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Giant Sumpweed, Marsh-elder (Cyclachaena xanthiifolia, Iva xanthiifolia), fam. Asteraceae.
A weed, growing sometimes along the road. Its leaves and inflorescences are similar to Lambsquarters, but much larger. Wide and big leaves of some sumpweed plants also remind Cocklebur (Xanthium). The latter is a closer relative of Giant Sumpweed, from the same daisy family, and a worhty rival in sturdiness.
The species originates from North America prairies. In the 1870s giant sumpweed had been planted in Kyiv botanical garden, after that in the 1920s it has spread along Ukraine and then Russia. It blooms in July-October, the seeds ripen in August-October. Its pollen may cause allergy, like that of Common Ragweed. The plant is not eaten by animals (poisonous), and strongly depletes the soil. The shoots and leaves of the weed contain the substances which are toxic to other plants (inhibitors). After sumpweed death, other plants cannot grow in the same place for some time.