Thyme can be easily propagated from leaf-tip cuttings or division of mature plants. To divide a large plant, remove the plant from the pot and gently tease apart the root ball and stems, then plant each ball in its own pot. In most cases, however, it's usually easier to discard older, woody plants and buy new thyme plants. Thyme can also be readily grown from seed, which opens up a larger selection, such as lemon or Spanish thyme. Thyme seeds germinate in one to three weeks.Most thyme plants are only repotted after their initial purchase, perhaps stepping up from the 4" nursery pot into a 6" pot, which is plenty large enough to support a thriving and healthy thyme plant. Older plants develop a woody stem. You can divide older plants at repotting time and place them back into 6" pots with fresh soil—there is no reason to grow thyme in larger pots for kitchen use, especially if the thyme is part of a collection of kitchen herbs.