evening-primroses (Oenothera) — identification, habitat & look-alikes

Evening-primroses are a group of flowering plants native to the Americas, with species growing in fields, prairies, deserts, and coastal dunes across much of the United States. The flowers can be yellow, white, or pink, and some species have flowers open in daylight. Four petals and a pollen-receiving tip split into four arms like a cross help identify the group.

In this group

common evening-primroseOenothera biennis

Common in eastern and central fields and roadsides, it sends up a tall spike of yellow flowers that usually open near dusk.

pinkladiesOenothera speciosa

Native to the central and southern United States, it makes spreading patches of large white-to-pink flowers that are often open by day.

meadow evening primroseOenothera pilosella

An eastern North American perennial, it has upright yellow flowers and a more meadow-like habit than the tall common evening-primrose.

clockweedOenothera lindheimeri

Native to Texas and Louisiana and widely grown, it has airy wands of white or pink flowers with long pollen-bearing stalks.

cutleaf evening primroseOenothera laciniata

This low, branching plant grows on sandy or disturbed ground and has small yellow flowers and irregularly cut leaves.

rose evening primroseOenothera rosea

A low plant with small rose-pink flowers, it is native from the southwestern United States southward and is introduced elsewhere.

Appearance

Growth form: The genus includes annual, , and perennial herbs. Plants range from low mats to upright stems several feet tall.
Flowers: Flowers may be yellow, white, or pink. Common evening-primrose often opens near dusk, while pinkladies may stay open in daylight, so bloom time alone does not define the genus.
Fruit: The part just below the petals develops into a dry with many seeds.
How to recognize it: Look for four broad petals, eight slender stalks bearing pollen, and a that splits into four arms like a small cross. Leaves grow alternately along the stem, and many species begin as a ground-level .

Look-alikes

primrose-willowsLudwigia

Some have four yellow petals too. Primrose-willows often grow in wet places and have a rounded or only shallowly lobed stigma; Oenothera has four long stigma arms.

Why they get mixed upThe yellow four-petaled flowers can look similar.

Where it lives

Typical habitats: prairies and open woods
roadsides and fields
sand dunes
gardens
Range: Oenothera is native to the New World, with species across much of the United States. Different species belong to eastern fields, Great Plains prairies, western deserts, coastal dunes, and gardens.
Preferred conditions: Many species favor sunny, open ground and well-drained soil, but moisture needs differ widely.

Life cycle

Seed dispersal: Ripe capsules split and release small seeds. Some perennial species also spread by underground stems or roots.

Growing it

Care: Pinkladies, bigfruit evening-primrose, sundrops, and clockweed are grown in U.S. gardens. Some spread strongly by roots or seed and can move beyond the bed.

Name and classification

About the name: Several plants once placed in Gaura are now included in Oenothera. Clockweed (Oenothera lindheimeri) was formerly called Gaura lindheimeri.
Group name: Evening-primroses is a name for the genus. U.S. field guides also use sundrops, suncups, and beeblossoms for some of its species; true primroses (Primula) belong to a different genus.
Number of species: The genus has 156 recognized species worldwide.

Culture and stories

Culture and stories: The name evening-primrose refers to the dusk-opening flowers of some species.

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