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Cuman ragweed is a cousin of common ragweed and both are notable as the culprits in many cases of hay fever. Cuman ragweed’s vast range across North America matches the range of common ragweed except for the Far North. No escape for people with allergies.
Cuman ragweed (or Western ragweed depending on who’s talking), is a gangly plant with lobed leaves and upright stems that end in one or more narrow flower stalks, laddered with thirty or more flower clusters. Each cluster bears half a dozen flowers. This adds up. Six stems, thirty clusters, six flowers per cluster--the total for one plant is a lot of pollen and red noses. (One mitigating fact: some birds eat the seeds.)
Western ragweed is a perennial where climate permits and an annual almost everywhere. A strong plant can reach 3.5 feet tall in one season. It is an opportunist (or, less politely, a weed), popping up unaided in waste ground and disturbed soil at the edge of a garden, cornfield or country road. It is everybody’s neighbor.
Phenology is the science of recording events in the life cycle of plants and animals. National Phenology Network (USA-NPN), an organization that is building a phenology database with help from thousands of volunteers, maintains a web site with information about “Calibration” species (Cuman ragweed is one), chosen because the plants are widespread.
The events for Cuman ragweed include first green in spring, first full-size leaf, first flower, first fruit and first withered leaf in fall. Such observations tell us about our changing climate, why our noses are running, and which plants, whether trees, shrubs or ragweed, have similar phenology.
Someday, thanks to USA-NPN and volunteer Citizen Scientists, we gardeners will time our sowing, pruning, and other seasonal chores when forsythia blooms, ragweed sprouts, oaks have leaves the size of a squirrel’s ear, or when we start sneezing.
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