Where can I buy salsify seed?
We cannot recommend specific places to purchase. We can, however, offer information on the care of the plant:
Should you start Salsify indoors?
Salsify does not transplant well, so it is best to plant it directly out in your garden.
Salsify "Sandwich Island" was sown in three sites in April and May. All have germinated and produced good leaves but have not flowered. Should I leave them in the ground for another year (not very convenient)or lift them over winter?
Even though they are biennial, they are grown as annuals and are best harvested in cool weather. Those with mild winters should plant in fall and harvest during winter. Those with cold winters should plant in spring. Hot weather will make the roots stringy. Are you growing them for the flowers or as a vegetable? The leaves are edible, too. Here are the growing requirements that should help:
https://www.gardeningknowhow.com/edible/vegetables/salsify/grow-salsify.htm
https://www.gardeningknowhow.com/edible/vegetables/salsify/harvesting-and-storing-salsify.htm