Rosemary (Rosmarinus officinalis) is an evergreen shrub that is native to the Mediterranean region. It is relatively easy to grow, making it a good choice for any low- maintenance landscapes or home herb gardens.
The small, linear leaves are arranged on opposite sides of the stems. The leaves are rich in essential oils, and their pungent flavor and pine-like scent make them a popular ingredient in foods.
The shrub bears small, tubular flowers (Fig. 1) that can be white (‘Albus’), pink (‘Roseus’), blue (‘Tuscan Blue’), or any shade in between. The flowers are borne on the upper leaf axils (the angle between the stem and the top of the leaves) in spring, summer, and fall. They can be used in salads and as a rosemary-flavored garnish.
The growth habit ranges from very upright (‘Fastigiatus’) to spreading and prostrate (‘Prostratus’, Fig. 2). The upright varieties are best for both fresh and dried use.
Rosemary is a perennial (completes its life cycle in 3 or more years) in most areas in Texas (USDA Cold Hardiness Zone 7 and warmer). In herb gardens, it is often planted with thyme, oregano, sage, and lavender. When planting, choose a variety that is suitable for the climate, soil, and desired use.
Varieties
These varieties are best for Texas:
- ‘Albus’
- ‘Arp’
- ‘Blue Boy’
- ‘Dancing Waters’
- ‘Golden Rain’
- ‘Pine Scented’
- ‘Prostratus’
- ‘Roseus’
- ‘Spice Islands’
The best variety for cooking is ‘Pine Scented’ because of its excellent flavor and soft leaves. Also used in cooking are ‘Blue Boy,’ ‘Spice Islands,’ and ‘White’ rosemary. The varieties used more often as landscape plants are ‘Arp,’ ‘Dancing Waters,’ ‘Golden Rain,’ ‘Pink,’ and ‘White’.
Site Selection
Rosemary can grow in pots or herb gardens (Fig. 3). Most varieties grow best in well- drained, loamy, slightly acidic soil. The preferred soil pH is between 6.0 and 7.0.
Rosemary should receive at least 6 hours of sun each day; it grows best in full sun. If you plan to use rosemary as a perennial plant, choose a site that will not be disturbed by tilling.
Soil Preparation
Follow these steps to prepare the soil:
- Remove all rocks, shrubs, weeds, plant debris, and tree roots from the area to be planted.
- Collect a soil sample and have it analyzed to determine your soil’s fertility level. For information about the Texas A&M Soil, Water and Forage Testing Laboratory, visit https://soiltesting.tamu.edu/.
- If needed, fertilize the soil according to the test results to supplement the nutrition added from compost or organic matter. If the pH is too low, add lime to make the soil more alkaline.
- Add about 4 inches of organic matter or compost to the soil surface and incorporate it with a pitchfork or a rototiller to a depth of 4 to 6 inches. Raised or slightly mounded beds provide the best drainage for this herb.
Planting
Like most herbs, rosemary is fairly drought resistant and, if healthy enough, can tolerate a light freeze.
It is most successful when grown from cuttings or transplants. Although seed is readily available and usually inexpensive, its germination rate is usually only about 15 percent.
The best way to propagate rosemary is by taking a cutting from an already vigorous plant:
- Clip a 3-inch branch from the stem of the plant.
- Trim off most of the lower leaves to 1-½ inches up the stem.
- Plant one or two cuttings into a 3-inch pot.
- Water the cuttings.
- Place the pot in a windowsill with indirect sunlight and temperatures between 60°F and 70°F.
- After about 8 weeks, the cuttings will be rooted and ready for transplanting to their permanent location.
Fertilizing
Rosemary seldom needs fertilizer. But if growth is slow or the plant appears stunted or pale yellow, apply fertilizer once in early spring before new growth appears.
Any all-purpose fertilizer in dry or liquid form is suitable as long as you apply it correctly. To prevent leaf burning, do not apply it directly to the plant.
Watering
Too much water can cause root rot. Because its needles do not wilt as broad leaves do, sometimes it can be difficult to determine when a rosemary plant needs water. On average, water rosemary every 1 to 2 weeks, depending on the plant size and climate conditions.
Allow the plants to dry out thoroughly between each watering.
Diseases
Although rosemary resists most diseases, some cases of powdery mildew have been reported. Other possible diseases include aerial blight, bacterial leaf spots, and root rots.
To prevent a disease from spreading, check the plants regularly and apply the proper fungicides when needed. You can reduce the incidence of diseases by pruning overgrown plants to improve air circulation within them. Pruning also stimulates the production of new shoots.
Insects
Rosemary is fairly resistant to pests. If spider mites, mealy bugs, or scales do appear, you may use any organic or inorganic insecticide that is labeled to treat them.
If the plant has scales, an easy solution is to clip off and discard the infested plant tips; scales are sedentary insects. For mealy bugs, spray the plants with water, pyrethrum soap, or a soap-based insecticide.
Insects that suck plant sap are generally more prevalent in areas where too much nitrogen fertilizer has been applied. You can avoid most insect problems by fertilizing properly.
Harvesting
Once the plant grows to a suitable size, you can pick several small branches without harming it. Nursery plants can be harvested sooner than can cuttings or seeds (Table 1).
Although you may harvest rosemary several times in a season, allow the plants to replace their growth between harvests.
The clippings can be used fresh or dried for later use (Fig. 4). Fresh cuttings retain their best flavor for 2 to 7 days in the refrigerator. To store rosemary longer, hang it in bundles to dry.
Acknowledgement
M’Kensie Aday and Stephen King contributed to the manuscript for an earlier version of this publication.
