Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
Your nose is running and your eyes are itching. It’s the height of hay fever season. The goldenrod along the side of the road looks lovely but is making you feel miserable. Actually, it isn’t. It’s another much more inconspicuous plant called ragweed that is the source of your misery.
What is Ragweed?
Ragweed (Ambrosia spp.) is a genus of flowering plants that encompasses both annuals and perennials. It is a member of the large aster family. Ragweeds are native to North America, but have also been introduced to Europe and Asia where they have become invasive species.
It is the pollen of the plants that cause allergies. Each ragweed plant can produce up to a billion grains of pollen each year. Those tiny pollen grains are spread by wind. They can remain airborne for days and travel hundreds of miles. Rainfall will clear the pollen from the air until more is produced and starts riding the winds again.
The most common species in North America is A. artemisiifolia which is an annual. It spreads by both seeds and underground rhizomes. The plants grow to 30 inches in height with leaves that look like artemisia (wormwood), hence its botanical name. However, it is not related to artemisia.
Flowering is July to October. The plants set seed beginning in August. The seeds, which are rich in oils, stay on the plants during the winter providing a valuable food source for birds.
Ragweed is also a valuable plant for humans. Native Americans used it medicinally. In modern times, it has been used for soil remediation thanks to its ability to remove heavy metals such as lead from contaminated soils.
How to Get Rid of Ragweed
Sprays may not work
Herbicides containing glyphosate such as Roundup are often recommended to kill ragweed. Unfortunately, the plants are becoming immune to it so it is becoming less and less effective. If you want to try spraying, use herbicides during the spring and early summer when the plants are small and more susceptible. Always spray on days with no wind and follow the directions for application.
Pull ragweed up by hand
For small areas such as a flower bed, the easiest way to get rid of ragweed is by pulling it up by hand, getting as much of the roots and rhizomes as possible. Any roots or pieces of rhizome left behind will regrow into a new plant. This my favorite way to deal with ragweed. It’s very satisfying to rip the plants out of the ground. Always wear gloves when touching the plants. Some people can get an allergic reaction just by coming into physical contact with the plants. When your arm gets tired, remind yourself that the more plants you pull up, the fewer there will be to flower and then release those clouds of pollen.
Use a hoe to uproot ragweed
For larger areas such as a vegetable garden, a hoe can be an effective way to get rid of ragweed. While you’re out hoeing weeds, be sure to keep an eagle eye out for ragweed. The young plants are easily dislodged but larger ones may take a little more effort. If you are not able to get all of the roots or rhizomes out of the ground, they will regrow new plants. Don’t worry. Just keep hoeing the new plants each time they regrow. Eventually the roots or rhizome will die. As an incentive to keep hoeing those plants, remember that by doing so the plants aren’t able to flower and produce the dreaded allergy causing pollen.
Use a lawnmower to clear larger areas
If you have a large area to clear of ragweed, use your lawnmower to mow it down. You will need to mow every 2 – 3 weeks because mowing does nothing to remove the roots or rhizomes which can regrow new plants. But if you keep mowing regularly, eventually the roots and the rhizomes will die. One of the advantages to regular mowing is that the plants never have a chance to flower and develop pollen. So while the plants may keep regrowing, no pollen is being produced to cause allergies.
© 2020 Caren White
Caren White (author) on August 03, 2020:
You're welcome! I try to share organic methods so that we can improve our gardens without harming the environment.
Caren White (author) on August 03, 2020:
unfortunately, you are right about it growing and spreading pollen in wild areas!
Abby Slutsky from America on August 01, 2020:
Fortunately, I do not have this in my garden. However, you have given some great alternatives for removing it. Thanks for sharing.
Peggy Woods from Houston, Texas on August 01, 2020:
Your tips are good ones for getting rid of ragweed if one has them growing in a garden or yard. Those growing in wild areas alongside roads will continue to spread pollen and cause allergies for people who are susceptible.