3 Sisters made from clay

I have been experimenting with Native American farming methods. One of the ones that I have spent a good deal of time on is The 3 Sisters. You can read about it in the wikipedia entry I linked. This form makes sense to me, its companion planting to balance out each plants needs, and physically done so that squash (which like to be on hills) are appeased. Unfortunately I have found that the soil type has a lot to do with the success. My soil is clay. Brown, clumpy, and hard as a rock when it is dry. I've been told that it is the best soil once it really gets going.

Well, the mounds that the 3 sisters are in (actually I practice the 4 sisters since I plant sunflowers as well) are made of clay. "in time the Rockies may tumble / Gibraltar may crumble / they're only made of clay" Sure enough, yesterday in a heavy rain, my corn started to lean over. I thought it was weak roots and heavy rain. When I went out to look, I realized that the mound was simply disintegrating in the direction that the corn leans (east, toward the morning sun). The mound felt like a sponge in my hand. They fell over like dominoes, still rooted, but laying down, as they do in crop circles.

So now I have to stake them. Stakes for corn, isn't that supposed to be the other way round? ;)

So note to self, either prepare to stake, make some kind of border for the mounds to keep them in (a possibility with my infinite brick supply), or don't make hills.

I hope I can save them. They were chest high!