Calylophus serrulatus (Yellow Sundrops)
Also known as: | Toothed Evening Primrose, Plains Yellow Primrose |
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Genus: | Calylophus |
Family: | Onagraceae (Evening Primrose) |
Life cycle: | perennial |
Origin: | native |
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): | ![]() |
National distribution (click map to enlarge): | ![]() |
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Detailed Information
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:
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 is a slender, cylindrical capsule in the leaf axils, slightly tapered at both ends, ½ to 1¼ inches long, covered with fine, short hairs.
Notes:
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
Yellow Sundrops plants
Yellow Sundrops plants in the grass
Yellow Sundrops habitat
wrinkled flower petals
more flowers
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.
Comments
Have you seen this plant in Minnesota, or have any other comments about it?
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!
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.
on: 2018-07-18 19:03:19
Verbena stricta, hoary vervain.
on: 2019-07-18 17:57:27
First time seeing this plant...In Blanket Flower SNA.
on: 2022-06-29 10:48:03
These are doing well in a restored dry sandy prairie in Oxbow Park, Champlin, MN