Ok wow lol, First off in order to get true seeds you have to be careful with cross pollination. In other words if your 2 plants were to close to each other the seeds you may have collected may not be true like you want. This happens when you have 2 of the same kind but different varieties of the plants. I hope that made sense. Also if your kale is of a hybrid they for sure will not be true.

Secondly, if the seed pods that were on your plants were still green when you cut them down then chances that they matured fully is very unlikely. Not only do the seed pods need to dry, but they need to dry or mature on a living plant.

Thirdly if you have to hot of a greenhouse then germination may not be good at all. Germination takes place best at cooler weather like 60 to 75 degrees, if I am not mistaken.

Fourthly I am not familiar with your kale, I have always heard of cabbage and kale with your pansies and violas and thought of them to be winter plants, so the best time to plant I couldnt tell ya on that one.

Fithly I wouldnt know either on the plants surrounding your existing kale, but if there were seed pods that fell from the plant they may have reseeded. Just like I said previously though if your 2 different kale varietys were to closely planted though you probaly will not have true seeds. So its very likely that the seeds are from your plant that cross pollinated with the other one. You can always just watch and see what happens, alot of time seedlings look totally different than a mature plant.

I hope that helps ya and Goodluck!!