Oenothera villosa
(Hairy Evening-primrose)
Onograceae
Oenothera villosa is a showy, native that likes moist open meadows in forests and disturbed areas. Being a primrose (of path fame) it starts to flower just as the sun is going down.
Flowers
O. villosa is biennial. It doesn't flower at all during its first year - it's just a ring of leaves on the ground. The second year it blooms during early and mid summer. And only when it's dark. Even then, only a few flowers bloom at a time.
The plant doesn't have very many flowers. They're arranged in a spike with each flower at the end of a short stem.
They have 4 bright yellow petals that often overlap.
The petals are broadly heart-shaped, with a distinct notch separating two rounded lobes. They can be up to 15 or 20 mm long.
The calyx under the corolla has sepals that are almost as long as the petals and are sometimes tinged with red.
O. villosa has 8 long stamens and a shorter pistil that is divided into 4 parts.
As the flowers mature, they usually fade to orange or red.
Leaves
There are basal leaves and leaves alternating up the stem. They're lance-shaped but can be wider at the top than at the base. They sometimes have small, well-spaced teeth around the margin.
The stem leaves are larger low on the plant and get smaller higher up,
Stem
The stems can be 2m tall. They're erect and sometimes branch near the bottom. They're hairy and the hairs have red glands at the base.
Fruit
The long hypanthium eventually becomes a long fruit.
The fruits are distinctive, cylindrical capsules that stick up from the leaf axils. They're about 25-30 mm long and 5 mm wide.
As they mature, they split apart lengthwise to release the seeds. The seeds are a couple of mm long, angled and pitted.
Range & Habitat
O. villosa grows in about half of Colorado's counties. but those counties are distributed randomly. Nationally, it's in all of the northern and western states.
It's comfortable in open forest meadows as long as there's enough moisture. It also colonizes disturbed areas.
