I thought I would share my thoughts on tithonia seed and this probably would apply to sunflower seed and other things. I pick the seed pod when it is just short of being entirely dry and break it apart. You can see the seed very clearly as they are black and the chaff is a pale color. I believe the seed will be viable picked at this stage and it is a lot easier than waiting until the pod is entirely dry when the seed and chaff look very much alike.