Sunday, June 29, 2014

Blooming five-angled dodder (Cuscuta pentagona) in Tandy Prairie

Blooming dodder, heavily parasitizing its host.
The family Cuscutaceae, formerly lumped with the morning glories (Convolvulceae), are a very unusual bunch. These plants are parasites. They don't produce their own chlorophyl, so they survive by by tapping the phloem of a host. They can tap multiple plants at once, and can serve as a disease vector, spreading viruses from one individual to another. I was excited to catch this piratical plant in bloom in Tandy Prairie last week.

You can see a little bit of the host's yellowing in the photo above, but it was much more extensive than I captured in that image. Seems like a bad parasite, right? To kill your host? But I suppose if the dodder can tap a new host once its old one expires, then perhaps it doesn't have to be so committed to only taking what can be spared.

Funky flowers, closer up.

Interestingly, dodders start with a root, but it dies off once they find a host. They grow airborne. These plants are so totally committed to parasitism, their seeds don't come provisioned with cotyledons.

Apparently, these plants even have what could be called a sense of smell.  When they germinate, the seedlings sniff the air and grow towards volatiles coming off a suitable host. For example, in one experiment they preferentially sought tomatoes 73% of the time. Weedy or not, I think I love this little plant. It is so weird.


  1. I've heard of dodder but never seen it. What keeps it under control? Is it a North American native?

    1. I'm not sure what keeps dodder under control- perhaps the most seeds (being unequipped with cotyledons) aren't viable. Most of the dodder you see is native, but there is an invasive japanese dodder. It looks pretty distinctive. The flowers come off on little bunched stalks instead of budding along the stem. I don't think I've ever seen japanese dodder.