Growing Herbs Indoors Under Lights in Winter

Any advice for growing herbs indoors under grow lights for the winter. My purple basil is barely holding its own. Rosemary seems to be thriving.

Light is the critical factor for success growing herbs indoors in winter. Herbs need stronger light than many house plants but most gardeners jump to the conclusion that light that is adequate for other house plants will be sufficient for herbs. If rosemary is thriving and its stems are not "reaching" for light then light levels are high enough.
Purple basils (Dark Opal, Rubin and Purple Bush varieties) are annuals. They need to be replaced when they become woody and growth slows. Such plants usually die over winter when grown in natural light. Under artificial light the signs of aging can occur anytime after six months. The solution is to start new plants from seeds (in the case of Dark Opal and Rubin) or from cuttings.