Thursday, December 10, 2009

Plectranthus Amboinicus aka Ant Killer

Plectranthus amboinicus is called Cuban oregano or Mexican mint among many other things (see gotham gardens for a post about all the names.) I think the one we have was a gift to my housemate that he planted outside. It died, but luckily a cutting was saved, potted and brought inside.

Its leaves are very soft and fuzzy, it has a delicious aroma, is used in Caribbean cooking, and evidently kills ants, or drives them insane until they starve to death. I'm still not sure which. If you look closely at the above picture you will see little ants on the leaves of the plant. They are all dead, many frozen in strange contorted positions. There are some more close-ups and a description of my "scientific" observation after the jump.

We found some ants starting a nest or something in the pot. A few of the leaves touch the edge of the pot and so as the ants circle around, some go up on to these leaves and try to explore the plant. I actually witnessed 2 do just this. One went up and up into the plant and then tried to turn around, but seemed completely confused. Even though it was sometimes very close to escaping, it seemed to have no idea where it had come from and just went back and forth to the same few leaves. The second ant didn't get far before it seemed disturbed and turned around. It took about 45s to a minute to find its way back off even though it had only touched about 3 leaves. Once it was off the plant and back onto the pot it ran into some ants and then took off away from the ant trail in a totally new direction and zoomed around this way and that with apparently no sense of direction.

So my questions are does anyone have this plant and have they witnessed similar death and destruction, or does anyone know what is going on here? Does the plant have a neurotoxin chemical it secretes? Or does anyone use it for cooking?


  1. Interesting plant--anything that reduces the local population of Argentinian ants would be a real plus for me! I've noticed ant trails into some of my carnivorous pitcher plants, but unfortunately most of the ants seem to come right back out.

  2. Weird. Never even heard of the plant before, don't have much sympathy for the ants.

  3. Fascinating! I have one of these in a pot on my sunporch and love it for the look and the fragrance, but this is a new attribute to me. I guess we don't have Argentinian ants in SE Colorado. Wonder if it would be toxic to other ants? Going to discuss this with the owners of the herb shop that introduced it to me.