Ceratocephalus testiculatus (Crantz) Roth

Bur Buttercup

Ceratocephalus testiculatus plant

Family - Ranunculaceae

Habit - Annual forb, stemless.

Ceratocephalus_testiculatus_habit.jpgScapose habit.

Ceratocephalus_testiculatus_habit2.jpg

Stems - Absent.

Leaves - All in basal rosette, 0.9-3.8 cm long, 0.5-1.5 cm wide, 1-2 times dissected, broadly spatulate in outline, the ultimate segments linear, entire, blunt pointed at the tip, the surfaces sparsely to densely and finely woolly.

Ceratocephalus_testiculatus_leaves1.jpgLeaves adaxial.

Ceratocephalus_testiculatus_leaves2.jpgLeaves abaxial.

Inflorescences - Solitary flowers on long, hairy stalks.

Flower - Actinomorphic, perfect, the stalk 3-7 cm long, sparsely to densely and finely woolly. Sepals 5, 3-6 mm long, 1-2 mm wide, green, sometimes almost hidden in the dense white woolly hairs, persistent at fruiting. Petals 5, 3-5 mm long, 1-3 mm wide, yellow. Stamens not showy, the anthers yellow. Pistils 20-50, each with 1 ovule. Style present, persistent.

Ceratocephalus_testiculatus_flower.jpgFlower.

Fruit - Ellipsoid achenes clustered in cylindrical heads, these 9-16 mm long and 8-10 mm wide; the main body of each fruit 1.6-2.0 mm long, 1.8-2.0 mm wide, the fruit wall thick, not veined, woolly-hairy, the beak 3.5-4.5 mm long, lanceolate. Receptacle becoming elongated and cylindrical in fruit, glabrous.

Ceratocephalus_testiculatus_fruit.jpgFlower and fruit.

Flowering - March - May.

Habitat - Lawns or other disturbed areas, picnic areas, campgrounds.

Origin - Native to Eurasia.

Lookalikes - None close.

Other info. - This small but easily identified species is uncommon in Missouri, currently reported from only seven counties. It is far more common east of the Rocky Mountains. Its abundance in Missouri appears to be slowly increasing. Botanical references describe the flowers as being five petaled, but it is common to see flowers with fewer petals. The plant is found in highly disturbed areas, where it tends to form dense mats. It is considered invasive in some western areas of the country.

The genus name Ceratocephalus means "horned head," referring to the fruiting heads of pointed achenes. Other names used for the plant have included Ceratocephala testiculata and Ranunculus testiculatus.

Photographs taken at Kirkwood City Park, St. Louis County, MO, 4-2-2019 (SRTurner).



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