Grey dogwood never gets tired of sending up suckers, the suckers eventually get as big as the plant. So unless you want a gazillion plants in one spot, you have to remove them.

What you do it dig down about 6 inches or so, a few inches away from the sucker. You'll find a very strong horizontal root running in a straight line--the main plant sends up new suckers along that line. It's easy to see, because the suckers are often lined up in a row. If you want to slow the plant down, dig up that whole horizontal root.

Each sucker will be easier to establish if it has a part of that root along with its own root system. The sucker's own root system will be rather small. Plant as for any bare-root tree or shrub--dig a hole or slit just big enough for the roots, don't amend the soil, firm the soil very well around the roots, water well, and keep the area well watered for the entire first growing season.

If you're going to dig and replant these, do it before the weather gets too hot.

Thank you Elaine. How long have you had your gray dogwoods? Do they seem to get worse over time or do the suckers slow down as the mama shrub matures? They're pretty fast growing. I just don't want them to choke out the other stuff that I've planted along my shrub row.

They never stop. I'm not complaining. Any plants I can't use I donate to the local arboretum.