I bought some lovely beach plum jam last summer. While enjoying it I thought, "It would be nice to make my own beach plum jam. I'll have to remember to look for the plum blossoms in the spring, so I know where to find beach plums." I spotted the telltale white blossoms along Long Beach this weekend.
There are clumps of white blossoms.
Look here for a beach plum harvest.
Beach Plum prunus maritima
Beach plum jam recipe by Justine Hand at Gardenista here