Depending on the datura, the seedpod will either be a spikey (wear gloves) or smooth; both close to the size of a golfball. The seeds are ripe when the pods split. If you do manage to collect some pods, be sure to dry the pods out well; any bit of moisture will cause them to mold. I'm unsure if that'll hinder germination. Handle this plant with care; all parts are poisonous...

I have the lilac datura and the black currant one. The seed pods are so different. The lilac have spikes that are 'OUCHY' and the black currants are smooth. I`ve collected the lilac ones in the past but this year is a first for the currant datura. Right now they are the size of golfballs, but look like they aren`t even close to cracking open. Don`t want the frost to get them. AND I DO WANT THESE SEED PODS VERY MUCH!! Any advice would be appreciated. Thank you in advance.

I don't believe frost will hamper the seeds viability. Once the seeds are fully formed the pods can be taken and allowed to dry on their own. You can tell if it's ready to harvest once it is totally dry. This is how most seed can be taken...Also, store them in a container and keep the interior dry. I wrap up uncooked rice in tissue/toilet paper so any moisture present is absorbed by the rice.

Thanks mikepots for that bit of info. I took a pod off my bush yesterday and brought it in the house. I have it laying just on my countertop. It is not brown-colored like it is drying yet. But it is huge! I have other pods on the plant. I will let them go to see if they crack open on their own. Again thank you.

I usually bring in the pods when they are still green. I put them in a shoebox where they turn brown and then pop open. But be careful as the seeds can explode out of the box! After they open I spread them out on a cookie sheet pan and let them dry THROUGHLY or they will mold.
I've collected them this way for years and have excellent germination.