The only species of Hydrangea native in Maryland is Smooth Hydrangea (common names may vary, as the linked page calls it Wild Hydrangea), with the botanical name of Hydrangea arborescens. Oakleaf Hydrangea (Hydrangea quercifolia) is native well south of here, despite being perfectly cold-hardy in MD. (Refer to the lime-green county highlights on the linked map. The dark green shaded areas on that map only indicates a species is native to that state, so it's less useful data compared to the individually-highlighted counties where the plant is documented as growing wild.)

To our knowledge, no Hydrangea species is invasive in Maryland, so while many non-native selections are often grown, they are not currently posing a threat to local ecosystems in terms of spread.

There are many cultivars (varieties) of each species of hydrangea commonly grown in Maryland: arborescens, macrophylla (and its look-alike serrata), paniculata, and quercifolia. Within Hydrangea arborescens, the varieties/cultivars closest to the wild type in terms of flower structure are those with the most "lacecap" style blooms. That is, those with very few petals ("sepals," technically) and more true flowers (the blooms in the center of the flower cluster that lack petals), which attract and feed pollinators. We have two very short videos that explain the differences (maybe you already saw them): Smooth Hydrangea: A Maryland Native Shrub and Lacecap vs. Mophead Hydrangea Flowers: What's Good for Pollinators?

Miri