How to Take Care of Rosemary Plants

If you're looking for an edible, aromatic, ornamental and fairly low-maintenance plant requiring minimal watering and fertilizer, look no further than Rosemary (Rosmarinus officials). Although this woody shrub isn't pest-free, you can minimize problems with regular inspections and treatment. Rosemary grows in U.S. Department of Agriculture plant hardiness zones 8 through 10, reaching up to 6 feet tall. Its flavorful needle-like leaves go exceptionally well with roasted meat dishes and stews.

Rosemary plant
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Rosemary plants flower in the summer, attracting bees and other pollinators.

Sun, Soil and Fertilizer

The key to success with rosemary is lots of sun -- at least six hours a day -- and soil that drains well such as sandy or loamy areas. Avoid low-lying areas where water tends to collect and heavy clay soil. Consider a raised bed for rosemary if drainage and heavy soil is a problem.

In the spring fertilize rosemary once with 5-10-5 fertilizer. Use 1/2 cup of granular fertilizer for each foot of height sprinkled on the soil around the base. Water after distributing, rinsing off the needles to remove fertilizer residue.

Watering and Problem Prevention

Rosemary comes from dry Mediterranean climates and, having adapted to this growing environment, is susceptible to rot problems when overwatered. Water sparingly, waiting until the top 2 to 3 inches of soil starts to dry, then lightly dampen the soil 5 to 6 inches deep. Water slowly so it can soak into the soil. A general guideline is 1 inch of water per week, but adjust the amount to account for rain, slow drainage and damp weather.

Pests and Treatments

Look for pests regularly -- a weekly inspection is sufficient. Spittle bugs create spit-like foam on the needles but don't cause serious damage beyond the messy foam. Wash these off with water and get rid of the bug hiding underneath by picking or rinsing it off. Webworms do more damage. These caterpillars create a tent-like structure on the branch tips. Cut off and destroy an affected branch as soon as you see the tents (called bags) forming.

Aphids and Spider Mites

Rosemary occasionally attracts spider mites or aphids. Both these tiny sap-sucking insects feed in colonies. Spider mites create a fine web-like structure between the needles accompanied by the tiny white insects, while aphids are more likely to appear green or pale white and feed on the underside of needles and other protected areas. Wash the bugs off with water. Rosemary is fairly tough, so you can give it a good strong spraying. If water doesn't do the trick, spray aphid or spider mites with ready-mixed insecticidal soap. Apply it directly to the insects until the area is damp. Wear protective clothing and eye wear when handing pesticides, and keep all containers out of reach of children and pets.

Pruning and Harvesting

Regularly snipping branch tips for cooking or drying keeps rosemary looking trim and bushy and maintains a constant supply of fresh herbs in the kitchen. Pinch or snip the green branch tips as you need them with a pair of shears or scissors. This naturally bushy shrub doesn't need regular pruning other than to remove broken branches and damage.

After pruning or snipping rosemary branches, wipe tools down with rubbing alcohol to sterilize the blades.