Alabama native species are Smooth Hydrangea (Hydrangea arborescens) and Oakleaf Hydrangea (Hydrangea quercifolia). They are not invasive plants.

He probably brought home Oakleaf Hydrangea if you think it looks like Tardiva.

I'm sorry if you think that native plants are more likely to be invasive than any other plant. Most of the "invasive" plants you see in the wild are non-native plants that have naturalized (like Kudzu, privet and the yellow/white honeysuckle).

Thanks...I found pictures on the web and they look just like the Oakleaf Hydrangea.
Planting them in the background of a flower bed.

I have 3 of the 4 native species of Hydrangea, Oakleaf (H. quercifolia), Wild Hydrangea (H. arborescens), which is the parent of 'Annabelle' & a pink-flowering form of the Silverleaf Hydrangea (H. radiata).
All were grown from cuttings from wild plants or from a GNPS Rescue site (H. arborescens).

None have ever exhibited a tendency to become invasive (I wish they would, a teeny bit, so I wouldn't have to root them)!

Hydrangea paniculata (like your 'Tardiva') can potentially become an invasive plant. The "panics" have escaped cultivation and can be found in the wild all along the Eastern seaboard, from NC to ME and into Canada (ON).

"Hydrangea paniculata (like your 'Tardiva') can potentially become an invasive plant."

If last year I would of read such statement I would of jump of my chair :-)
Not this year- found a lot of seedlings in close vicinity to one of the Limelights. However, I'm not 100% sure that they are actualy seedlings or just self-rooted pieces and bits from the last year pruning.