Posted: 03/05/2017 at 19:19
non of the named cultivars can be relied upon to come true from seed
Stipa tenuissima is easy, seed around the garden, you'd have some flowers next year. I have never had a seedling from S. gigantea which suggests it's not so willing. Grasses are generally easy though.
Phlomis are very easy as well but it will be P. tuberosa not the cultivar 'Amazone' (whatever the seller tells you) it will be seed from 'Amazone'. A few flowers next year maybe.
Heleniums are easy but you don't get those lovely russett/oranges (at least, I didn't)
A quicker and barely more expensive option is to buy one plant and use it as propagating material rather than flowers for the garden. Cut the flowers off and take cuttings or split up