Calylophus serrulatus (Yellow Sundrops)

Plant Info
Also known as: Toothed Evening Primrose, Plains Yellow Primrose
Family:Onagraceae (Evening Primrose)
Life cycle:perennial
Habitat:sun; dry prairies
Bloom season:June - August
Plant height:1 to 2 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 4-petals

[photo of flower] Single yellow flowers in the upper leaf axils, ½ to 1 inch across, with 4 rounded petals, often quite wrinkled like crumpled tissue paper, with wavy edges that are sometimes a bit ragged, and a rounded notch at the tip. In the center are 8 yellow stamens surrounding a stigma with 4 disc-shaped lobes. The 4 sepals are less than ¼ inch long, triangular to egg-shaped with a prominent mid-rib, and reflexed down at bloom time. Flowers are stalkless but sit on top of a hairy, cylindrical ovary about 3/8 inch long that resembles a stalk.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves] Leaves are narrowly oblong, linear, or widest above the middle, 1 to 3 inches long and not more than ¼ inch wide, stalkless, may be toothless but usually with small, sharp teeth around the edges and short hairy on the underside. Stems are erect, green to brown, covered in stiff, fine hairs, often clustered from a root crown but not much branched, and woody in the lower stem.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is a slender, cylindrical capsule in the leaf axils, slightly tapered at both ends, ½ to 1¼ inches long, covered with fine, short hairs.


At first glance, Calylophus serrulatus looks like an Oenothera and not surprisingly, at one time it was known as Oenothera serrulata. Common in dry prairies, it is typically much shorter than the tall spiked stems of other common evening primroses and has much narrower leaves. A distinction with this species is that it blooms during the day where Oenothera flowers open in afternoon or evening, for pollination by night-flying insects.

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More photos

Photos by K. Chayka taken at Long Lake Regional Park, Ramsey County, and at Grey Cloud Dunes SNA, Washington County. Photos courtesy Peter M. Dziuk taken in Dakota and Pope counties.


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Nancy - Dakota and Goodhue Counties
on: 2013-08-01 10:13:50

I see this plant in remnant sand prairies and have found it in several locations. A beautiful but somewhat inconspicuous member of our native prairie flora!

Posted by: Elizabeth
on: 2018-07-16 09:10:27

Can anyone identify the purple/blue flower in photo 6 of 8 above? I would love to grow them together, what a nice combination.

Posted by: K. Chayka
on: 2018-07-18 19:03:19

Verbena stricta, hoary vervain.

Posted by: Brett - Clay County
on: 2019-07-18 17:57:27

First time seeing this plant...In Blanket Flower SNA.

Posted by: Timothy Johnson - Hennepin County
on: 2022-06-29 10:48:03

These are doing well in a restored dry sandy prairie in Oxbow Park, Champlin, MN

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