Rosemary (Salvia rosmarinus) is a tasty, aromatic herb that's native to the Mediterranean. Popular in cottage and herb gardens, it has pretty blue, lavender, pink or white flowers and evergreen needle-like leaves. In the right conditions, rosemary can thrive in your garden or home. Although it's generally a low-maintenance plant, you should consider your local climate and soil before planting. Once you've learned how to care for this herb, you can enjoy its foliage, fragrance, and savory flavor year after year.
There are over 20 cultivars of rosemary to choose from, ranging from traditional upright shrubs to low trailing varieties. Although all can be used for cooking, upright ones such as Tuscan Blue, Blue Spires, and Miss Jessup’s Upright contain more aromatic oils. Blue Boy and Golden Rain are smaller, compact varieties that work well in containers. For colder and wetter climates, consider Hill Hardy, Arp, or Salem.
Rosemary has been grown in the United States since the early 17th century and does best outdoors in frost-free zones. Rosemary's name means "dew of the sea" and it will flourish in warm coastal climates such as California, which are similar to the Mediterranean. In zones prone to frost, it can be grown as an annual or brought inside during the winter. Some varieties are hardier than others, so always check the label to make sure it suits your local climate. Plant in a position that gets full sun throughout the day, ideally south-facing.
Rosemary does best in sandy, free-draining soil with a neutral or alkaline pH. If the soil is too acidic, consider planting your rosemary in a container or raised bed with sandy soil and good drainage. If you're not sure what type of soil you have, see if rosemary is growing in gardens in your neighborhood. Your local gardening store can also advise you. As a last resort,pick up a simple pH test kit to check the levels yourself.
Rosemary grows well in containers. This is especially good news if you live in a frost-prone area, have acidic soil, or have a balcony instead of a backyard. Make sure the container you choose has a drainage hole to prevent waterlogging. Repot your plant each spring, or start over with a new plant from your garden center.
It's best to buy a young nursery-grown plant as rosemary is difficult to grow from seed. Transfer the plant to your chosen container or garden plot, allowing it space to grow. Once it's established, you can take cuttings to start more plants for yourself or for others. For best results, you'll need a container, rooting hormone powder, and sterile seed starting mix from a gardening store. Cut a 2-inch piece of new growth, dip the cut end in rooting hormone and then plant in dampened soil. Place in a well-lit spot for two or three weeks until you can see root or new leaf growth. Then transfer the cuttings to individual pots.
Rosemary is drought resistant and prefers to be on the dry side, so only water when the soil is completely dry. To check, insert your finger into the top inch or sosoil. If it feels dry, it's time to water. If you have plants in containers, don't let the soil dry out completely in the summer heat. Likewise, don't overwater, as this can lead to root rot which will kill your plant.
Outdoor-planted rosemary can grow to six to eight feet high, so you may need to manage its size. You can prune anytime in spring and summer, but try to complete it four to six weeks before the first frost. This allows the cut to heal and prevents winter damage. If your plant is too big, you can cut it back by one third at a time, then wait two to three months before pruning again. To create a bushier plant for cooking, trim one or two inches off each branch. Keep the trimmed ends for propagating new plants or to use in cooking.
The most common disease encountered by rosemary growers is powdery mildew. It appears as a white powder on the leaves and is usually found on indoor plants when humidity is high and air circulation is poor. Avoid placing your plant in bathrooms or kitchens. If powdery mildew has taken hold, try treating it with a baking soda solution or a fungicide spray.
Aphids, whiteflies, and spittlebugs are the most common pests found on rosemary. Spittlebugs don't cause much damage and can be easily removed with a spray of water. Aphids and whiteflies tend to gather in groups on the undersides of leaves. You can wash these bugs off with water, too, although you may need to use insecticidal soap to banish them for good.
If rosemary is grown in the right conditions outdoors, it's perfectly happy without fertilizer. However, plants in containers will appreciate a little non-acidic fertilizer through the spring and summer months. Provided you give rosemary plenty of sunlight, good drainage, and freely circulating air, your plant should be healthy and fuss-free.