I am not familiar with it, adiro, but I am concerned that (a) it sounds like a mophead/macrophylla, (b) you live in Zones 5/6 and (c) most macrophyllas do not do well when planted outside in Zone 5/6 (unless you apply winter protection techniques).

The good news though is that people who live in cold zones can grow some of the recent introductions that bloom on new wood such as the Endless Summer Series, the Forever & Ever Series, etc. as these ones can withstand the cold and thrive in Zone 5 Winters. Charm could be yet another but as you noticed, there is little information about it on the Internet.

Can you determine from the plant label if this shrub can be grown in your zone and/or if it grows on new wood?

To answer some of your questions: part shade means that the shrub gets no more than 4 hours of sun (approx.) per day; this is a requirement in the southern states like Texas, Alabama, Georgia, Florida, etc. But as you move north, you gain flexibility and many hydrangeas can exceed this requirement. When you get to U. S. States that border Canada in the Northeast, many hydrangeas are grown in full sun with little problem; the only concern there then becomes that the plant needs to withstand their cold temperatures and drying winds.

As far as clay soil, I also have clay soil. When planting hydrangeas, I mix organic compost with my soil to improve drainage and maintain a better soil pH than my plain alkaline soil has. I ammend every spring with some soil sulphur or aluminum sulphate to prevent iron chlorosis. If your clay soil is acidic, you do not need to worry about all these chores; just add organic compost to improve drainage.

If it turns out that the plant cannot survive outside, consider growing it in a pot. Use acidic potting mix and water well in the pot. Then bring the pot inside when the plant goes dormant and store in a garage where you can water it once every week or two weeks. Some people also get a cheap plastic pot for shrubs and, during the warm months, they dig a hole and put the pot in there; then in winter, they pull it out & bring it inside, re-potting into a bigger size if needed.

Thank you so much for answering! The info you give me is very useful, as I have not thought about compost at all, I just bought a general rose/tomato liquid fertilizer.

The label says it's hardy to zone 5. Flowers on new wood only. ( I don't know if that's a good thing or a bad thing) I will take winter precautions. I don't think I can keep it in a pot, as the plant is bigger than the bucket it came in and heavy and I couldn't afford a bigger pot, beside that we don't have a garage for winter keeping.

The flower does not appear to be a new variety, as I've found something on internet that says it was a France 1934 variety possibly disappeared that some cultivars (sp?) are still bringing it back ( sorry for my English here)

If I can figure out how to insert pictures, I'll keep you updated on how she's doing,
thank you again!