Using natural outisde plants and roots?

When you use natural outisde plants and roots in your scenery , must you preserve them with glycerin?

I think for roots, twigs, small bits of natural wood elements, you don’t need to … Well, I never have…

I think the glycerine is for more like ferns, leaves etc … It is meant to (I think) basically push out the plants natural water content, and the glycerine then takes its place …
I watched some YouTube clips about, bought the glycerine, tried it and failed epically with it…

Others have mentioned they just mist over the plants with plant coloured paint …

I’m sure other will have different methods …