I think growing and using seeds and leaves medicinally requires a lot of knowledge which you could only gain by going on a course. A lot of plants which can be used medicinally can be extremely dangerous when used in the wrong way.

Harvesting seeds to grow next year: Leave the seed head on the plant until the seeds are ripe, then cut off the seed heads and drop them into a container where you can separate the seeds from the cases. You can then store the seeds in airtight containers in a cool place. (Some people just put them in envelopes, but airtight is better if you can manage it)

Harvesting leaves, if you are quite sure you know what you are doing: You can cut the whole stem and hang it in a shady place with good air circulation until the leaves are quite dry. Then crumble them as required and store in airtight containers.

Thank you,but how do i know when seeds are ripe?

They usually go brown or black. The seed cases usually go dry and the seeds usually fall easily - hold a bowl underneath and tap them. If the seeds are still green they won't be ripe.

Thank you Steragram. bo banglesx