I believe this is Hydrangea quercifolia (oakleaf hydrangea) because its foliage is shaped like oak tree leaves.
In the drawing you can see the mix of sterile and fertile florets, specific to Hydrangea. The bigger florets have an inch or more across and they are always sterile, their role is to attract pollinators. The fertile ones hide behind them, are small (two to four millimetres in height), unspectacular, in big number. Thus the bees and the flies that pollinate this plant have to move around a bit to find the true flowers. This mix is also one of the reasons whay the plant is in bloom for months: the big sterile flowers and their sepals don`t have to produce seeds, so they can stay for a while.
The sketch is made in ink and light washes of watercolour and red chalk for the texture.