Osmanthus Fragrans ‘Zhuang Yuan Hong’: A Vibrant Evergreen Beauty

Osmanthus Fragrans ‘Zhuang Yuan Hong’ is an evergreen shrub or small tree with a dense, spherical crown. It boasts a strong branching capacity, vigorous growth, large flowers, and abundant blooms.

During its flowering season, the blossoms are a deep orange-red color, giving the plant a high ornamental value. ‘Zhuang Yuan Hong’ is a prized and valuable variety among osmanthus plants, offering significant developmental value and socio-economic benefits.

It is ideally suited for cultivation in parks, scenic areas, residential courtyards, and makes for excellent pot plants in northern regions.

I. Basic Introduction

Osmanthus Fragrans ‘Zhuang Yuan Hong’ is an evergreen shrub or small tree. It has a spherical crown and numerous branches, resulting in a full interior. The bark is dark gray with round pores in moderate quantity.

The leaves are opposite, simple, and leathery, with entire margins and glandular points on both surfaces; they possess a petiole. The flowers are bisexual, dioecious or monoecious, and bisexual.

They grow in clusters in the leaf axils or in short terminal corymbs. The calyx is bell-shaped and 4-lobed; the corolla is orange-red, bell-shaped, with 4 lobes arranged in an imbricate pattern during bud stage.

There are 2 stamens, attached to the upper part of the corolla tube, with anthers often extended into a small point.

The ovary is 2-chambered, each chamber containing 2 pendulous ovules, the style is longer or shorter than the ovary, the stigma is capitate or 2-lobed, the sterile pistil is fusiform or conical.

The fruit is a drupe, oval or oblique oval, with a hard or bony endocarp, usually containing one seed; the endosperm is fleshy; the cotyledons are flat; the radicle is upward. The basic chromosome number is X=23.

II. Morphology and Characteristics

‘Zhuang Yuan Hong’ is an evergreen shrub or small tree with a spherical crown and numerous branches, resulting in a full internal structure. The bark is dark gray with round pores in moderate quantity.

The average number of branches in a standard plant is 5.6, the average length of spring shoots is 16.0 cm, and the average number of nodes is 7.0 nodes/shoot.

The average number of axillary buds is 30.4 buds/shoot, of which 4 buds are borne on one side of each node at a rate of 350%. Its growth indicators rank among the top in Osmanthus Dan Gui varieties.

The leaves are dark green or blackish green; hard, thick, and glossy; lanceolate to elongated oval, with an average leaf length of 11.5 cm, an average leaf width of 3.3 cm, and a length-to-width ratio of about 3.3.

The leaf surface is relatively flat, the leaf margin is recurved, with 9-11 pairs of lateral veins, and the reticulate veins are more apparent on both surfaces; the leaf tip is short-pointed to long-pointed and recurved, the leaf base is cuneate; the average petiole length is 1.0 cm.

The corolla is almost flat, the lobes are nearly round and slightly incurved; the flower color is orange-red, with an international color card number of 30C (deep orange-red).

The flower color is the most vibrant among the Osmanthus Dan Gui varieties; the flowers are fragrant and do not bear fruit after flowering.

The flowering period is from late September to early October.

III. Living Habits

The ‘Zhuangyuan Red’ requires the same cultivation environment as the distant relative Osmanthus, needing a warm, humid climate and loose, fertile, slightly acidic soil.

The National Forestry Bureau suggests that the suitable planting range for this variety is below 500 meters above sea level in the Yangtze River basin, with a pH of 5.5-6.5, in regions with deep, fertile soil.

IV. Cultivation Method

The ‘Zhuangyuan Red’ reproduces through cuttings. However, the average survival rate of cuttings is around 60%. To accelerate the reproduction of this variety, it’s advisable to graft the ‘Zhuangyuan Red’ onto a rootstock of Osmanthus.

Cutting

Cutting should be done before budding in the spring, using one-year-old branches as cuttings. The cuttings are inserted into pure sand or peat soil, covered with plastic film, and placed in a shaded area for maintenance. They can take root after the start of autumn.

1. Cutting Time. The most suitable period is from mid-May to late June (for autumn cuttings, it’s from mid-August to late September). Some regions believe that Osmanthus sprouts new shoots early in spring, so cuttings can be made in April. However, even though the cuttings have a high degree of lignification at this time, both air and soil temperatures are quite low, making it difficult for cuttings to take root and prone to decay.
   
2. Selection and Treatment of Cuttings. Use the tender shoots that sprouted in the current year for cuttings. To ensure that the cuttings are robust and full, the mother tree must be managed with fertilization and watering in winter. Fertilize with quick-acting fertilizer 2-3 times one to two months before cutting to promote growth. If the spring is dry, pay attention to watering. Cuttings that are full and well-nourished form the original root body more easily, take root quickly, and have a high survival rate, while weak branches do the opposite. The cuttings should be 8-10 cm long. The cuttings, once cut, should be quickly placed in a cool, ventilated indoor area and promptly sprayed with misty water to moisten the leaf surface and keep the cutting fresh. When trimming the cuttings, keep 5-6 top leaves. To avoid overcrowding during insertion and to prevent leaf interlocking, you can cut the leaves in half.
   
3. Insert half of the cutting into the soil with a plant spacing of 6×10 cm, and plant 200 cuttings per square meter. If the cuttings are removed after rooting, treating the cutting bed as a transitional phase, the density can be increased to make full use of the plastic greenhouse. The regenerative capacity of the osmanthus’ nutritional organs is the physiological basis for its propagation by cuttings. Osmanthus cuttings first form the primordia of roots before rooting, and then grow adventitious roots. The rooting of the cuttings is not concentrated in the healing tissue area, but on the nodes, with a few in the cortical area between the nodes. According to observations, on average, each plant produces 19 lateral roots, 13 of which root on the nodes, and 6 root in the cortical area between the nodes. If there are two nodes rooting, the lower node roots more than the upper one. As observed externally, like other tree species, osmanthus also forms healing tissue. The healing tissue is located at the end of the cuttings, forming a tumorous protrusion between the cortex and the xylem, which forms 15-20 days after insertion. If not treated with naphthaleneacetic acid, the formation of healing tissue may be delayed. After about 7-10 days of the formation of the healing tissue, new roots begin to grow.

Grafting

The rootstock for grafting osmanthus trees is generally privet or wax myrtle, often using methods such as side grafting, approach grafting, or whip-and-tongue grafting. The whip-and-tongue method is simple to perform, with a survival rate of around 93%.

The specific method is as follows: before the spring buds sprout, take a robust one-year-old branch from the parent tree, trim some leaves, and store it in cool, damp sand until the rootstock sprouts for grafting.

During grafting, first cut the rootstock about 10 centimeters from the ground, select a smooth surface and cut the bark into a “II” shape, about 2-3 centimeters long and 3-4 millimeters wide.

Peel open the “II” area of the bark, then insert the unevenly sharpened graft into the “II” area of the rootstock and wrap it with a film strip. When the new graft shoot grows to 10-15 centimeters long, cut off all the budding branches on the rootstock.

From June to August, pay attention to drought resistance, fertilization, and weed control. Potted osmanthus can be grafted using the approach method.

First, keep the rootstock alive in the pot, and during the rainy season in June and July, choose a two-year-old osmanthus branch of similar thickness to the rootstock for grafting in the pot.

After the graft survives, cut it off before the “White Dew” period to form a new plant, which can bloom within the year.

V. Value and Others

Main Value

The ‘Zhuangyuan Red’ has a dense crown, good shape, strong branching power, large growth volume, large flowers, many flowers, and bright red color, making it extremely valuable for ornamental purposes.

It’s very suitable for planting in park attractions and community courtyards, and it also makes a good pot plant in northern regions.