Particles to suddenly appear

I’m trying to get a particle system to suddenly appear and can’t seem to get it in any sort of normal way.

When I start an animation with a particle emitter on a layer that isn’t rendered, no particles are ever created even after the mesh is later moved to a rendered layer.

What I can do is to set the starting layer to render, bake the emitter and then reset the layer so that it doesn’t render. This gives me the effect I want but seems to be the wrong way to do it.

Is there a better way?