Re: Ruellia humilis

Claire --
I'm so glad you asked about Ruellia humilis.  It is one of my favorite 
Missouri natives and I am glad to find somebody else growing it. Around here 
it is called wild petunia (or sometimes hairy wild petunia to distinguish it 
from the other Missouri native, R. strepens).  R. humilis is known in some 
other parts of the country as fringeleaf wild petunia.  

This species is native to most of the eastern United States where it is 
commonly found growing wild on glades and open rocky hillsides, savannas and 
dry prairies.  

It is not native to New York, but it should be hardy there.  I think you can 
believe it is hardy to zone 4 because its range includes the northern parts 
of Michigan, Minnesota, and Wisconsin.  Looking at the plant's distribution 
map on the USDA online plant database (http://plants.usda.gov/plants), I 
would say it is hardy from zones 4 to10.  

You are right, it is difficult to find cultural information on this plant.  
There are some tropical plants in the genus and they are better known in 
gardening circles.  Our natives are difficult to locate in the trade and are 
seldom grown in gardens, except those of wildflower nuts like me.  

It is called wild petunia because the flower looks just like a petunia, but 
it is not related to the common annual we all know as petunia.  I think it is 
lovely, but it is a humble plant and not as showy as its namesake.  The 
annual petunias are in the nightshade family.  Ruellia is in the Acanthus 
(Acanthaceae) family.  

R. humilis is a perennial.  It does well in dry soil. It has a dense coat of 
fine hairs that protect it from evaporation. The lavender flowers appear from 
May to October. I believe a white flowered variation is sometimes found.  In 
the wild and in my garden it grows in full sun.  I don't know how well it 
would do in the shade.    

It is named for the 14th century French herbalist, Jean de la Ruelle.  
Humilis is Latin for low growing or dwarf.  That's about all I know about it. 
 Hope this helps and that you enjoy your wild petunia!  --Janis  

In a message dated 9/12/00 11:01:55 AM Central Daylight Time, 
perennials-owner@mallorn.com writes:

> Date: Tue, 12 Sep 2000 11:04:22 EDT
>  From: ECPep@aol.com
>  Subject: Ruellia humilis
>  
>  Hello Per-List:
>  
>  I have a newly acquired plant - Ruellia humilis.  I have thought this 
genus 
>  tender in northern states.   At the arboretum sale where puchased, I was 
> told 
>  this species is hardy through zone 4.
>  
>  Now, I am having trouble believing the zone 4 information.  I put my plant 
> in 
>  a cold frame for the winter.  Is there any experience out there with r. 
>  humilis or any ruellia hardy in the north.  There has been some discussion 
> on 
>  the Shadegarden List regarding this genus but I was told: full sun. 
>  
>  Ruellia does not seem popular enough to appear in catalogs or books in any 
>  depth.
>  
>  BTW, winter is a thought here. We had a light frost on September 5.  Now 
the 
> 
>  rains are back.  What a summer!
>  
>  Claire Peplowski
>  NYS z4
>  

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