows the small hydrangea to begin feeding from its own root system. The delayed transplanting will give the new plant time to strengthen and diminish stress.
Problems With Stem Cuttings
Stem cutting hydrangea propagation is most common among gardeners because it is the fastest and relatively easiest method of growing new hydrangea plants from existing bushes. There are several methods to chose from, but all involve cutting a piece of stem, usually a new growth tip, from the existing hydrangea, then potting the cut stem in a growing medium to establish roots. Propagating hydrangea stem cuttings is not without problems, no matter what stem cutting method you chose. Location of your newly potted stem cuttings is a key element to success. Placing the potted cuttings in direct sun will kill them; shade is ideal. Over or under watering is the next problem with propagation hydrangea cuttings. Too much water will create soggy soil and your hydrangea cutting will take longer to root or may rot and die. Allowing the soil to completely dry out in newly potted cuttings will also kill the plant. Monitoring the soil so it is an even, damp moisture level is ideal. Daily misting of the cuttings for the first week, and every few days thereafter, is also recommended.
Problems With Root Cuttings
Although propagating hydrangeas from root cuttings is often used, if not done correctly it can cause serious problems not only for the success of propagation, but for the original mother plant. The time of year you harvest the section of root from the mother plant must be while the plant is still in its dormancy period. Late winter or early spring are ideal times to start a hydrangea from a root cutting. Damage can occur to the mother plant if the plant has not reached maturity of two or three years. Taking a root cutting from a young, immature hydrangea bush can shock the mother plant, particularly if the cutting is extracted during the growing period of the plant.