Cabbage

Water drops on an outer cabbage leaf
Water drops on a cabbage leaf. Image courtesy of Lynn Greyling, CC0 Public Domain

When we wash plants in the cabbage family (which includes Brussel sprouts and broccoli), we see that water easily bounces off the leaves. This is a clear indication that they are superhydrophobic. The superhydrophobicity is caused by wax towers on the surface of the leaves. We can see this in the Scanning Electron Microscope (SEM) picture on the right below. The structure is quite different to that of the lotus, which looks more like a collection of hillocks, even though they have bumpy waxy surfaces.

Water drop in a cauliflower leaf
Water drop in a cauliflower leaf. Image courtesy of Lynn Greyling, CC0 Public Domain license
SEM image of a cabbage leaf
SEM image of a cabbage leaf

Hydrophobicity can present a problem for farmers wanting to spray plants that are diseased or have been attacked by insects because sprays can bounce off them just as water does. Fortunately, the addition of a little surfactant to the spray prevents this. Surfactant is usually present in commercial spray formulations .

Click here to see a demonstration of the superhydrophobicity of cabbage leaves by the Science Museum of Minnesota.