Oenothera biennis 

Common Evening Primrose 

Biennial 

• Full sun to light shade
• Average to very well drained soils (including roadside gravel)
• height varies with first year success, anywhere from 2' tall to over 7'. 12" to 36" wide. Generally fairly narrow but can become branched and bushy if topped as they are developing their blooming stem.
• New gardens and disturbed areas. 
• Flowers, immature seed pods, young foliage and tap root (before blooming) are all edible.

Like a lot of biennial species, Common Evening Primrose has a lifecycle affinity for disturbance and is prolific in both flowering and seeding.

They are quick to make themselves at home in physically disturbed soil and on gravely roadsides, where their taproot will both anchor them and allow them to reach down for moisture.

In rich garden soil those taproots can become quite robust, enough that they can be grown as a native root crop if you harvest them at the end of their first growing season. Their seeds and young seed pods are also edible.

Their first-year foliage is a ground-hugging rosette that can come in a range of sizes. In the second year they reach upwards into a tall, narrow stalk that, in a garden or meadow setting can either be a single stem all the way or with some smaller side branches.

In roadside settings I’ve also seen them a strongly branched, bushy form. I’m not sure if this is because they have plenty of space and little competition in some spots, or if it is a result of having the central stem mowed and they responded by developing lots of branches instead.

As a true biennial, these will spend all of their energy maturing the, often, 1000s of oil rich seeds and then fade. This doesn’t mark the end of their aesthetic presence in the garden though. Their stems and seed pods are very sturdy and will hold up well into the winter, often still standing tall the following spring.

I generally see these thriving in hot, sunny locations, where they seem to be entirely unbothered by dry spells, but the one pictured in today’s photos was shaded from about 2pm onward. Their size is mostly defined by how much energy they are able to gather in their first year, but don’t be surprised to see them extend to over 6’ in height if they are particularly pleased with their setting.