An invasive vine that has really taken off in this park by the water. This image shows several plants, most notably the orange flowers, which are not my subject here - that is Spotted Jewelweed / Touch-me-not / Impatiens biflora. My subject here is the vining plant with stacks of blue berries and triangular leaves. Too mixed up to get just one of the plants as my focus!
The plant is in the stage of mostly green berries, with some turning blue and pink and purple.
This plant was formerly known as Polygonum perfoliatum.
Belle Haven Park next to the Potomac River
The orange flowers are Jewelweed.