I quit the extra protection after a few years, when it had gained more size and stems. I did more of a wrapping on the cage around the shrub, to break the cold wind which blows all the time in winter. I worked at a warehouse at the time, so we often had the saran-wrap type plastic on pallets of boxes. It was clear, tall at about 48" high, and with only one cut to open the pallet, ends overlapped on the cage. I used string over the plastic to hold it up on the shrub cage for winter. Usually took a couple or three strings if cage was tall. I have hay bales, so binder twine was easily available for that. Shrub had lots of shredded oak leaf mulch over the roots, piled into the cage about 5" after wrapping, but not deep enough to cover the sticks. Again, more of a wind break than anything else. I liked that the plastic wrap could let the sunshine get on the sticks. I think plants always need sun, and no cover on cage top to hold in any heat. Nothing I did this wrapping on, sprouted early or died, so I put method down as "successful" in protection. The Oakleaf has done just great without the protection since then. Little or no frozen branch ends, blooms reliably each year. Winters have been VERY cold, warmer, wet like this last one, shrub does fine. Probably the cage and wrap was overkill, but I REALLY wanted that small plant to survive! So I was willing to put in the extra time doing the wraps. Cage was big enough to not have branches rubbing in any wind from the top. At the time I thought Hydrangeas were "delicate" and needed that kind of care. Learned more since then, and only one expensive Japanese Maple gets a cage and wrapping now! More because the DOG finds it irrisistable to chew on when snow is deep. Hydrangeas of all sorts do just fine left alone in winter.

Thanks this was a helpful thread. I have not looked on Houzz for this kind of content before. I too find these dwarf plants are not very dwarf and need pruning. Here in Pacific NW pruning these kinds of hydrangeas (Oakleaf) is easy and its harder to screw up the timing and lose the flowers unlike the mop head hydrangea. Oakleaf also need less water so that is ideal. I was just at a garden this morning where their mature Oakleaf had simply eaten the entire front foundation planting. It was hacked back to a 4' high clump but we are going to replace it since it is crowding out a native ribes. I am going to recommend Munchkin and assume that with pruning it can be maintained at 4 x 4. I do love the smaller flowers and the bark of Sikes Dwarf however. Z6-8 Photo is probably Snow Queen. It layers so beautifully. Any thoughts between choosing Sikes Dwarf and Munchkin anyone?

It looks like Cercospora leaf spot, a fungal disease that is very common on nursery grown plants. Generally, once established in the landscape, the disease will eventually disappear. Make sure all diseased foliage is cleaned up and discarded in the fall, provide good air circulation and avoid overhead watering. It is not considered a fatal affliction but it can weaken small plants if the infection is severe. A fungicide may be appropriate to keep the disease from spreading to clean foliage. Daconil is one that is registered for this purpose or you could attempt some more organic approaches like Neem oil or baking soda. Oakleaf hydrangeas are pretty tough plants, but in your colder zone, I'd certainly consider winter protection for this plant. Especially considering its size and that it may be somewhat weakened by disease issues.

I am not aware of any variety or cultivar of Hydrangea quercifolia considered to be any more winter hardy than another. Virtually every source you will find, including Dirr, lists them as a zone 5 plant regardless of selection, but not lower. That is not to say that the siting of your Ruby Slippers isn't being influenced by whatever microclimate may be available in that location that is allowing it to survive. But I couldn't speak to the same degree of success with any other placements nor if your current Ruby Slippers will continue to survive your winters and thrive. Maybe.......maybe not :-) And maybe your zone is not as severe as you think or is undergoing some modification that is making winters less harsh. But at best I would consider it to a be a marginal plant for your area. The best thing about oakleafs growing in colder climates is that they will almost always flower. Even though flowers are produced on old wood, winter cold does not appear to have the same damaging effect on latent flower buds as it does with macs. Stem dieback from cold is a different matter - that can and does happen in colder locations - but if the stems survive the winter (no dieback), chances are very good that they will produce flowers.