How much sun does Horseweed need?

Horseweed grows best in full sun conditions.

When does Horseweed bloom?

Horseweed blooms in July, August, and September.

Where is Horseweed native?

Horseweed (Ambrosia trifida) is native to AL, AR, AZ, CO and 42 more states, per the World Checklist of Vascular Plants (Kew).

What pollinators does Horseweed attract?

Horseweed draws bees, beetles, and flies.

Is Horseweed HOA-friendly?

Horseweed takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

Horseweed

Name: Pollinator Patch
Author: Pollinator Patch

Ambrosia trifida

Last reviewed: August 2026

Toxicity unknown

Horseweed (Ambrosia trifida) 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

low

Size

12"–60" H × 6"–24" W

Bloom

Jul, Aug, Sep

Native to

AL, AR, AZ, CO and 42 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 452 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 Mountains Southern Rockies Arizona/New Mexico Mountains High Plains Southwestern Tablelands Central Great Plains Great Plains Cross Timbers Edwards Plateau Texas Blackland Prairies East Central Texas Plains Western Gulf Coastal Plain South Central Plains Eastern Temperate Forests Ozark Highlands Central Irregular Plains Northwestern Glaciated Plains Northwestern Great Plains Piedmont Northern Glaciated Plains Western Corn Belt Plains Northern Lakes and Forests North Central Hardwood Forests Driftless Area Southeastern Wisconsin Till Plains Central Corn Belt Plains Eastern Corn Belt Plains Southern Michigan/Northern Indiana Drift Plains Huron/Erie Lake Plains Northeastern Highlands Northeastern Coastal Zone Northern Allegheny Plateau Erie Drift Plain Northern Forests Middle Atlantic Coastal Plain Northern Piedmont Southeastern Plains Blue Ridge Ridge and Valley Central Appalachians Western Allegheny Plateau Interior Plateau Interior River Valleys and Hills Mississippi Alluvial Plain Mississippi Valley Loess Plains Southern Coastal Plain Madrean Archipelago Sonoran Basin and Range Eastern Great Lakes Lowlands Atlantic Coastal Pine Barrens

Giant ragweed is a tall annual wildflower that can reach up to 5 feet in height with distinctive three-lobed leaves. It produces small greenish flowers in late summer and is well-adapted to disturbed soils and full sun conditions. This native plant self-seeds readily and can form large colonies in suitable locations.

In an HOA neighborhood

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

Works well in: backyard only.

Aggressive self-seeding can appear weedy
Very tall growth may violate height restrictions
Common ragweed appearance triggers allergy concerns

Wildlife value

The flowers attract bees, beetles, and flies during late summer blooming period. Seeds provide food for birds, particularly finches and sparrows in fall.

Common questions

How much sun does Horseweed need?: Horseweed grows best in full sun conditions.
When does Horseweed bloom?: Horseweed blooms in July, August, and September.
Where is Horseweed native?: Horseweed (Ambrosia trifida) is native to AL, AR, AZ, CO and 42 more states, per the World Checklist of Vascular Plants (Kew).
What pollinators does Horseweed attract?: Horseweed draws bees, beetles, and flies.
Is Horseweed HOA-friendly?: Horseweed 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.

If something looks wrong

Common plant problems, and what to check first

These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.

See all plant problem guides

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