For all hydrangea propagation, start all cuttings in pots and either pot them on or plant in the garden at the beginning of their third year.
Taking hydrangea cuttings is really easy and you can expect at least an 80% success rate – although some species are easier than others. Hydrangea propagation is greatly rewarding; be ready for some failure and be tenacious until your propagating skills improve.
H. macrophylla, H. macrophylla ssp. serrata, H. involucrata, H. scandens – by softwood cuttings and semi-ripe cuttings. All very easy. Just take a main growing stem, about 8cms, (not a side shoot) with 3 pairs of leaves. Trim off the two lower pairs of leaves, cut the stem immediately through the lower leaf node, dip the cut stem in rooting hormone powder and place in a good, damp potting compost. Keep humid by using a soda bottle. Keep the soda bottle in place for 4 or 5 weeks, by which time the cutting should be rooted. No need to water during this time as the soda bottle prevents any moisture loss. These cuttings can be taken from June to August – maybe even later if you can provide bottom heat (heating mats).
H. paniculata – by French layering. In early winter, pin down stems horizontally along the ground. 18 months later, where upright shoots have reached 10cm, separate the individual plants and pot on.
H. arborescens (including popular cultivars ‘Annabelle’ and ‘Grandiflora’) – In May or June take a runner (whilst still small), and pot up. No hormone powder necessary. Again, I find it helps to use the soda bottle. You should get 100% success rate.
H. anomala ssp. petiolaris, H. integrifolia, H. seemannii, H. anomala ssp. petiolaris var. ovalifolia (climbing hydrangeas) – by layering. Very easy, just like taking a cutting of English Ivy. Long shoots will self-layer if growth is directed along the ground in Spring and pinned down. One year later, when it is rooted and upright shoots reach about 10cm, separate individual plants from the parent plant and pot them up. No hormone powder necessary, no soda bottles necessary. You should get 100% success rate.
H. aspera, H. quercifolia– These are much more difficult and I only get a 20% success rate with cuttings – or lower! The problem is that they do not appreciate being kept humid, so don’t use the soda bottle method. This creates the problem of keeping them slightly moist but avoiding them rotting. They are slow to establish roots. June and July are the best months. Perhaps a better method is to separate suckers from the parent plant in July and pot them up. Unfortunately, suckers are few and far between so quantity of propagated plants is low.
H. heteromalla – softwood or semi-ripe cuttings can be taken but in our experience the success rate is low. This is the only hydrangea species which we have successfully propagated by collecting and sowing seeds. Unfortunately, this method of sexual reproduction does not protect the genetic purity of named cultivars and therefore their unique phenotype characteristics may be lost. The seedlings we achieved were highly variable.
For all the cuttings I take in May-August I do not use the greenhouse, I just keep them in a shady position and avoid direct sun.
It is possible to take hardwood cuttings in the winter, but the success rate is so much lower.
~ ~ Know your plant names so that you can apply the correct hydrangea propagation methods ~ ~