Tuesday, June 21, 2011

Wild Petunia

The abundant rainfall has certainly spawned a crop of robust wildflowers at Blue Jay Barrens. Certain plants, like this Wild Petunia, Ruellia humilis, bloom every year regardless of the weather, but they are expressing themselves particularly well this year.

The tubular flowers don’t last very long and are often ready to drop the day after opening. Fortunately, the blooms develop in a long succession, so there is an extended period of time in which you can find blooms on the plant. The fused petals drop as a single unit, which sometimes litter the ground following a heavy rain or wind storm.

The stems are square with a variable amount of hairs. That variability also pertains to other parts of the plant. There can be such a wide variation in characteristics between plants that you sometimes wonder if you are dealing with more than one species.

To complicate things, there are two other Ruellia species that may be found in this same area. Ruellia strepens is also found at Blue Jay Barrens. One characteristic that separates the two is the width of the calyx lobes, which are the long pointy leaf-like parts attached at the base of the flower. Strepens is wider than 2 mm and humilis is less than 1 mm. An easy enough difference to check unless your measurements are consistently 1.5 mm, like the ones I keep getting. There’s also a rarity called Ruellia caroliniensis which is identified by the length of the leaf petiole. Less than 3 mm is humilis and more than 3mm is caroliniensis. What measurement do I always get? Of course it’s 3 mm. The only thing I can do is check all of the characteristics and go with the species that most closely matches.

Ruellia humilis can grow right in the roughest of the barrens. Even with more than twice the normal spring rainfall, the ground has already developed drying cracks. I keep looking for Ruellia caroliniensis, but so far none I’ve found none. It has been reported several times within a mile of Blue Jay Barrens, but it seems that shortly after being discovered, someone else decides that the identification was in error and declares the plant to be just another Ruellia humilis.

Wild Petunia is a perennial plant, so the luxurious growth should result in an expanded root system that will allow for another super growth season next year. It’s always the year after the abundant rainfall that these dry areas are most impressive. This is especially true if the next year is abnormally dry. The dryness will suppress the growth of plants not adapted to the dry harshness of the barrens, but the true barren plants will flourish. I hate to wish for a dry spring, but if it happens next year, the barrens will look spectacular.


  1. Hi Steve...a delightful post, especially after yesterdays...I don't know if it was the same kind but I found a hole like that once in my veggie garden, and to my surprise and FRIGHT a large spider came to the top...I thought I was going to die!! Haven't seen one since thank goodness!!
    Yes about this delightful little plant..cute as can be and very much likes the worst of soil. Plants in the wild grow in there own type of soil and environment they are suited for..... and people wonder some of there garden plants don't do well???

  2. great post, reminds me of a discussion I had with a professor at UC regarding IDing Trilliums. In for example the case of the Petunias,do you happen to know if the variants are all genetically tested at some point or are we purely going on mm measurement differences?

  3. Hi, grammie g. Yesterday I purposely started off with a shot of an empty hole just so you would have a chance to click away if you didn't want to see the spider.

    Michael, I'm not aware of any DNA work having been done with this genus. That kind of work is interesting, but it doesn't help me at all with identification.