Explore Plants

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 

Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.

rate this answer
Not Yet Rated

Friday - April 26, 2013

From: Decatur, GA
Region: Southeast
Topic: Invasive Plants, Non-Natives, Herbs/Forbs
Title: Invasiveness of Cosmos from Decatur GA
Answered by: Barbara Medford

QUESTION:

I have been searching for an answer concerning the invasive plant Cosmos. I know that Florida declares this but I have not been able to find out does Georgia? And specifically,is it only the yellow Cosmos or all Cosmos found in nurseries?

ANSWER:

The only member of the Cosmos genus, member of the Asteraceae family, in our Native Plant Database is Cosmos parviflorus (Southwest cosmos). Since the Lady Bird Johnson Wildflower Center is committed to the growth, propagation and protection of plants native not only to North America (excluding Mexico) but to the area in which it is being grown, in your case, DeKalb County, GA, this would not ordinarily be in our realm of expertise. However, we are interested in invasive plants and their control, native or not. By the way, according to this USDA Plant Profile Map on Southwest cosmos, it grows in neither Georgia nor Florida, so it seems unlikely that is the plant in question.

So, we went searching on the Internet for a cosmos that had the potential to be invasive and found Cosmos sulphureus, Yellow Cosmos, which is native to Central America. Since you noted it was considered invasive in Florida, we found this article on Cosmos sulphureus in Floridata. This warning is at the bottom of that page:

"WARNING
Before planting orange cosmos check locally to make sure that it is not invasive in your area. In places like Tennessee orange cosmos is naturalizing in "disturbed" areas but so far is not disrupting native plant communities."

Floridata has the same warning on Cosmos bipinnatus, native to Mexico. In point of fact, Cosmos has been so intensively hybridized that understanding what invasive tendencies you observe in any one cultivar or selection is difficult. Hybrids do not breed true from seed, so the seeds you purchase or the plants you buy may have none of the characteristics you may expect, including invasiveness.  

For one last check, we went to the website of the Southeast Exotic Pest Plant Control article Invasive Plants of the Southeast. Cosmos was not on that list, native or non-.

 

From the Image Gallery


Southwest cosmos
Cosmos parviflorus

Southwest cosmos
Cosmos parviflorus

Southwest cosmos
Cosmos parviflorus

More Herbs/Forbs Questions

Plant for full sun behind waterfall
March 21, 2009 - I have a 24 inch waterfall around my pool. I need to plant something behind it. I have full sun and hot Texas weather. I will be watering everyday, so what do you think would grow well in this area?
view the full question and answer

Poppies for a wedding in August from Highlands Ranch CO
February 04, 2013 - Are poppies available to buy for weddings in August in Colorado?
view the full question and answer

Salvia that needs dividing in Maryville MO
April 09, 2010 - I have some May Night salvia that is 3 years old. Last summer it split in the middle and spent a lot of the summer laid open. I'm wondering if it needs to be split or pruned in some way?
view the full question and answer

Plants that smell like chocolate from Coral Gables FL
July 12, 2012 - I am looking for plants that smell like chocolate. I live in south Florida. We are currently growing and testing Berlandiera lyrata. Do you know of other plants whose flowers smell like chocolate?
view the full question and answer

Replacement for grass under non-native weeping willow from Yorba Linda CA
April 24, 2012 - What would be a good replacement for the grass currently growing under a weeping willow? Something requiring low maintenance, the problem is with mowing over and around the roots.
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.