Host an Event Volunteer Join Tickets

Support the plant database you love!

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

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
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
Not Yet Rated

Saturday - March 30, 2013

From: Houma, LA
Region: Southeast
Topic: Invasive Plants, Non-Natives, Planting, Herbs/Forbs, Trees
Title: Planting petunias around base of oak tree from Houma LA
Answered by: Barbara Medford

QUESTION:

I live in south Louisiana and I want to plant petunias. Can I plant petunias around the base of an oak tree?

ANSWER:

There are 8 members of the genus Ruellia (wild petunia) native to North America, of which Ruellia caroliniensis (Carolina wild petunia) and Ruellia nudiflora (Violet ruellia) are native to in and near Terrebonne Parish in the southeastern portion of Louisiana. If you follow the plant links to our webpage on each plant you will learn that both like moist soil and can tolerate some shade. That would mean they could grow under an oak tree. BUT, you need to read this previous Mr. Smarty Plants answer about allelopathy in oaks and Ruellia brittoniana, which is the non-native Mexican petunia. Also see this Florida article about Ruellia or Mexican Petunia and note the warnings about its invasiveness.

Now, lets talk about the other petunia. Pelargonium (petunia) is a genus of 35 species of flowering plants of South American origin, closely related to tobacco, cape gooseberries, tomatoes, deadly nightshades, potatoes and chili peppers; in the family Solanaceae. From Google, here are pictures of the "other" petunia.

Frankly, we don't think either the native or non-native petunias would prosper under your oak tree, and the non-native members of the Solanaceae famly apparently need full sun, which we consider to be 6 hours or more of sun a day.

 

From the Image Gallery


Carolina wild petunia
Ruellia caroliniensis

Violet ruellia
Ruellia nudiflora

More Planting Questions

Would like fast growing evergreen trees in Austin, TX.
October 31, 2012 - Hi, We're moving to Southwest Austin and would like to plant a cluster of pines (or cypress trees?) or other fast growing, large and tall evergreen trees. Any suggestions?
view the full question and answer

Erosion controlling plants for a shady Minnesota lakeside
August 11, 2015 - I live about 50 yards from a lake and there is a steep embankment. Recently someone decided to cut the trees off the embankment and now the dirt is eroding off the embankment as well as off my back ya...
view the full question and answer

Best way to plant sedges on a slope in Fairfax, VA.
March 20, 2012 - Best way to plant sedges on a slope. WE are in the LONG process of trying to convert our backyard to a native wildlife friendly habitat. The slope is about 30 degress and it's a large space 1/2 acr...
view the full question and answer

Perennial blooming plants for Ashland MO
April 02, 2010 - I am beginning to create a flower bed in front of my house, I do not have a green thumb so I want to know what plants would come back yearly and I can plant now in Mid Missouri?
view the full question and answer

Selection of a small variety of Desert Willow for SE Texas
August 02, 2011 - Looking to plant desert willow as shrub. Any helpful tips to keep height down and plant full or bushy.
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.