This plant is trailing along a rocky beach just out of reach of the high tide, climbing amongst driftwood, a feral Malus tree, and Rubus armeniacus. It gets nearly full sun except some intermittent shade from the Malus. The leaves have a cordate base and a general heart shape with an acuminate blade tip; they range in size from 3 to 8 inches long; leaf margins are entire but relatively sinuose. Entire plant glabrous. Flowers white, bisexual, actinomorphic, gamopetalous, and 5-merous; the majority have an approximately 3 inch diameter.
It stands out from the native C. sepium because of its overlapping bracteoles. But it may be a hybrid or other species.
No flowers or fruits, but I can't think what else these leaves could belong to. I'm only familiar with the low-elevation var. palmatus.
Calyx 7mm, moderately pubescent on outer surface, Corolla tube 12mm
In roadside scree.
Common, smaller and thinner leaved than Isoetes occidentalis here
Could there be V. scopariun on the Peninsula? It looks unlike the V. parvifolium that has new, big, bright green leaves.
@geographerdave did I get it right this time?