This unfussy genus in the Mint family is native from Africa to Asia and the Pacific Islands.
Plectranthus argentatus is a vigorous grower in full sun or partial shade (required in warm inland areas of the West) and evenly moist soil. Plants should not be allowed to dry out. Pinch as needed to keep bushy and compact in annual containers or beds. Hardy to Zone 10 (30°F).
Plectranthus 'Mona Lavender' grows well as a houseplant in bright, indirect light or partial sun. A daylength of 12 hours or less promotes flowering. Day and night temperatures of 50-80°F are fine year round. Water when the top 1 inch of the potting mix is dry to the touch. Withhold fertilizer while your plant is in flower during the short days of the year. After flowering has finished, feed every 2 weeks with a water-soluble fertilizer that is lower in phosphorus (such as 20-10-20) mixed at ½ strength. Keep your plant compact by occasionally pinching off the tips of new shoots. This allows side branches to develop. Cut off flower stalks when their blooms have faded. About once a year, repot into a larger container (one that is 1-2 inches greater in diameter), using a well-drained potting mix.
For information on planting and care of annuals, click How to grow annuals.