Wood Spurge (Euphorbia amygdaloides) grows, not surprising, in woods and it starts flowering long before the tree leaves start growing.
Spurges, at least those growing in France, have some characteristics in common. If you break a stem or leaf, a white latex oozes. And most Sprurges have typical yellow-greenish flowering umbels.
Wood Spurge is not an exception.
Here a 'flower' in detail. Round petal-like structures form a kind of saucer under some unusual machinery. Those two green-yellow half-circles are not petals, Wood Spurge does not have them, but bracts. And the little red ball inside is a not yet ripe fruit. It carries still the rests of pistils, two green lines. Left and right of this fruit, under two half-moon shapes, new flowers begin to open. And those half-moons? They are nectariferous glands. On top of all of this there are some stamen with pollen.
The rather blue-green leaves sometimes tinged with red look like they belong to another species.
And when, at least, the trees start making new leaves, Wood Spurge does not stop immediately making flowers.