The most common form of plant propagation is digging and dividing which is best done in early spring before new growth or in the fall before plants go dormant. Digging and dividing is great for herbaceous plants but those plants that are considered woody ornamentals do not divide as easily with a spade. In this case we can look to the technique of rooting out softwood cuttings from the mother plant.
Greenhouses have stock plants that they maintain from year to year to provide the cuttings for each year’s new generation. We can do this at home on a smaller scale with just a few tools. Grab a pair of sharp pruners, some light soilless potting mixture (like peat and perlite), some small 3-inch pots, a few ziplock bags, popsicle sticks and some rooting hormone (like Rootone). Any variation on the theme will work we just want to be able to create mini greenhouses for each cutting once they are prepared.
June is a good time of the year to propagate by cutting those plants that root out well from ripened soft wood. This soft wood is essentially new, succulent growth that has been allowed to “ripen” but not harden off totally. Think about the new growth of a hydrangea in June: not too soft and not too hard. In fact, I think hydrangeas are one of the easiest to propagate through cuttings and this is what I’ll be doing this year. Give it a try.
Take about a 3 to 4-inch stocky cutting from the tip of a stem. Strip the leaves from the stem except for the top 2 (if they are large you can trim them up with scissors to balance the top to the bottom). Dip the stem into a little bowl of rooting hormone and then into your prepared pots filled with peat and perlite (I use a pencil to prepare the little hole and I moisten the peat prior to sticking the cuttings in). Craft a little greenhouse with your popsicle stick and ziplock baggy (poke a couple of holes in your baggy for a little air circulation). Keep the soil moist, not soggy, using a spray bottle while the cutting is under plastic, until your cutting roots out.
Once rooted you can remove the greenhouse but continue to use a spray bottle to mist your plants. Their roots are still developing so some mist on the foliage provides necessary moisture. Cuttings generally root out better under mist so dampen the soil during preparation but follow up with a mist routine until you take the greenhouse baggy off. Let them mature somewhere in the shade outside and begin to water them as needed (which will likely be often). They will appreciate the humidity of our summers more than the cool and dry conditions of an air-conditioned house, so I prefer to move them outdoors in the shade. As the summer progresses your hydrangea cuttings will mature enough to be planted in the garden by fall.
Some plants root out better as hard wood cuttings so you would wait until late summer to propagate. Hardwood cuttings can be rooted out in a prepared bed (sandy soil and some kind of cold frame rigged up are good here) outside and good candidates include shrubby plants like roses (especially the old-fashioned ones), boxwood and taxus. You can also try the technique of layering branches, stems, or runners to the soil to root out while they are still attached to the plant. Plants that naturally sucker are good candidates for layering, they include brambles, lilacs, forsythia, calycanthus, itea and fothergilla. Sometimes laying happens by accident, a stem will sag to the ground, get covered in a little soil and root out by the end of the season: this is what we want to mimic. You can use a sod staple, brick, or other heavy item to hold the branch down until the soil covered part roots out and you cut it away from the mother plant.