How to collect seeds of wild plants?

Hello, this is my first post in this section!
I'm Fabio from Italy and I'm a farmer trying to convert the farm into a natural farm. I'm mainly following Jadam method and I am looking for wild plants that can be used into the JHS (Jadam Herbal Solution). I'm interested in control aphids and ants, because they really love my hemp plants, and some vegetables too.

I've found a wild plant, with a very strong smell: Inula viscosa. Unlucky the plants are few and grow on rocks...i would like to collect seeds and multiply for future use, but I don't know how. I'm quite sure the smell is a repellent for insects.

Thanks,
Fabio

Hi Fabio, it looks to me like a plant that you can propagate by dividing the roots stock in autumn. If you dig it out is it like a lot of roots together in a ball shape with sticks sticking out? If it is i think you can divide it with a spade into 4 and plant it seperate. I got this from the PFAF site. They call it Dittrichia Viscosa, check it out.

Propagation

Seed - we have no details on this species but suggest sowing it in spring in a greenhouse and only just covering the seed. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Division in spring or autumn.

PFAF

If i needed this plant i would find out if it's rare, if not, move it into my garden, let the seeds ripen as good as goes and pick them before the wind blows them, dry them store them in a paper bag and plant in spring

If it is rare, I don't recommend digging it up.  When I see a wild plant I want seeds from, I try to visit it at least once a week.  This way I can observe the flowers and see when they might be getting ripe.  I try to wait for some of the seeds to fall or blow away, so that I know the rest of them are likely to be ripe enough to pick.  I put seeds that need to ripen a little more into a paper bag and put it in a warm dry place.

hello! thanks for the replies. I will try to dig one and try to understand if i can multiply by roots.

From the PFAF website I've read it is in flower between september and october. Once the flowers die I would like to put a paper bag over the stem and tie with a string to save seeds..

I use organza bags.  They can 'breathe' very well and don't fall apart in the rain, or the sun.  I usually pop them over the flower before the seeds are ready and leave them on, sometimes for weeks, then snip off the entire flower or cluster of flowers with the bag still over them and hang them up in the dry until I get round to processing them.

Fabio, this is how to divide them.
They're Asteraceae, these are Asters, i expect them to be the same.