Primrose Willow is an invasive, upright, annual, water plant in the evening primrose family and native to South America. Leaves are long and thin and yellow flowers appear in summer through winter. Primrose Willow grows in sandy, silty soil in water bodies, including wetlands and riparian areas, swamps, marshes, drains and channels. It will grow in up to 12 inches of water above the crown. To control it, it is best to plant it in a 5-gallon container. Do not plant in the landscape; it is invasive and has become problematic in many parts of the world including the southeastern United States. Primrose Willow can invade waterways and wetlands, forming dense colonies in slow moving and still waterways. It can out compete native plants, reduce fish habitat, increase flood risk, and limit waterway access. Primrose Willow spreads mostly by seeds. Mature plants can produce up to 2.45 million seeds per plant that are spread in moving water, wind and by birds.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Loam (Silt); Sand
Soil drainage
Frequent Standing Water | Moist | Occasionally Wet
Growth rate
Rapid
Maintenance
High
Form & Appearance
Habit / form
Erect; Spreading
Leaf color
Gold/Yellow; Green
Leaf arrangement
Alternate
Leaf shape
Lanceolate; Linear; Oblanceolate
Leaf feel
Smooth
Leaf size
> 6 inches long, 1-3 inches wide
Hairs present
No
Leaf detail
Long, thin, green, lanceolate leaves on erect red stems. Leaves are 8 inches long, 1 inch wide, with a pointed tip. Larger lower down and smaller higher up the stem. stalkless alternate on the stems.
Flower color
Gold/Yellow
Flower form
Solitary
Flower size
1-3 inches
Flower detail
Yellow flowers with 4 (or rarely 5) petals each and 4 red or green sepals. single in the junctions of upper leaves present from summer–winter.
Bloom time
Fall; Summer; Winter
Fruit color
Brown/Copper; Gold/Yellow
Fruit detail
Seed pods are 1.5 inches long and 1/3 of an inch wide, oblong to narrow-oblong, with lots of seeds in separate chambers. Seeds are dust like.