When Plants Attack—Giant Ragweed and Poison Ivy

giant ragweed 2

Think plants can only take abuse, not dish it out?  Then you’ve never encountered unrelenting ragweed allergies or a nice case of poison ivy rash.  These plants are no shrinking violets!

Giant ragweed, Ambrosia trifida, is an annual plant and a member of the Aster family.  You know, the same family that brings us the sweet and beautiful sunflower—a wonderful plant for the pollinators.  Did I mention ragweed is an annual?  From seed, it can grow to a height of 13 feet in one growing season!

All types of ragweed get a black eye from people with allergies and asthma because of the copious amounts of pollen they produce.  Ragweed is wind pollinated, not insect pollinated, which means the pollen is lightweight and readily lodges in your nose and eyes. With the increased amount of carbon in the air, not only is ragweed producing more pollen but pollinating over a longer period of time!   One good thing about ragweed, the seeds are highly nutritious for songbirds.

poison ivy

Poison ivy, Toxicodendron radicans, is a member of the cashew family (yes, cashews are edible only after going through a process to rid them of the compounds that cause rash). “Leaflets of three, leave them be” is good advice when tramping through an untamed area.  The really perplexing thing about poison ivy—people who do not have allergic reactions to poison ivy can develop the allergy as they age and people who have allergies can grow out of them!

Poison ivy roots, leaves, stems and fruits contain urushiols, the compounds behind the rash.  Urushiols are oily and viscous, making them slow to decompose, even in plants left composting several years.  And poison ivy should never ever be burned because what the stuff does to your skin can happen inside your lungs, causing death.

Surprisingly there are a couple of good things about poison ivy. The plant turns brilliant red in the fall.  If you’ve ever noticed the red vine wrapped around trees in a wooded area, it’s a good chance it is poison ivy. The other good thing about poison ivy is it serves as a food source for deer and birds.

Think what you will about plants being powder puffs—some of these “powder puffs” are combatants!

poison ivy fall color

Kathleen Cue
Horticulture Program Coordinator at Nebraska Extension

Kathleen serves as a Horticulture Program Coordinator. She educates people on making smart plant choices to reduce use of fertilizers and pesticides in their landscape which has a positive impact on air, water, soil and environmental quality, property values and people’s pocketbooks. She provides leadership and coordination of the NE Extension in Douglas-Sarpy Counties Master Gardener volunteer programs: the Master Gardener Speakers Bureau, and “Ask the Master Gardener” Consultations.


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