Hardy annuals like borage and marigolds may be sown in spring or in the autumn if you want them to provide flowers late in the next spring. Biennial herbs like caraway and angelica may be sown outdoors in late summer or early autumn to provide flowers in the following summer. Thin out the seedlings twice: once after germination so that two or three remain at each position and again after a few weeks so that only the strongest plants will remain in place.
Hardy herbs that are used regularly in large quantities like parsley, coriander and chervil, may be sown at intervals of 3-4 weeks from early spring to early autumn to provide a succession of foliage for harvesting throughout the year. In colder regions they will need protection from frost with cloches so you can harvest them even in winter.
Chervil and dill are easy to grow from seeds but they are difficult to transplant and that is why they are best sown directly in their final position. Basil is one of the more difficult herbs to grow from seeds in cold areas as it needs higher temperatures to develop than other annual herbs. Sow basil seeds very thinly in late spring and keep it at a temperature of at least 13 Celsius degrees (55 F). Prick out seedlings when they are large enough to handle and keep them in a sunny, well-ventilated place. If the conditions are cold and damp, basil seedlings are prone to damping off and grey mould. Plant out basil seedlings once all danger of frost is past or, in poor summers, grow them in containers under cover. In warm areas you can sow basil directly into an outdoor seedbed.
Perennial herbs may also be grown from seeds. Sow them in warmth in spring and grow on the seedlings in pots until they are large enough to be hardened off and plant out. Plant and care for them as for container-grown herbs. Most cultivars of perennial herbs do not come true from seeds and they must be propagated by cuttings or layering. Variegated rue is one an exception to this rule. Also the non-flowering forms, such as lawn chamomile, cannot be raised from seeds. You can only propagate it by cuttings or division to obtain new plants.