Ptilimnium nuttallii (DC.) Britton

Ozark Mock Bishop's Weed

© SRTurner

Family - Apiaceae

Habit - Annual forb, from fibrous roots and sometimes rhizomes.

	Base of plant, roots, rhizomes.
© SRTurner

Stems - Ascending to erect, to 70 cm, sometimes branched, glabrous.

	Stem and leaf bases.
© SRTurner

Leaves - Alternate, dissected. Leaf base sheaths only slightly inflated. Blades 3-10 cm long, pinnately 2-3 times compound, the main segments alternate or opposite along the rachis, but not whorled, the ultimate divisions threadlike and 4-60 mm long.

	Stem and leaves.
© SRTurner

	Single leaf.
© SRTurner

	Leaf. Leaflets branch from leaf rachis (arrows) more or less on one side, rather than being whorled. Ultimate threadlike leaf divisions can be very long.
© SRTurner

Inflorescence - Terminal compound umbels. Involucre of 6-15 bracts, these 4-15 mm long, mostly unbranched. Rays 15 to numerous, 1.0-3.5 cm long. Flowers mostly numerous in each umbellet, the stalks 3-8 mm long. Involucel of narrowly lanceolate bractlets.

	Inflorescence.
© SRTurner

	Inflorescence.
© SRTurner

	Involucre.
© DETenaglia

	Umbellet and involucel.
© SRTurner

	Inflorescence.
© DETenaglia

Flowers - Sepals 5, minute, narrowly triangular scales. Petals obovate, often appearing shallowly notched, but narrowed or tapered abruptly to a short, slender tip (which is usually folded back over the petal), white. Ovaries glabrous. Styles at fruiting 0.5-1.0 mm long, usually curved downward. Stamens 5, alternating with petals. Filaments white, 0.8mm long, glabrous. Anthers pinkish-rose, 0.3 mm long. Ovary inferior, 2-locular, with one ovule per locule.

	Florets.
© SRTurner

	Sepals and ovaries.
© SRTurner

Fruits - Schizocarps 1.0-1.5 mm long, with relatively broad, conspicuous, straw-colored to light yellowish brown surfaces between the lateral ribs and the commissures, the ribs similarly colored, the areas between the ribs with reddish brown oil tubes. Mericarps with 5 rounded ribs.

	Young fruits.
© SRTurner

	Fruits.
© DETenaglia

Flowering - June - August.

Habitat - Bottomland prairies, moist depressions of upland prairies and glades, streambanks, fens, swamps, ditches, roadsides, and railroads.

Origin - Native to the U.S.

Lookalikes - Other species of Ptilimnium.

Other info. - This species is easy to ID in the field because of its highly dissected leaves, umbels of white flowers, and wet habitat. It is differentiated from the other Missouri species of Ptilimnium by its involucral bracts, which are unbranched, and by its leaves, which have a one-sided (not whorled) attachment of leaflets to the main leaf rachis (see photo above). The terminal, threadlike leaf segments also tend to be quite long. The plant is intermediate in stature between P. costatum, which is taller, and P. capillaceum, which is shorter. The plant is scattered in Missouri with populations clustered near the Bootheel and also in the southwest corner of the state. Beyond Missouri its range is restricted to a few states in the south-central part of the continental U.S.

Photographs taken at the Dorris Creek Prairie Conservation Area, Barton County, MO., 7-28-00, and at Bethel Prairie, Barton County, MO., 7-4-03 (DETenaglia); also near Neelyville, Butler County, MO, 6-16-2023 (SRTurner).