How To Grow Rosemary
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Whether bush style or cascading down walls, this fragrant and flavorful herb is a wonderful addition to any garden. Learn how to grow rosemary.
Although rosemary is native to the Mediterranean, it thrives in my garden in USDA Plant Hardiness Zone 7a too. By midsummer, I’ve got fresh bunches large enough to clip. Read on to learn how to grow rosemary in your containers, raised beds or in-ground garden.
Types of Rosemary
There are two basic types of rosemary, upright and cascading, although there are plenty of named varieties within them. There may be only a few varieties to choose from at your local nursery or box store. If you want a certain variety for a specific purpose, like cascading down a rock wall, you’ll probably need to order it online.
Upright types grow four feet tall and wide. They’re drought and deer resistant and grow in poor soils. In warm climates like Zones 8 to 11, upright rosemary is an evergreen bush, attractive to bees and other pollinators.
If you’re growing rosemary for eating, choose an upright variety with wider leaves. These contain more essential oil, which gives them more flavor.
Upright rosemary is also considered hardier, preferred for cooler climates. ‘Arp,’ is one of the most tolerant of cooler weather and wetter soil.
For a ground cover that tumbles over walls, raised beds or containers, choose cascading rosemary. Although it isn’t as flavorful as upright rosemary, it can still be used for cooking and features beautiful blue flowers pollinators crave.
Creeping or cascading rosemary grows a foot tall, then spreads horizontally. Like upright rosemary, it grows in poor soil and is deer resistant.
How To Plant Rosemary
Although rosemary can be planted from seed, most people grow it from transplants or cuttings (see below). Seed germination is extremely low, and growing from seed takes an additional year.
- Wait until well after your region’s last frost date. Soil temperatures should be 70 F. To measure your soil temperature, buy a soil thermometer.
- Choose a spot that gets full sun. Rosemary needs at least six hours of sun per day.
- Ensure the soil has sufficient drainage, as rosemary cannot stand wet soil. This makes it well-suited to container gardening. Rosemary is one of the best herbs to grow in a patio garden.
- Dig a hole slightly larger than the transplant pot. Space rows far enough apart to allow rosemary room to grow. It grows two feet tall and wide in one summer. If it overwinters — most successful in raised beds in Zones 7 to 11 — it will eventually be three to four feet tall and wide the following year.
- Add a handful or two of compost to the hole, working it into the surrounding soil.
- Fluff up the roots and plant the transplant.
- Mulch lightly around the planting area, then water.
How To Grow and Care for Rosemary
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Be careful not to overwater. Established plants are drought tolerant, but too much water can cause root rot.
Only water rosemary once a week or every two weeks, and let the plant dry out between waterings. Rosemary leaves do not wilt like those on other plants unless they are diseased. If you use drip irrigation, place it a few inches away from the plant to keep from overwatering.
Prune rosemary in summer after it flowers to encourage bushy growth. If it has overwintered in your garden, prune it in early spring for rapid new growth when temperatures rise. Try not to cut too far into the main part of the plant; rosemary won’t grow from old woody stems.
Rosemary does not need fertilizer. It’s conditioned to grow on rocky Mediterranean slopes. Overly rich soil can grow leggy plants that are more susceptible to insects and disease.
Save money by taking cuttings in spring or early summer.
- Clip a two to three-inch branch from the top growth.
- Strip the lower leaves, leaving an inch of leaves at the top of the stem. Dip the stem in rooting hormone gel before planting. I like the gel better than powder because it stays on the stem.
- In a four-inch pot, plant two or three cuttings at the edge of the pot in regular potting soil or a cactus and succulent potting soil.
- Gently water your cuttings.
- Place the pot in indirect sunlight.
- Water when the soil becomes dry.
- After about eight weeks, your cuttings should be rooted and ready for transplanting.
Outdoors, rosemary isn’t bothered by many insect pests because its natural oil repels them. However, indoors, you may see aphids, mealybugs, whiteflies and spider mites. To control pest infestations, spray plants with neem oil.
Prevent most diseases by not overcrowding plants, not cutting into woody stems and not overwatering. Also, be aware of these issues:
- Powdery mildew, which looks like white powder on plant leaves and stems, is seen in humid climates or on rosemary grown indoors. Rub off the powdery substance. Spray with neem oil if the powdery mildew persists.
- Root rot shows up as wilted and yellowing leaves, or in extreme cases the leaves are brittle and gray. Roots will be soft and mushy. It is caused by overwatering or bad drainage. It’s best to pull the plant and start over.
- Botrytis can look like gray mold or brown spots on stems eventually causing the entire plant to wilt. It is only a problem in humid areas or on plants grown indoors.
- Bacterial crown gall is caused by cutting into woody stems. Tumor-like swellings show up on plant stems often just above the soil line. It doesn’t usually affect younger plants. It can stunt the growth of larger shrubs, but it is slow acting. Remove shrubs that become unsightly.
How To Harvest Rosemary
If using fresh, harvest rosemary tips only. The youngest part of the plant has the most flavor. Use kitchen shears or microtip pruning shears to trim tender stems, and don’t cut into the woody parts of the plant.
To dry rosemary to use later, cut stems about five to six inches long before they flower in late summer. Tie the cut ends together with twine and hang them upside down in a cool, dry location.
Although fresh rosemary has the most flavor, dried rosemary tastes great in soups, stews, stuffing, and as part of a rub for grilled or roasted meats.