Taxonomy and distribution

M. rubra is a small to medium-sized evergreen tree species of genus Myrica, family Myricaceae, growing up to 10 m high, with smooth gray bark and a uniform spherical to hemispherical crown (Fig. 1 & 2). Branchlets and buds glabrous. Petiole 2-10 mm, glabrous to puberulent adaxially; leaf blade cuneate-obovate or narrowly elliptic-obovate, leathery, glabrous, abaxially pale green and sparsely to moderately golden glandular, adaxially dark green, base cuneate, margin entire or serrate in apical 1/2, apex obtuse to acute (Fig.3). It is usually dioecious, wind pollinated, and only a few individuals are monoecious. Male spikes are simple or inconspicuously branched, solitary or sometimes few together in leaf axils; bracts suborbicular, ca. 1 mm, glabrous but abaxially golden glandular. Male flowers with 2-4 ovate bracteoles, sparsely ciliate. Stamens 4-6; anthers dark red, ellipsoid (Fig. 4, A). Female spikes (Fig. 4, B) solitary in leaf axils, 0.5-1.5 cm, many flowered; rachis pubescent and glandular; bracts overlapping, glabrous and inconspicuously glandular. Female flowers with 4 bracteoles. Ovary velutinous; stigmas 2, bright red, slender. Drupe dark red or purple-red at maturity, globose, 1-1.5 cm in diam., to 3 cm when cultivated (Fig. 3b). M. rubra is widely distributed South-Central to Southeast mainland China, Hainan and Taiwan, Japan, Korea, Nansei-shoto, Philippines (Fig. 5). There are many local cultivars in the Zhejiang, Jiangsu, Fujian, Guangdong, and Yunnan provinces.

Cultivars

The cultivars were mostly classified on the basis of ripening date, fruit color, fruit weight, and stone characters. There are more than 300 cultivars (accessions) of M. rubra in China. But the 4 cultivars from Zhejiang province are the most popular cultivars, which are ‘Dongkui’, ‘Biqi’, ‘Dingao’, and ‘Zhoushan Wandao’. Those four cultivars accounted for 60% cultivated area. The cultivar ‘Dongkui’ alone has the cultivated area 85 000 ha and annual production 280 000 tons, which are 20% of the total area and 28% of the total production of China. ‘Dongkui’ is famous for its biggest fruits, with average single fruit weight 25g, the biggest is 52g, good quality and excellent storage capacity. The second cultivar ‘Biqi’ is well known for the fragrance rich fruit with dark color.

Bud mutation and natural elite line identification are the principle approaches for new cultivars breeding. Interspecific hybridization is also reported. Some monoecious resources are also selected and used for breeding. The monoecious plant is useful when it is cultivated alone for landscape or garden for successful fruiting.

Propagation

M. rubra can be propagated through seeds, cuttings, grafting, and tissue culture. The seed consists of a large embryo that is surrounded by a thin seed coat and a hard endocarp; like fruits, different cultivars have different size seeds (Fig. 6). Seeds of most Myrica species are dormant at maturity and require prolonged cold stratification (chilling) to break dormancy. Application of exogenous GA3 or by removal of endocarp and seed coat tissues can increase seed germination. However, seedling production by seeds is not widely adopted due to the low germination rate and genetic inconsistency.

Propagation by grafting scions from a fruiting tree is the most adopted technology for seedling production. Grafting elite scions on an old rootstock is also widely used to improve survive and decrease the time to initial fruit bearing when it is necessary to change the cultivar or to rejuvenile the tree (Fig. 7). Other vegetative propagation such as cuttings, suckers, and layering are sometimes adopted. 

Tissue culture (micropropagation) is an alternative high efficient vegetative propagation method for faster multiplication of true-to-type genotypes in the minimum possible time, especially for some new cultivar or premium selection which is lack of mother plants (Fig. 7) However, the technology may need a lot of time and efforts to develop a perfect protocol to propagate high quality plantlets. I have spend more that two years on Dongkui, and will try on more selections. It is listed on my friend's nursery website for sale, due to high temperature in summer, we want to ship in cool weather. 

Fig. 8 The in vitro rooted tissue cultured shoots (left) and plantlets with vigorous roots after transplanted into potting mix, which I spent a lot of time and efforts to develop the protocol for a new selection of Dongkui Yangmei. 

Cultivation

M. rubra are usually cultivated on hill slopes of south-eastern China. It is adapted to acidic soils (pH 4.5-6). It can form a symbiosis with the actinomycete Frankia and produce nitrogen fixing root nodules. Thus the plants have high potassium demand; the N-P-K ratio of 1-0.5-2.6 is recommended. Fertilizers usually supplied twice a year, one before sprouting in spring, the other time is just after the harvesting. During the fruiting stage, extra potassium, phosphorus, and boron are usually supplemented through foliar spray. Tree form is controlled by tipping in spring and pruning in winter. A number of pests and disease affect red bayberry, such as bayberry whitefly, Fruit fly and scale. Fungi, bacteria and nematodes all cause diseases of Chinese bayberry plants. 

Fruits harvest and postharvest.

The edible portion is comprised of many soft and succulent segments in a radial arrangement, around a single cherry stone-like seed. They contain a broad spectrum of vitamins (vitamin C, thiamine, riboflavin, carotene) and minerals. Fruit of most cultivars are 10-20 g weight and 2-3 cm diameter and bright red to almost black in color, depending upon the cultivar. The fruit ripen in China from mid-June to early July, in mid-summer. As the Chinese bayberry is typically non-climacteric and thus will not continue to ripen once removed from the tree, fruit must be harvested when they reach optimal eating quality and visual appearance. So, the harvest period is short, being just 2-3 weeks duration. And for each single cultivar, the harvest time usually only one week. As the temperature of mid-summer is very high, The farmers usually harvest the fruits in the early morning (4-8 am, even with headlight) to avoid the high field heat after sunrise to keep fruits fresh to avoid the high field heat, and can sell with a good price. The weather is usually very foggy and sometime have shower at that time. And in Zhejiang and other main producing area, Yangmei is usually cultivated on the slope of mountains. Thus it is a very tuff job sometimes dangerous to harvest the fruits from the hills (Fig. 9). The harvested fruits then will be screened or classified based on size and color right after dawn for a good marketing (Fig. 10).