Hydrangeas propagate very easily from cuttings or, as your Mom suggested, by ground layering (there is even something called "pot layering"). With ground layering, you bend a stem downwards into a small (1-2") hole in the ground, scrape lightly the bark (roots will develop there) and lay an object (rock, brick, etc) on top the stem to preventing the stem from rising back up. Then you cover with soil, keep it evenly moist and wait. You can also propagate with cuttings (best results with cuttings taken in April thru summer) but really, a-l-l methods are veeeeeery easy and you can read details here:

http://hydrangeashydrangeas.com/propagation.html

I you decide to propagate via cuttings, I would keep the cuttings inside during winter, maybe in a place where you can see them often (so you will notice when the soil is drying out).

Do a "find" in the forum for keywords like "cutting", "layering" etc. and read more posts on those subjects. Above all, have fun propagating!

You may find that a cutting taken now, planted in a pot after being dipped in rooting hormone, given bottom heat and a loose plastic cover, and kept inside in a bright (but not directly sunny) spot for the winter will root. I've had PeeGee (Hydrangea paniculata) root indoors over the winter.

If you can wait until next season, it will be easier to do layering next growing season.

Thanks for the advice. I'll give it a try!

Honestly hydrangea love our PNW climate. I just take cuttings with good mature wood in the late fall. I take 4-8" of wood, with one or two top set of leaves. If two leaf nodes, I cut all the leaves off the lower node area and 2/3 of each leaf off the top set, so there is less dehydration stress. The poor angular cut leaves makes the method look brutal but works best. I put a scrape line on about 20% of each stem lower section by lightly drawing a scissor blade at 90 degrees across the bark to expose a little green cambium layer on one side. Cuttings are not allowed to dry much (so keep out of sun once cut). I then stick the prepared cuttings directly into either good potting soil or yard soil with 50% commercial yard compost added. We haven't needed to use rooting hormones.

If two nodes are present, the lower node is set at soil level or no more than 1/4" below. Often these ground level leaf buds do best for cuttings overwintered outside. I'll put one to three cuttings into a gallow pot or several 5 - 7 in larger pot. Most cuttings root and thrive, unless the stems were too small in diameter. Often both nodes areas grow, which next spring gives 4 branches and a quickly expanding plant! One gallon plants done this way often bloom the next summer, looking like a Florist gift plant. If planted in a favorable spot it takes 3-4 years here to reach mature sizes! I've seen 'Blue Wave' go from a gallon pot to 6' x 6' beauty in 4-5 yrs.

Just went outside to see the cuttings started this late October. It's been below freezing and so most of the mature leaves have dropped off. But the buds look healthy and there is some growth on above freezing days, especially from node buds at near ground level. Just under freezing again last night, the cutting pots are still frozen at 11 AM. Note the top buds look healthy and are waiting for warmer weather.

We seem to have an ideal hydrangea climate here. If I prune branches after leaf drop and just jam 1-2' stems around the plant drip zone, with no other care, about 20% root and grow. When I forget to rake out ~2' branches and find them still laying flat on the ground, often a few in shady or part sun areas have rooted and are growing nicely.

Based on these experiences, I suspect that colder climates might work just as well using unheated greenhouses or cold frames.

We do have to use slug bait here to protect cuttings and young plants.

Thanks for the information! it's very helpful. I'll give it a try!