Giant ragweed (Ambrosia trifida)

Giant ragweed

Also known as: Horseweed, Great ragweed

Giant ragweed, a native plant to North America, is an allergy sufferer's nightmare. It causes dramatic allergic reactions in more than 23 million Americans annually. In spite of this, the wildflower is edible, and evidence suggests that Native Americans actually planted it as a crop and harvested the seeds for their oil. Giant ragweed can be invasive, however, and out-competes many native species. Modern horticulture practices recommend against planting it.

Scientific classification

Species

Giant ragweed (Ambrosia trifida)

Asters bellflowers fanflowers and allies

Instantly identify plants with a snap

Snap a photo for instant plant ID, gaining quick insights on disease prevention, treatment, toxicity, care, uses, and symbolism, etc.

Download the App for Free

Weeds

Weed or not

2 m

Plant Height

1.5 m

Spread

Green, Blue

Leaf Color

5 mm

Flower Size

Brown

Fruit Color

Yellow, Green

Flower Color

Green

Stem Color

Winter dormancy

Dormancy

Deciduous

Leaf type

20 - 38 ℃

Ideal Temperature

Images of Giant ragweed

Distribution of Giant ragweed

Distribution Map

Giant ragweed is native across North America. Its native habitat includes woodland edges and disturbed prairies, meadows, and roadsides. It has been introduced in western Europe, the Mediterranean, and eastern Asia. Giant ragweed is considered an invasive agricultural weed in most locations where it grows.

Native

Cultivated

Invasive

Introduced

No species reported

Discover plant distribution and habitat

Gain insights into where plants thrive and how they adapt, helping you identify, cultivate, and protect them with essential information on habitats, distribution maps, and climate trends.

Download the App for Free

Habitat

Alluvial waste places

Hemisphere Trend Curve

Northern

Sorthern

Culture

Symbolism

Courage, fertility

Interesting Facts

Many have tried to stop the spread of this invasive weed, giant ragweed, because its pollen causes significant allergic reactions. However, Native Americans used giant ragweed as medicine for problems such as fever, pneumonia, diarrhea, and insect stings. It can be used in sheet mulch gardens and compost.

Name Story

Giant ragweed: Ragweed is the common name for any of the species that are wind-pollinated. Its pollen and seeds can be dispersed by wind everywhere and this plant can typically grow up to 2 meters in height. In some fertile soil, the plant can grow up to . Hence it is called giant ragweed.

Get quick plant knowledge with a snap

Snap a photo for instant plant identification and learn about its name, symbolism, interesting facts, uses, and more.

Download the App for Free

Toxicity

Giant ragweed pollen causes hay fever in humans but is not life-threatening. Giant ragweed is toxic to cats and dogs. When ingested by pets, it can lead to poisoning; symptoms in cats include discomfort, in dogs, gastrointestinal upset and skin irritation. Immediate veterinary care is needed for both if giant ragweed poisoning is suspected. Giant ragweed grows in sunny, rich soil areas globally.

Identify toxic plants in your garden

Find out what’s toxic and what’s safe for humans and pets.

Download the App for Free

Weed Control

Native to North America, giant ragweed is commonly known for being a common cause of hayfever. It can be found across the USA, Canada, Europe, and Asia, and is noted as a noxious weed in several US states and northeastern China. Giant ragweed produces copious amounts of allergenic pollen, and a single plant can produce up to 10,300 seeds. This makes it extremely competitive with other species, and it has even been known to reduce crop yields by 50% or more. It is destructive to native plants and crops also due to its high competition for light.

How to Control It

The best season to remove giant ragweed is spring. It's important to remove it before it reaches a height of over 12 inches for more efficient control. This usually happens in the later part of June or at the beginning of July.

Hand-pulling: This is the simplest method. Ensure you have gloves, a long-sleeved shirt, and long pants to minimize exposure to the plant. Grasp the plant at the base and pull upward to remove the whole plant from the soil. Dispose of the plant immediately in a sealed bag.
Mowing: This method is effective when the plants are young and not too large in number. Mow the area where giant ragweed is growing frequently to prevent it from developing seeds. Remember always to clean the mower afterward to avoid spreading the weed to other areas.
Hoeing: This method works best when the soil is dry. Use a garden hoe to slice off the weed at the ground level. Be careful not to disturb the soil too much, as this can bring more weed seeds to the surface.

Identify toxic plants in your garden

Find out what’s toxic and what’s safe for humans and pets.

Download the App for Free

Care Guide for Giant ragweed

Every week

Water

Full sun

Sunlight

20 - 38 ℃

Ideal Temperature

Water: Giant ragweed thrives in moderate moisture, requiring weekly watering to sustain optimal growth. Native to rain-rich areas, it is not drought-tolerant. As an annual herbaceous plant, giant ragweed has a specialized growth cycle to effectively utilize available water during its growing season.

Propagation: Giant ragweed is easily propagated by sowing seeds in Spring, with successful germination shown by emerging seedlings. No further propagation tips are necessary.

Get tips and tricks for your plants.

Keep your plants happy and healthy with our guide to watering, lighting, feeding and more.

Download the App for Free

Images of Giant ragweed

Distribution of Giant ragweed

Culture

Toxicity

Weed Control

Care Guide for Giant ragweed

PEOPLE ALSO ASK