In Defense of Giant Ragweed

Sep 4, 2014 - 8:01 am

Yes, ragweed plants grow tall, really tall. It may seem overwhelming to even approach an area covered with ragweed, let alone venturing through it. Some people sneeze during the whole ragweed pollination season and some have allergic reactions when their skin touches the stalks. Knowing this and confronted with a wall of ragweed, what is the first thing that comes to mind? Get rid of it!!!

Well, hold on, slow down. Could there be something positive about this plant? Would you be willing to pause a little, control the impulse to mow it all down?? There are some significant benefits provided by ragweed, benefits that are worth giving some thought before you just get rid of the green giant.

A Plead FOR Ragweed

Native tree growing under radweedRagweed provides shade against the baking sun during the summer months, cooling down the soil. The much needed shade protects the soil from drying out fast after it rains and helps keep moisture in the soil longer. So, although it looks like ragweed is overtaking an area and not letting anything else grow, it is actually creating a more hospitable plant habitat than areas exposed to full sun. Tree seedlings under ragweed are sheltered during the most hostile months of the year and have a better shot at surviving. Because ragweed is an annual species, and is mostly gone after setting seed in the fall, it allows a window of light for tree seedlings and other cool season plants to grow while the temperatures are not too high. If you dare to venture into a ragweed jungle, and look around carefully, you will be surprised that it is not only ragweed. Here and there you may find a few tree seedlings, probably hackberries and cedar elms, braving their way into the world.

Ragweed has a taproot that penetrates the soil, and helps reduce soil compaction.  Loose soil allows water to infiltrate to the plant roots rather than runoff.  After the plant dies, the root system also adds organic carbon to the soil and the aboveground plant serves as mulch. Over time, areas with ragweed will develop better soils than areas that are constantly mowed. Furthermore, during storm events, leaves and soil that are carried in the runoff get hung up and caught by the ragweed stems, cleaning the water and building healthier streamside soils.

 

Ragweed is a pioneer, a true survivor, one of the few plants that can colonize a site that has been mistreated by human action. It grows so fast that it can even outgrow Johnson grass and help control it. But, even such a champion cannot win forever. Pioneer plants have a limited future, since they create better conditions and other plants will eventually outcompete them. Seedlings using ragweed as a nursery will grow and cast shade. Ragweed does not grow as vigorously in shaded areas. Over time, it will no longer be the dominant towering presence you see now, just another plant in the community or a fading memory.

Ragweed trapping debris.Ragweed holding streambank

 

Managing ragweed.All right, that means years, and lots of patience. Yes, ragweed is not going away anytime soon and perhaps you are still committed to fight ragweed.  You can seed native grass and wildflower to add some competitors for ragweed. If the area covered by ragweed is not too big, you may try thinning it early in the spring when the plants are still small and pulling them will not create much soil disturbance. However, you may need to pull seedlings more than once because not all seeds germinate at the same time. Make sure you target only ragweed and give the native plants you seeded a better chance.

If all you need is a bit more visibility, ragweed can be cut at three feet to maintain some shade but allow a view of the area. Late in the summer, once it has started flowering, ragweed can also be bent over or cut at the base and it will prevent resprouting and reduce the number of seeds produced. Lay the cut plants in appropriate areas so it still provides the green mulch-effect.

But, if you have the patience to wait and see, you can witness how a forest starts from scratch, down at the creekside.

Click here to be notified about volunteer workdays to help manage ragweed.

For more information, please contact Ana Gonzalez  or 512-974-2929

Share