How Often Should You Water Rosemary Plants?

They say that wherever rosemary thrives in the garden, a woman is in charge of the household. Whether or not this is true, if you cook, you will be glad to have a rosemary shrub (Rosmarinus officinalis), with its pungent needle-like leaves so useful in the kitchen. Planted correctly, few herbs are less demanding. Established rosemary growing outside needs little supplemental watering.

Rosemary hails from southern Europe and western Asia where it grows wild in sandy soils and rocky scrub. The Mediterranean climate boasts warm summers and mild, dry winters, and these are the growing conditions the evergreen herb prefers. The bush grows outdoors in U.S. Department of Agriculture plant hardiness zones 8 through 10 where it can grow to 6 feet tall with a 4- to 5-foot spread. Rosemary is drought-tolerant, and established garden specimens generally get all the water they need from rainfall.

You'll probably need to provide supplemental water to a rosemary plant in desert climates or in times of drought. Newly transplanted rosemary plants also need watering until they establish strong root systems. In these cases, the key is to provide occasional deep waterings that favor deep root growth rather than surface watering that encourages shallow roots. Don't water on a regular schedule. Instead, let the dryness of the soil tell you when it's time to water. Water the plant when the top few inches of soil feel dry to the touch.

When it comes to rosemary, drainage is as important, if not more important, than correct watering. Your rosemary plant's worst nightmare is to be stuck in wet, heavy soil. If this comes to pass, the shrub won't survive long. Rosemary does not tolerate having soggy soil around its roots and it may get root rot. Its native soil is sandy or rocky, and poor to moderately fertile, but the shrub grows well in any soil with excellent drainage. Rosemary also needs at least six hours a day of direct sun to thrive, but partial shade won't be fatal.

If you grow rosemary in containers, outside or inside, you need to water the plants. But first, make sure the plant has proper drainage. Check for drain holes in the bottom of the pot, then put in a 1-inch layer of gravel. Grow the rosemary in an even mix of sterilized soil, peat moss and perlite. Water the plant thoroughly whenever the top few inches of soil are dry. Take care not to overwater a potted rosemary because this encourages root rot. For outdoor plants, make sure the container is sufficiently large that six hours of direct sun won't dry it out.