Is it possible to limit the "Cycles Shadow from Transparency" per Object? There is an option in the properties panel, Render > Light Paths > Shadows that toggles "using transparency of surfaces for rendering shadows" for the whole scene.

I like to render architectural stills or short films. When I uncheck this option the rendering speed greatly increases, but some parts such as fences and curtains don't work very well, although the quality of shadows of trees, grass and so on is sufficient.

How is it possible to change this option per-object?
There will be a &quot;Transparent Shadows&quot; option per material in version 2.68 and the latest Blender builds.
Using a Light Path node to disable transparency helps and achieves the same visual result, but it still needs to execute the shader to find out, which costs some performance.
Update:
This is now accessible in materials &gt; settings: