A Detailed Guide to Flower Propagation Techniques: Master Several Common Methods with Ease

There are many propagation methods for flowers. Below are several methods for growers of flowers to choose from as appropriate.

I. Seed Propagation Method

Ordinary flower seeds, such as those of wax begonia (Begonia semperflorens) and garden balsam (Impatiens balsamina), can be sown directly without any treatment. Seeds with an oily or waxy coat, such as those of Yulan magnolia (Magnolia denudata), can be mixed with wood ash made into a paste with water before sowing. Lotus and canna have harder seed coats, so before sowing the seed coat must be scraped and the seeds soaked in warm water for 24 hours. Seeds of elm-leaved spirea (Prunus triloba), if sown in early spring, can germinate in spring. Before sowing, all kinds of seeds need a germination test to check the germination rate, so as to determine the sowing rate. For herbaceous flowers with thicker seed coats, germination is usually accelerated before spring sowing, so as to achieve fast and uniform emergence and a high rate of seedling establishment. Acceleration is mostly done by water soaking and stratification.

1. Water soaking to accelerate germination. It can be divided into 3 water temperature treatments. First, cold water soaking to accelerate germination, water temperature above 0°C, suitable for seeds with thinner seed coats, such as Chinese wisteria (Wisteria sinensis), palm, wintersweet (Chimonanthus praecox) and cedar; second, warm water soaking to accelerate germination, water temperature 40-60°C, suitable for seeds with thicker seed coats such as tree peony (Paeonia suffruticosa), Chinese peony (Paeonia lactiflora), redbud (Cercis chinensis), Chinese wingnut (Pterocarya stenoptera), Chinese scholar tree (Sophora japonica), Chinese arborvitae (Platycladus orientalis) and golden larch (Pseudolarix amabilis); third, hot water soaking to accelerate germination, water temperature 70-90°C, suitable for seeds with hard seed coats, such as silk tree (Albizia julibrissin), black locust (Robinia pseudoacacia) and camphor tree (Cinnamomum camphora). When soaking seeds, use 3 times as much water as seeds, and stir when pouring in the water so that the seeds are heated evenly. When soaking with hot water, once the water temperature drops to natural temperature, stop stirring, then soak for 1-3 days; after the seeds absorb water and swell, take them out and accelerate germination at 18-25°C. During acceleration, rinse with warm water 1-2 times a day, and take care to turn them gently; once the seeds split open, they can be sown.

2. Stratification to accelerate germination. Stratification to accelerate germination is done by mixing 3 parts wet sand with 1 part seeds, then keeping them moist and cold at 0-7°C. This method is suitable for seeds of southern magnolia (Magnolia grandiflora), banana shrub (Michelia figo), white magnolia (Magnolia denudata), the honeysuckle family and flowers that can germinate the following year.

In addition, for seeds with long dormancy or seeds that sprout the following year, such as osmanthus (Osmanthus fragrans), holly and coral tree, a variable temperature method of accelerating germination can also be used: after soaking, keep the temperature at 25-30°C during the day and about 15°C at night, repeating for about 10-20 days, and germination can be achieved.

II. Division Propagation Method

Separating small plants from the mother plant, or separating bulbs and corms from the mother body, and planting them separately to form independent new plants is called division propagation. This method is divided into two types: division of clumps and division of bulbs.

1. Division of clumps. The root suckers, stem suckers and rhizomes produced on the mother plant are separated and grown into independent new shoots. The time for division propagation depends on the flower variety; usually those that bloom in spring are divided in the renewal season, and those that bloom in autumn are divided in spring. Autumn division should be carried out when the aboveground part has entered dormancy and the underground part is still active, such as for tree peony and Chinese peony; spring division should be carried out before germination, such as for fragrant plantain lily (Hosta plantaginea) and iris. When dividing, for perennial flowers, first remove the old soil attached to the roots, then use a sharp knife to separate them along the natural gaps, following the direction, so that each small clump after division has at least 2-3 buds. When dividing woody flowers, there is no need to knock the soil off the mother plant; a flower trowel can be used to dig away the soil and dig out the young plant from one side of the root crown for planting. When dividing, injure the roots as little as possible to help survival.

2. Division of bulbs. This method is mainly used for the propagation of bulbous and cormous flowers. The time for dividing bulbs is after dormancy; the bulbs and corms are separated and dug out from the mother bulb and grown into independent new plants. For example, the small bulbs of hyacinth usually form around the base at 4 weeks; after separation from the mother bulb and growing for 4 years, they can reach the same size as the mother plant. Small narcissus bulbs can grow into large bulbs after 3 years. A large tulip bulb forms 2-3 small bulbs after 1 year, and the small bulbs can grow into large bulbs after 1-2 years of growth. A gladiolus corm can form 1-4 large corms after 1 year of growth and can produce many small corms.

III. Grafting Propagation Method. Grafting is the artificial joining of the branch or bud of the flower plant to be grown onto the stem or root of another flower plant. Grafting is divided into two major categories: branch grafting and bud grafting. This method can not only maintain the characteristics of the original variety, but also improve resistance to adverse environmental conditions, and can regulate the growth and development process of flowers and trees, which is conducive to earlier flowering and fruiting. This method is mostly used for herbaceous flowers, and a small number of woody flowers can also use this method. The key to successful grafting: first, control the grafting time; it should usually be done when the sap begins to flow and the buds have not yet sprouted. Branch grafting is mostly in early spring from March to April, and bud grafting is mostly in July to August. Second, the scion and rootstock should be selected from plants with a close genetic relationship and compatibility, such as using privet of the same family as the rootstock to graft osmanthus or lilac. Third, the rootstock should preferably be a vigorously growing 1-2 year old seedling or a 1-year-old cutting seedling; if the rootstock is too old, it will affect survival. The scion should be selected from high-quality, robust and mature 1-year-old branches. Fourth, when grafting, note that the rootstock is cut first and then the scion (to shorten the water evaporation time); the tools must be sharp, the cuts must be smooth, the cambium must be aligned during grafting, the parenchyma cells must be pressed close, the joint must be tightly fitted, and the tying should be moderately tight. Fifth, check promptly after grafting; for plants that have successfully taken, remove the binding material in time. If the mound soil method is used for grafting, once new buds sprout, remove the soil mound immediately, so as to prevent the young buds from turning yellow because they cannot see sunlight.