Why Do These Trilliums Have a Green Stripe on Each Petal?

Just before or on Mother’s Day in southern Ontario the Trilliums burst into bloom. As I’ve been wandering through the woods this April and May I’ve been trying to take photos of all the types of trilliums I see. Colourwise, I’ve found white and red trilliums. As the white ones age, many will gradually fade to a light pink. The most interesting white ones had a broad green stripe down each petal.

Where Do These Green and White Trilliums Grow?

Photo of White Trillium Green Stripes on NaturalCrooksDotCom

Although I’ve looked elsewhere, so far I’ve only seen these white and green trilliums at Bronte Creek Provincial Park. They are quite striking.

When I looked closer, I found some are almost entirely green. They are less noticeable as they blend in with the green leaves.

Photo of White Trillium Infected Mycoplasma on NaturalCrooksDotCom

According to information provided by Bronte Creek, the green stripe is caused by a virus.
A University of Alberta website cautiously states that the stripe may be caused by a bacteria or virus.

A Michigan State University website on the Painted Trillium is a bit more specific. It says “Trillium grandiflorum (Large White Trillium) … [can be] infected with virus-like mycoplasmas, which are parasitic, subcellular organisms that often result in the normally white petals being streaked with green or pink….” It says this type of infection is “not uncommon.”

The basis of the Michigan comments was a source called “Case.” In a chat about green-striped trilliums, another person says “To my knowledge there has been no direct DNA work done to confirm and expand on the Case, et.al. observation of mycoplasmas in trillium.”

So I’m not 100% sure what causes the green stripes, but the most accepted theory is that it is an effect caused by mycoplasma.

Photo of Red Trillium Lemoines Point On NaturalCrooksDotCom
This is a Red Trillium near Kingston in 2013.

Do Ants Really Plant Trilliums?

I’ve read this idea on websites and in books. I guess it may be true although I find it surprising.

Photo of White Trillium on NaturalCrooksDotCom

Apparently ants collect the seeds from trilliums and take them away from the plant and sometimes underground. They eat only a portion of the seed and the remainder can sprout and start a new plant. (That’s similar to birds eating buckthorn berries, digesting the outer fruity layer, and then shedding the undigested seeds which may grow into new shrubs.)

Photo of Trillium Fading Pink on NaturalCrooksDotCom
This photo was taken last year of a white trillium fading to pink which will soon set seed.

If you’ve seen ants taking the seeds away from a trillium please let me know with a comment. I’ve never seen ants anywhere near a trillium, myself.

Photo of Red Trillium Red Sepals On NaturalCrooksDotCom
This Red Trillium has red on the edges of the green sepals, too.

For now, I will enjoy every shade of trillium I find.


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Have you seen any of these striped trilliums? Or seen any ants toting away the trillium’s seeds? Please share your experiences with a comment.

10 thoughts on “Why Do These Trilliums Have a Green Stripe on Each Petal?

  1. We have trillium striped with green here in Brantford, Ontario long the Grand River. I have seen them in the same area several years in a row.

    • Sounds like another good place to look for them! The virus seems to stay in one area for many years, if not for ever. The ones at Bronte Creek have had this colouring for more than 15 years that I know about.

      Thanks for sharing your sighting!

  2. By the way, the “Case” source you mention above is a really great book on Trillium by two long-time Trillium enthusiasts and botanists, Fred and Roberta Case’s “Trilliums” (1997, Timber Press).

    In it, they describe some work from the seventies where abnormal flowers (like the ones you posted) were examined with an electron microscope. Mycoplasmas (very very tiny bacteria that live *within* host cells) were present only in the abnormal flowers and not in normal-appearing flowers. So right now it’s guilt-by-association. Mycoplasmas also cause “parrot tulips” distinctive flowers.

  3. Today at LaSalle Park in Burlington, amongst a large number of trilliums I saw a single trillium flower with a green stripe down the length of each petal, like the top photo. It really stood out from the normal flowers. I didn’t search them all but if there were more it wasn’t too many.

    • Interesting! That’s another place then where the virus has started to sneak into the trilliums. I saw some at 16 Mile Creek too. Thanks for sharing your sighting!

  4. I would love to send to you some pictures I have taken of Trilliums. How would I do this.

    Sincerely,

    Donna McAdie

  5. Lawson Tract by Ingersoll ON also has a few of these green striped trilliums as well as solid green ones. I just assumed it was a cross pollination thing such as I see in my tulips where the red and yellow start blending when grown together. A friend just mentioned it to me that it was bacteria. Her information indicated that it would eventually kill the plant. Has there been any research into this? Should they be removed from the ecosystem?

    • I couldn’t find much research into this at all. In fact, almost all the websites just quote each other and refer vaguely to the one study that concluded it is probably (not proven) caused by a virus. I haven’t seen any sign of it killing the plants. I personally would not remove them from the ecosystem. I’ve seen enough info on websites to believe that these types of trilliums are quite common.

      If anyone has seen this actually killing plants, please share!

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