This section is from the book "Who's Who Among The Wild Flowers", by W. I. Beecroft. Also available from Amazon: A Field Guide to Edible Wild Plants.
Common Sundrops:
Oenothera fruticosa. Evening Primrose Family. May - July.
Plant 1 - 3 feet tall, found in fields, roadsides. New England to South Carolina, west to Indiana and Michigan.
Yellow, 1/2 - 1 inch across, 4 divisions, terminating stem and from the leaf angles. Seed pods ribbed and winged.
Oblong to lance-shaped, minutely toothed. 0. pumila is a similar but smaller species. Leaves toothless, basal leaves broader at the tip. More western in its range.

Sundrops.
 
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