Red Osier likes moisture so I think a little supplemental watering (if dry) would certainly help it grow. They must like the spot if they sprouted there so I think you should be fine. They are a good choice too because they can take some pretty severe pruning, which you'll want to do periodically to have the 'reddest' twigs possible.

All in all, I'd say red osier will be a fine choice for your purposes.

Thank you ernestM.

Do I understand well your answer in concluding that, as long as their is enough soil wetness, it will be easy to get the height needed. Competition with other plants (mainly surrounding trees), light conditions or soil composition would be less important factors.

I'm im a very different climate zone than you are but Red twig dogwood does well here, I have a "thicket" on the north side of my house. It definitely does not like dry conditions but it does need drainage. Don't plant it where it will be in continuously standing water.Take a clue from where it naturally occurs in your area. The ultimate height the plant will reach depends on how closely to "ideal" the growing conditions are. Volunteer plants showing up in your yard is a good sign.
Good luck!

For what it's worth -- I have a massive amount of red twig dogwood growing on my property. The tallest is a good eight feet. A lot of it is concentrated along a natural drainage ditch that leads to a pond on my property and from that fact I conclude that it must not mind being wet and seems in fact to prefer the wet ground. But I also have some growing closer to the house on a well-drained slope.

I therefore conclude that it isn't all that fussy about moisture.

The very uppermost branches of my tallest red twig dogwood shrubs are just as richly blood red as the rest of the shrub. I could just be fortunate in the strain I have growing here though.

This shrub is also well loved by birds; they strip the berries as soon as they ripen.

A warning -- it does get very shaggy and will need a good hard pruning every year but in my opinion this is only for the purpose of having it appear to be well maintained and not for any other particular reason that I have found.

Oh -- and it is extremely easy to propogate. In early spring (April) when the soil is mushy I just chop off a foot or two and put it in the ground where I want it to grow next. No rooting hormone is required for it to succeed wherever I put it.

Thank you, nmgirl and LauraMich.
These are usefull informations that reassure me that red osers are a good choice.