Smartweed Dodder (Cuscuta obtusiflora)
Description
This herbaceous vine is a summer annual up to several feet long that branches occasionally to abundantly. It sprawls across other vegetation that it parasitizes, extracting water and nutrients through clinging suckers (haustoria). Sometimes this vine is so robust that it forms a dense maze of stems that partially obscures the vegetation underneath. The stems are orange, terete, glabrous, and occasionally warty. The alternate leaves are reduced to minute scales or they are absent. Small clusters of flowers develop at intervals along the stems on greenish yellow peduncles and pedicels that are glabrous. The pedicels of the flowers are very short (less than 1 mm. in length). Each flower spans about 3 mm. across, consisting of a short-tubular calyx with 4 obtuse lobes, a short-tubular corolla with 4 ascending to erect lobes, 4 stamens, and a pistil with a pair of divergent styles. Less commonly, a flower may have 5 calyx lobes, 5 corolla lobes, and 5 stamens. The calyx is light green or pale yellow and glabrous, while the corolla is white and its lobes are ovate with blunt tips. The lobes of the calyx extend to about the sinuses of the corolla or a little less. Inside the corolla at the base of the stamens, there are fringed floral scales (requires at least a 10x hand lens to see). The blooming period occurs from mid-summer to early fall, lasting about 1- months. The flowers may be slightly fragrant, and they are self-fertile. The flowers are replaced by globoid seed capsules spanning 3-5 mm. across; they are surrounded by their persistent calyces and the withered remnants of their corollas. Immature seed capsules are light green or pale yellowish green, but they become brown at maturity. Each capsule has 2 cells and contains up to 2 seeds per cell. The seeds are 1.0-1.5 mm. in length and ovoid in shape. While a young seedling has a rudimentary root system, it soon withers away after the seedling attaches itself to a suitable host plant. Without a host plant, the seedling soon dies as it lacks chlorophyll.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Magnoliophyta
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Class: Magnoliopsida
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Order: Solanales
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Family: Convolvulaceae
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Genus: Cuscuta
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