Agree with Steve's comments above.
I find that Lily pollen can some times be hidden in the carpets fibres and not noticable until water/prespray hits it and then you find a massive stain appear.This can become permanent on wool but usually if treated quickly can be totally removed.
Similar to Stuart, my first line of defence is eco spotter as it is alcohol based and threfore will help disperse the moisture to allow the microspltin propertis of the spotter to remove the pollen. This usually takes a couple of his before xtraction.