Superimpose roses

[ulra7]

I wish to plot two series in the same figure. Like this:

The figure above was produced by plotting the two roses separately, removing the axes for the orange part, saving them as images, and then using image.paste()

I am trying to get the same result from plotting directly on the same axes. What I am getting is this (please ignore the labels and legends, the problem is with the plot itself):

My code (for the second image) is:
`fig = plt.figure()
ax = WindroseAxes.from_ax()
ax.bar(st.Direction,
st.Value,
bins=bins,
normed=True,
cmap=cmap.get_cmap('Blues'),
edgecolor='none',
zorder=0)

ax.bar(mod.Direction,
mod.Value,
bins=bins,
normed=True,
cmap=cmap.get_cmap('Oranges'),
opening=0.55,
edgecolor='none',
zorder=10)`

It doesn't look right at all. The blue and the orange plots swap order. I am getting the same effects with or without zorder. I have tried using ax.twinx() but that returns a ValueError: Cannot set Axes adjustable to 'datalim' for Axes which override 'get_data_ratio'.