Euphorbia palustris has proven to be an early spring winner in my wet clay environment. Most plants that like my conditions get off to a slow start and come into their own much later in the season, in July to August. But this water lover is a real early season gem. I think I should develop a list of golden plants for this early season. They really brighten the view of my perennial plantings, most of which are just emerging from the ground as a kind of rough stubble.
The largest Euphorbias are about 30 inches tall. I have two planted with the variegated Calamagrostis 'Overdam', a combination that works well.
This plant is in its second full year. Lots of sun seems to be to its liking. Two planted in the shade have hardly grown at all.