Joseph Masabni and Stephen King Assistant Professor and Extension Horticulturist, and former Associate Professor, Texas A&M Department of Horticultural Sciences; The Texas A&M University System
Rosemary (Rosmarinus officinalis) is relatively easy to grow, making it a good choice for any home herb garden. Its pungent flavor and pinelike scent make rosemary a popular ingredient in foods. The upright varieties are best for both fresh and dried use.
Rosemary can be grown as an annual (completes its life cycle in 1 year) or a perennial (completes its life cycle in 3 or more years). In herb gardens, it is often planted along with thyme, oregano, sage, and lavender. When planting, choose a variety that is suitable to the climate, soil, and desired use.
These varieties are best for Texas:
- Blue Boy
- Dancing Waters
- Golden Rai
- Pine Scented
- Spice Islands
- White Pine
Scented rosemary is best for cooking because of its excellent flavor and soft leaves. Blue Boy, Spice Islands, and White rosemary are also used in cooking. Arp, Dancing Waters, Golden Rain, Pink, and White varieties are more often used as landscape plants.
Rosemary can be grown in pots or in an herb garden (Fig. 1). 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.
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 http://soiltesting. tamu.edu/. 3. If needed, fertilize according to the soil 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 surface and incorporate it with a pitch fork or a rototiller to a depth of 6 to 8 inches. Raised or slightly mounded beds provide the best drainage for the herb.
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 1½ 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° and 70°F.
- After about 8 weeks, the cuttings will be rooted and ready for transplanting to their permanent location.
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 allpurpose fertilizer in dry or liquid form is suitable as long as it is applied correctly. To prevent leaf burning, avoid applying fertilizer directly onto the plant.
Too much water can cause root rot. Sometimes it can be difficult to determine when a rosemary plant needs water because its needles do not wilt as broad leaves do. 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.
Although rosemary resists most diseases, some cases of powdery mildew have been reported. To prevent the 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 the plants. Pruning also stimulates them to produce new shoots.
Rosemary is fairly resistant to pests. If spider mites, mealy bugs, or scales do appear, any organic or inorganic insecticide may be used.
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.
Once the plant grows to a suitable size, you can pick several small branches without harming it. Nursery plants can be harvested sooner than cuttings or seeds (Table 1).
Rosemary plants can be harvested several times in a season, but they should be allowed to replace their growth between harvests. Some varieties are valued for their small flowers, which are harvested for use in salads.
The clippings can be used fresh or dried for later use (Fig. 2). Fresh cuttings will retain their best flavor for 2 to 7 days in the refrigerator. To store rosemary for longer periods, hang it in bundles to dry.
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