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Giant Sumpweed

Cyclachaena xanthiifolia

Last reviewed: August 2026

Giant Sumpweed (Cyclachaena xanthiifolia)
Photo: Serobacterium / Wikimedia Commons (CC BY-SA 3.0)

Toxicity unknown

Giant Sumpweed (Cyclachaena xanthiifolia) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.

Light

full sun

Water

medium

Size

24"–60" H × 12"–24" W

Bloom

Jul, Aug, Sep

Native to

AL, AZ, CA, CO and 38 more states

Pollinators

bees, beetles, flies

Before you buy

Your city may pay you to plant this

Cities and water utilities offer rebates for replacing lawn with native and water-wise plants. We track 445 programs across 44 states, each with a link to the provider and the date we last checked it.

Find rebates in your area

Browse plants for this ecoregion

Northwestern Forested MountainsNorth American DesertsCentral Basin and RangeSouthern RockiesArizona/New Mexico MountainsHigh PlainsSouthwestern TablelandsCentral Great PlainsCentral Irregular PlainsNorthwestern Glaciated PlainsNorthwestern Great PlainsGreat PlainsNorthern Glaciated PlainsWestern Corn Belt PlainsNorthern Lakes and ForestsNorth Central Hardwood ForestsDriftless AreaSoutheastern Wisconsin Till PlainsCentral Corn Belt PlainsEastern Corn Belt PlainsNortheastern HighlandsNortheastern Coastal ZoneRidge and ValleyInterior River Valleys and HillsEastern Great Lakes Lowlands

Giant ragweed is a tall, fast-growing annual wildflower with large, deeply lobed leaves that can reach 5 feet in height. It produces small, inconspicuous greenish flowers from July through September and thrives in sunny locations with average moisture. This native plant self-seeds readily and can form substantial colonies in favorable conditions.

In an HOA neighborhood

Giant Sumpweed takes more care to keep looking intentional in a front yard. Maintenance level: low. Consider it for backyard or mid-zone beds rather than the street edge.

Works well in: backyard only.

  • Very tall and can appear weedy
  • Aggressive self-seeding habit
  • May trigger allergies in sensitive individuals

Wildlife value

The flowers attract various pollinators including native bees, beetles, and flies during its long summer blooming period. Seeds provide food for birds, particularly finches and other seed-eating species in fall.

Common questions

How much sun does Giant Sumpweed need?
Giant Sumpweed grows best in full sun conditions.
When does Giant Sumpweed bloom?
Giant Sumpweed blooms in July, August, and September.
Where is Giant Sumpweed native?
Giant Sumpweed (Cyclachaena xanthiifolia) is native to AL, AZ, CA, CO and 38 more states, per the World Checklist of Vascular Plants (Kew).
What pollinators does Giant Sumpweed attract?
Giant Sumpweed draws bees, beetles, and flies.
Is Giant Sumpweed HOA-friendly?
Giant Sumpweed takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

Native range data from the World Checklist of Vascular Plants (Kew). Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.

Ready to grow Giant Sumpweed? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.

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