Propogating Hydrangea from Cuttings

Taking the Cuttings
The first thing you'll need is a healthy hydrangea bush with new growth (green stems).You should get 5 or more good quality cuttings from one stem. Early morning is the best time to take them, although any time they're not wilted is OK. Make sure to label them if you want to know what you are growing. You can place the stems in the fridge overnight if you can't get to them right away. They should last several days, though if you are planning to wait awhile I would strongly suggest trimming the cuttings (see below) before storing them in the fridge.
Rooting Media
You will need 1 part peat/potting soil and 1 part medium to fine grade perlite, vermiculite (expanded lava), or sand. If you have access to mason's sand or screened sand I would strongly suggest using it instead of the perlite. In fact, many propagators will use 100% sand to ensure excellent drainage with their automated misting systems. Mix the perlite (or sand) and peat moss together thoroughly and fill the propagation trays or small pots to the top. The next step is very important... soak the prepared tray in a cake pan or sink filled with water to nearly the top of the propagation tray for at least 1/2 hour, gently spraying the surface occasionally. Wetting the mix prior to potting can eliminate or minimize this phase.

This will avoid dry spots in the middle of the rooting media which may result in failure to root. This "hydrophobic" phenomenon, where the media appears wet on the surface but dry on the inside is why commercial potting mixes use a wetting agent. You've probably seen the same thing when watering a potted plant that's gone too dry... it just won't take water unless you fuss with it. One of the reasons I prefer a heavy percentage of sand in my mix is because I can tell by weight and appearance if your trays are too dry. Sand seldom appears wet on the outside while having dry innards, but will dry a lot quicker than a mix with some peat. The ideal rooting media for most people will have excellent drainage (Perlite or sand) with some ability to retain a little moisture (peat). I use 60% native Nantucket sand (not from the beach, too much salt) and 40% peat, and have been able to over winter fully rooted cuttings "stuck" in late fall right in their propagation trays.
Trimming
The next thing you'll need is a pair of scissors or clean, sharp, pruning shears to trim the cuttings. The idea behind trimming the leaves is to reduce the demands for water while the plant is rooting and to avoid overcrowding in the propagating tray. I like to leave about 2 square inches per leaf to assist the plant in photosynthesis. I've rooted plants without any leaves which takes longer and increases the chance of bacterial and fungal infection. You may want to wash your scissors off in a 5 % bleach solution (straight Clorox), the only time I bother is when doing hundreds of cuttings of different cultivars. I like to cut nearly perpendicular to the leaf veins

to maximize the efficiency of the remaining leaf tissue. For the smaller terminal leaf pairs I pretty much cut in half across the long axis
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The next step will be cutting the stems to fit in the tray, including at least one leaf node or terminal bud per cutting. The leaf node is the diamond shaped spot just above where the leaf attaches to the stem. At this time of year most nodes will have a bud developing at this site. These buds will likely begin to develop or unfurl while the plant is setting roots in the tray, leading credence to the old gardeners saying that "new growth follows the knife". They will be next years flowers so take care throughout the entire process. The "terminal" or "apical bud" is the actively growing tip of each stem.
Being careful not to damage the buds, cut across the stem just above the first set of nodes from the bottom.

This first cut will be the top of the first cutting and often the bottom of the next cutting up the stem. Most cuttings will have a pair of nodes and are commonly called "butterfly cuttings".

The wonderful ability of the plant cells to initiate growth when environmental conditions are challenging along with the genetic trait of "differentiation" expressed when the cells on the stem change into "adventitious" root cells make the entire propagating process possible. Leave between 1 and 2 inches below the leaves for sticking into the rooting media.

When you reach the tip of the stem, leave the terminal bud attached to the cutting directly below.

This terminal cutting will be the most vigorous of the cuttings obtained from one stem, but will only produce one flower unless pinched back right after roots are set. I've often used this pinch to start another plant. Another type of cutting which can be used to get more bang from your buck is the single-eyed cutting made by splitting a butterfly cutting right down the middle vertically.

I don't recommend it for the novice because of the high risk of infection. If you really must, you might want to cheat like I do and wait to roots are establish before slicing the plant in 2. Only one flower per plant on this type.
"Sticking"
Now you are ready for the fun part, "sticking" the cuttings into the prepared, fully saturated propagation trays. For best results I suggest picking up a small bottle of rooting hormone .
Dip the bottom of  stems in  rooting  hormone be careful not to get to much on each cutting. Hydrangeas will root OK without hormone but root faster and more evenly with it. and then stick each one in the center of a propagation cell up to the hilt, or base of the leaves.

 Avoid having any of the leaves touching each other, as they might rot (this might drive you a bit nuts with larger cuttings).

Misting, The "Art" part
Once all your cuttings are stuck, they will be ready for their first "myst" er mist. A Windex bottle works fine if you are like me and don't own an iron. If you are a well equipped gardener and plan to raise your plants outside you might have a "misting" nozzle on the hose already. I like to "water the cuttings in" on my first mist, spraying them until grains of media run into the sockets where the stems are, but being careful not to over water (media starts running out the holes in the bottom of the cells and over the top like the picture below).

Thereafter, I spray them just until the entire plant is wet, or longer if the media has dried out.
Location, location, location.... Actually a lot depends on you. How often can you mist them in the course of a day? How hot/cold is it where you live? Will You be around to cover them during a sudden downpour or bring them in from an early frost. If the cloudy day turns bright sunny, can you get to them before they dry out? Ideal temp is 60-80 degrees F, how close can you get?
You will have to chose what works for you. I've had success in a very shady, protected (wind will dry them out as well as sun) corner of the garden where I misted them only once or twice a week after the first few days. I recommend misting at least three times a day for the first week as long as they are not in direct sun or wind. More is better if you are around because then you can keep them in a bit more sun. If you are raising them in an air conditioned room you may get away with more sun/less misting. The point (Art) is to never let them dry out or wilt too much before their next misting, balanced with not letting them get to wet. Let them stand dry as long as they are not wilting. If you grow them in deep shade or keep them too moist they will take longer to root and have more time to become infected by a bacterial or fungal disease. Don't mist late in the evening if possible. A windowsill is fine as long as the sun's not too strong. Let your intuition guide you and don't be afraid to experiment, try another type of plant. Your cuttings will become stronger after the first week and require less care. You'll see new growth after 2 weeks. By the end of week 3 you will feel resistance when pulling on the stem,... You can't help yourself, you pull one out... and it's covered with dozens of new roots. A week later the roots have filled the cell and they're ready to transplant... You're HOOKED!

Enjoy!