Tuesday, 20 March 2018

Chain of hearts attracts (aptly) blood-sucking midge


There are more than 200 species of Ceropegia, one of them much loved as an indoor and sometime outdoor plant called Chain of Hearts, or some other variation on the theme of hearts, unavoidable given the shape of the leaves. The word rosary gets into some common names, playing off the chain metaphor.


Ceropegia is in the nowadays very large family Apocynaceae, with lots of other milky-sapped genera, such as oleander and frangipani. It sits though with the vast majority of the genera, and more than half of the 5000 or so species, in a subfamily called Asclepiadoideae, along with the closely related fellow succulent Stapelia, with its soft, unpleasant-smelling flowers.

Most species of Ceropegia grow naturally in Africa but they extend through into Asia. My illustrated species is Ceropegia woodii (sometimes called Ceropegia linearis subspecies woodii), from southern Africa and my specimen is a pink-tinged, variegated cultivar. Although some side shoots produced almost entirely pure white leaves.


The flowers are like hemorrhoiding vases. They capture insects, temporarily. While the insect is rummaging around inside the floral tube it gathers or delivers pollen. About 60% of species have an exclusive relationship a single genus of pollinator, the rest we would describe as generalists. A blood-sucking midge favours this small-flowered Ceropedia woodii.

Most visiting midges are female, and it's thought the flower is mistaken as a suitable egg-laying place. Typically the larvae of midges such as those that pollinate Ceropedia woodii feed on rotting plants and fungi. The pollen is almost always attached to the mouths of the midge.


Apart from looking like a rotting flower or fungus, I guess, the flowers have a perfume attractive to broody midges. Sometimes we can smell it. In the single flower I found, there was no attractive or unattractive perfume that I could detect.

In fact the role of the colours and various attachments on Ceropedia flowers are still not fully understood. They may add to the appeal of the flower once the midge has been guided into the general vicinity by the perfume.


This particular species of Ceropegia, but not all of them, produces potato-like tubers at the leaf junctions (below) and these can be used to propagate a new plant. The easiest way is to layer the intact stem onto moist soil, before you separate it from the mother plant.
  

More chains of hearts. More funny-looking flowers. More confused midges.

Thanks to Kate Cregan for her gift of the plant photographed, as a moving-in present a few years back.

4 comments:

Brittany said...

My Ceropegia is my favorite house plant! It flowers all the time and actually fruited once! Maybe a midge managed to find it's way into a couple flowers... or a confused fungus gnat??

Tim Entwisle said...

Fascinating. Yes possibly a confused tiny insect of some kind! Tim

Ross said...

This last weekend we dragged a rusted, bulging, mournful bit of old MMBW pipe back from a forlorn beach for our new crevice garden. We decided our chain of hearts would look good spewing out of its gape, so many thanks for your post Tim. You've fleshed out the whole shebang nicely.

Tim Entwisle said...

Sounds great. Pleased to be of assistance! Tim