How to Care for Rosemary Plants

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Proper care for rosemary plants (​Salvia rosmarinus​) helps this evergreen perennial herb thrive in your herb garden. Rosemary is one of those plants that multitasks very well. It prospers in hard-to-grow places, such as rock gardens and dry areas, and it provides you with a seasoning that can flavor your food all year long.

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A member of the mint plant family (Lamiaceae), rosemary is great for seasoning poultry, lamb, stews and soups. The Greeks and Romans noted its medicinal uses and mystical properties. In folklore, it was thought of as a plant that could ward off evil spirits.

Planting Rosemary Bushes

The best time to plant rosemary seeds or cuttings is after the last spring frost date in your area. If you want to get a head start, you can plant seeds or cuttings indoors, eight to 10 weeks before the last spring frost.

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Rosemary is a perennial in USDA plant hardiness zones 7 through 11, and it grows best in warm, Mediterranean-type climates. Plants may survive the winter and return in the spring in Zone 6 if planted in a sheltered area. If you live in an area with very cold winters, however, you can plant your rosemary in a container and bring it indoors for the winter. Rosemary grows very well indoors.

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When planting outside, plant your rosemary on well-drained soil that is about 70 degrees Fahrenheit. Choose a spot that gets at least six to eight hours of sunlight each day. If your soil is heavy and wet and doesn't drain well, consider planting in a raised bed or container. Make sure your plant has plenty of room to breathe and spread as rosemary plants can grow to 6 feet tall and equally as wide, depending on cultivar.

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Care for Rosemary Plants

Water deeply once or twice a week throughout the growing season, depending on the weather. Don't overwater as rosemary is subject to root rot. It's best to let the soil dry out before you water your rosemary plant again. Fertilize occasionally with fish emulsion. In the spring, use a slow-release fertilizer.

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Prune the rosemary stems using sanitized pruning shears when the plant starts to look ragged. That will give your plant a nice, bushy look and encourage better growth. Try to cut above a leaf joint, and prune no more than one-third of the entire plant at a time. Prune out any dead-looking stems.

Growing Rosemary Indoors

Rosemary has a wonderful scent and is a popular indoor plant. If you're growing rosemary in a pot, let the soil dry out each time before watering again. Put your finger into the soil a couple of inches deep. If it feels dry, you can probably water.

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Choose a sunny indoor spot so the rosemary gets six to eight hours of sunlight each day. It's a good idea to rotate your indoor rosemary plant so all sides get plenty of sun. If you decide to plant your indoor rosemary outdoors in the spring, remove it from the pot, cut away dead and circling roots and break up the root ball before planting.

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Propagation of Rosemary

Rosemary grows very well from cuttings. Cut a 6-inch piece of new growth from an established plant. Remove the lower leaves several inches from the bottom and dip the bare stem section in rooting powder. Press the cutting into dampened, soil mix with good drainage. Soil mixed with equal parts perlite and peat moss does well. You should have root growth in two to three weeks.

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Rosemary Plant Diseases

Rosemary can suffer from powdery mildew, which is a white, powdery fungus that develops in humid areas with little air circulation. It won't kill the plant, but it could weaken it. You can lessen the chance of your plant getting powdery mildew if you keep it pruned and make sure it has plenty of room.

Red spider mites and black aphids can also attack rosemary, especially in winter. Control these pests by spraying all parts of the plant with an insecticidal soap, observing all label directions. You may have to spray your plant weekly or biweekly to control the pest infestation.

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