Detailed Explanation of the Key Technical Points for Growing Rosemary
Rosemary is a valuable natural aromatic plant that gives off a fresh scent during the growing season and has the effect of refreshing the mind and lifting the spirits. Its stems, leaves and flowers have a pleasant fragrance, and the aromatic oil extracted from the flowers and tender branches can be used to blend air fresheners, perfumes, soaps and other cosmetic ingredients, giving it extremely high cultivation value. Let us take a look below at rosemary cultivation techniques!
Growth Habits of Rosemary
Rosemary is native to Europe and the Mediterranean coast of North Africa, and in southern Europe it is mainly grown as a cash crop. It was introduced to China during the Cao Wei period, and is now mainly cultivated in most parts of the south and in the Shandong region. It prefers a warm climate, but grows slowly during the high-temperature period on the plains of Taiwan, China; temperatures without cold waves in winter are more suitable for its growth. As for water supply, since rosemary leaves are leathery, it is fairly drought-tolerant, so soil rich in sand that drains well is more conducive to its growth and development. It is worth noting that rosemary grows slowly, so its ability to regenerate is not strong.
Propagation Techniques for Rosemary
1. Sowing: Seedlings are generally raised in a greenhouse in early spring. Either traditional soil-based seedling raising or plug-tray seedling raising can be used, but the germination rate is very low, generally only 10-20%, and in the first year rosemary grows extremely slowly. Even by autumn the plants are not much larger than when they were just transplanted, and it takes 2-3 years to form a large yield, which is very slow. Therefore, vegetative propagation is generally used in production. However, plants grown from seed have a more fragrant scent, so which propagation method to use depends on the need.
2. Cuttings: Rosemary cutting propagation is mostly carried out from winter to early spring. Select fresh, healthy stems that have not yet fully lignified as cuttings, cut them about 10-15 cm from the top, remove about 1/3 of the leaves from the lower part of the branch, and insert them directly into the medium. Keep the medium moist; roots will form in about 3-4 weeks, and after 7 weeks they can be transplanted to open ground. The minimum night temperature for cuttings is 13°C.
3. Layering: Rosemary layering propagation mainly makes use of the characteristic that rosemary stems can produce adventitious roots. Bend a branch close to the ground, cover it with soil, and leave the top exposed to the air. Once new roots have grown, cut it from the parent plant to form a new individual, then transplant it to open ground.
Rosemary Cultivation Techniques
1. Land preparation: Before transplanting rosemary, first dig holes in the leveled land according to the row and plant spacing, apply a small amount of base fertilizer, then cover the base fertilizer with a thin layer of soil, and it is ready for transplanting. Usually the seedlings transplanted in the field are mother seedlings that have taken root and survived from cuttings. The transplanting spacing is 40×40 cm, and the number planted per mu is 4000-4300 plants. In central and southern Yunnan Province, planting can be done in all four seasons, with spring and autumn being the best.
2. Planting: For rosemary planting, it is best to choose cloudy days, rainy days, or early morning and evening when the sunlight is not strong. After transplanting, water thoroughly to settle the roots. When watering, do not let the seedlings topple over; if any fall over, straighten and firm them promptly. Water rosemary a second time 5 days after planting (depending on whether the soil is dry or moist). Once the seedlings have survived, watering can be reduced. Replace dead seedlings promptly. When planting, line up the holes in straight lines using the centers of the holes as points, to facilitate ventilation.
3. Fertilization: Rosemary is fairly tolerant of poor soil. During the seedling stage, according to different soil conditions, apply a small amount of compound fertilizer after cultivating and weeding. After fertilizing, cover the fertilizer with soil. After each harvest, apply a quick-acting fertilizer as a top dressing, mainly nitrogen and phosphorus fertilizer. Generally, apply 15 kg of urea and 25 kg of ordinary superphosphate per mu.
4. Pruning: Rosemary can be pruned 3 months after planting and surviving. Excessive heavy pruning often causes the plant to be unable to sprout again. A relatively safe practice is not to cut more than half the length of the branch each time you prune. Although small buds appear at every leaf axil of the rosemary plant, and as the branches extend these axillary buds will also develop into branches, after they grow the whole plant becomes messy due to branches growing sideways, and poor ventilation also makes it prone to pest and disease damage. Therefore, regular pruning and shaping are very important.
5. Harvesting: Rosemary can be harvested for many years after a single planting. Harvesting is mainly for branches and leaves, which can be cut with scissors or picked directly by hand. However, special attention must be paid because the sap flowing from the wounds quickly turns into a sticky gum that is very difficult to remove, so gloves and long-sleeved clothing must be worn during harvesting. The number of harvests depends on the growth situation; generally it can be harvested 3-4 times per year, with at least 250-350 kg per mu each time.
6. Pests and diseases: In humid environments, root rot, gray mold and other diseases are common on rosemary. If the plant wilts while the growing medium is still moist, the plant needs to be moved out of the greenhouse immediately. The most common pests are red spider mites and whiteflies, and the most ideal method is biological control. Emphasis should be placed on prevention, starting with sanitation, proper water management, reasonable temperature and light, and frequent observation to promptly remove diseased and weak plants.