Thyme

Thyme asks for the opposite of what most houseplants want: poor soil, full sun, and long dry spells. Grown that way it is close to indestructible and its oils concentrate, which is where the flavour lives. Grown in rich compost on a shady sill it turns into a pale sprawling thing that tastes of very little. It is properly hardy, so a pot outside a door will crop through a northern winter, and it is one of the few herbs that is better in its second and third years than its first. Trim it by about a third after it flowers, cutting into green growth rather than the old bare wood, which will not shoot again. Replace a plant that has gone woody in the middle rather than trying to rescue it. Bees find the flowers before you do.