Wild Flowers of Pittsburgh

Cuscutaceae

Dodder (Cuscuta gronovii)

A curious parasitic member of the Morning-Glory family. Dodder has no green coloring of its own because it has no chlorophyll; instead, a seedling must, within a few days of sprouting, attach itself to a suitable host plant, and begin to rob it of its sap.

There are many species of Dodder around the world, but this one is (as far as we know) the only one found in the Pittsburgh area, which makes it hard to misidentify. The stringy orange stems and the unearthly waxy flower clusters are unique. These vines were blooming along a tributary of Wexford Run in early September.

The genus Cuscuta usually makes its home in the family Convolvulaceae, the Morning-Glory Family; but it sometimes runs away from home and attempts to establish a household for itself as the family Cuscutaceae. Right now the botanical consensus seems to place it in Convolvulaceae.

Gray describes the genus and the species:

CÚSCUTA [Tourn.] L. DODDER. LOVE-VINE.

Calyx 5(rarely 4)-cleft, or of 5 sepals. Corolla globular-urn-ehaped, bellshaped, or short-tubular, the spreading border 5(rarely 4)-cleft, imbricate. Stamens with a scale-like often fringed appendage at base. Ovary 2-celled, 4-ovuled; styles distinct, or rarely united. Capsule mostly 4-seeded. Embryo spirally coiled in the rather fleshy albumen, sometimes with a few alternate scales (belonging to the plumule); germination occurring in the soil. — Leafless annual herbs, with thread-like yellowish or reddish stems, bearing a few minute scales in place of leaves; on rising from the ground becoming entirely parasitic on the bark of herbs and shrubs on which they twine, and to which they adhere by means of suckers developed on the surface in contact. Flowers small, cymose-clustered, mostly white, usually produced in summer and autumn. (Name supposed to be of Arabic derivation.)

Calyx gamosepalous; ovary and capsule pointed, the latter enveloped or capped by the marcescent corolla; flowers in loose panicled cymes.

Corolla-lobes obtuse, spreading.

C. gronòvii Willd. Stems coarse, often climbing high; corolla-lobes shorter than or equaling the deeply campanulate tube; scales copiously fringed; capsule globose, umbonate.— Wet shady places, N. S. to Man., and southw. — The commonest of our species. Very variable in size and compactness of clusters.


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