Mountainous Bulb Propagation and Cultivation Techniques for Oriental Lilies

In recent years, both the cut flower production and consumption of lilies in China have grown rapidly, yet the bulbs still depend almost entirely on imports, and bulb self-sufficiency has become a "bottleneck" restricting China's lily cut flower production. Achieving domestic production of high-quality commercial lily bulbs is imperative. Zhejiang Province has diverse landform types, and the temperature differences at different altitudes are highly beneficial for bulb swelling and development and flower bud differentiation in bulbous flowers. Selecting cool mountainous areas in Zhejiang Province for cultivation, carrying out purification and rejuvenation and bulblet propagation of lilies, and solving the long-standing problem of China's inability to achieve self-sufficiency in lily bulbs has far-reaching significance for the development of the lily cut flower industry.

1. Mountainous Propagation and Cultivation Techniques for Oriental Lilies

1.1 Varieties

The main Oriental lily varieties that sell well on the market include Siberia, Sorbonne, Marcopolo, Acapulco and Tiber. Bulblets with a circumference of 6-9 cm are selected for propagation. Lily bulblets can be obtained through direct import or self-propagation. Because the Netherlands has restricted the export of bulblets in recent years, large-scale scale cutting propagation using film-mulched field planting and full-substrate temperature and humidity control technology has yielded large quantities of high-quality Oriental lily bulblets. To promote new root growth and disinfect the bulblets, seeds are soaked in a mixed solution of fungicide and hormone before planting.

1.2 Plot Selection and Preparation

To ensure that lily plants safely overwinter the summer and have the longest possible annual growth period, mountainous conditions at an altitude of 800-1000 m must be selected. Lilies are sensitive to continuous cropping and highly sensitive to soil salinity, so new land must be chosen for planting. Before planting, deep plow 30 cm, with a bed height of at least 25 cm, a bed width of about 1.1 m, and paths of 50-60 cm. Before planting, the soil should be thoroughly loosened, with a moisture content of about 60%. Lilies prefer organic fertilizer, and 2000-3000 kg of fully decomposed compost, cow manure and other organic fertilizers should be applied per mu. To promote rapid bulblet development, additional phosphorus and potassium fertilizers such as bone meal, calcium magnesium phosphate and superphosphate should be applied. The required nitrogen, phosphorus and potassium ratio for lilies should be 5:10:10.

1.3 Mountainous Planting Parameters

Lily bulblets can be planted in spring from February to April, or in autumn from September to November, but transplanting after temperatures rise in late spring is most taboo, otherwise the survival rate decreases. When the supply of bulblets permits, autumn planting is preferable. In 2003, the planting time in the mountainous area of Dayang Town, Jinyun County was from April 15 to April 28; in 2004, the planting time in the mountainous area of Gaoping Township, Suichang County was from March 20 to April 12.

The planting density of lilies varies with variety and bulb size. For Oriental lily bulblets of 6-9 cm specification, 15,000-18,000 can be planted per mu, with a plant spacing of 8-10 cm and a row spacing of 20-25 cm. To prevent surface soil crusting, autumn-planted lilies should be covered with straw or peat soil on the surface. Lilies have fleshy contractile roots, so planting depth should be somewhat deeper. Generally, the distance from the top of the bulb to the soil surface is 6-12 cm, and larger bulbs should be planted appropriately deeper.

1.4 Mountainous Cultivation Management Techniques

Watering: Lilies grow rapidly when spring arrives. At this time, the number of irrigations is determined according to weather conditions, mainly by watering or sprinkler irrigation, and furrow irrigation should be used as little as possible. Watering should be done in the morning and evening. During high summer temperatures, water demand is high, so watering should be done before 10:00 in the morning, and appropriate foliar water spraying can be combined to ensure water supply.

Fertilization: From May to June, apply 2-3 times of thin liquid fertilizers such as cake fertilizer water. Nitrogen application is mainly to ensure thick and strong stem growth in the middle and late stages of lily growth, but to avoid leaf burn from nitrogen fertilizer, the plants should be rinsed with clean water after nitrogen application. To improve stem strength, apply 1-2 additional applications of phosphorus and potassium fertilizers such as superphosphate and plant ash. Fertilization should be kept away from the stem base, and imported compound fertilizer granules can also be applied in bands, with better results especially after rain. Stop fertilizing during high summer temperatures, continue using phosphorus and potassium fertilizers after the Beginning of Autumn, and apply 1-2 additional applications of calcium nitrate at a standard of 1 kg calcium nitrate per 100 sq cm, or spray at a concentration of 0.2%-0.3%.

Weeding: In bulb propagation and cultivation, this requires a large amount of labor. Weeding between furrows must be carried out regularly, combined with intertillage, to remove young weeds in time and prevent weed coverage. After the Beginning of Autumn, lily plants have formed a closed canopy, so hoeing should be avoided as much as possible to prevent root damage.

Flower Removal: To ensure that nutrients are concentrated for lily bulb development, flowers must be removed in time. Flowers should be removed when the flower buds are obviously swollen; too early or too late is unsuitable. Note that this should be done around noon on sunny days, as removing flowers on cloudy and rainy days can easily cause pathogen infection of the wounds.

Pest and Disease Control: Due to the hot and rainy weather in Zhejiang, lily plants are highly susceptible to gray mold (Botrytis cinerea). To ensure high quality and high yield in lily bulb propagation, 50% carbendazim 600x solution or 75% chlorothalonil 800x solution must be sprayed promptly after rain for control, and diseased leaves and plants should be removed in time.

1.5 Bulb Harvest and Handling

Timely Harvesting: Lily bulbs should not be harvested too early (bulbs undergo after-ripening) or too late (to prevent bulbs from freezing). Because temperatures in mountainous areas begin to drop in late October, bulb harvesting usually starts in mid-to-late October and ends before mid-November. Manual harvesting is used: first loosen the soil and then lift the bulbs, taking care not to damage the bulbs.

Cleaning and Disinfection: Place lily bulbs in flat baskets and rinse with clean water to remove attached mud and small sand and stones, making the bulb surface white and clean. Soak the cleaned bulbs together with the crates in a disinfection pool for about 20 minutes. A disinfectant solution of 600x carbendazim and 1000x iprodione gives better results. After removing the bulb crates from the disinfectant solution, dry them with a blower or leave them to fully drain the water from the bulb surface, then carry out grading and packaging.

Grading and Packaging: Using self-made sizing rings, grade the bulbs into 3 specifications: 12-14 cm, 14-16 cm, and 16-18 cm and above. When packing, use imported peat as the substrate, or place fillers such as Northeast peat or crushed wood shavings (fresh wood shavings must be used) together with the bulbs in plastic crates, and wrap with film to retain moisture. Moderate moisture is required, with the water content in the substrate preferably 40%-45%; too wet can easily cause the bulbs to rot in the crates. Packaging specifications are: 200 bulbs per crate for the 16-18 cm specification, 300 bulbs per crate for the 14-16 cm specification, and 400 bulbs per crate for the 12-14 cm specification.

After grading and packaging, lily bulbs are first pre-cooled at 13-15°C for 2 weeks, then placed at 2°C for 8 weeks for low-temperature dormancy breaking treatment, and finally stored long-term in a warehouse at minus 1.5 to minus 2°C.

2. Results of Self-Propagation of Mountainous Lily Bulbs

2.1 Bulb Quality and Leaf Number

To monitor the quality of self-propagated lily bulbs in a timely manner, we conducted analytical research on the relationship between plant leaf number and bulb quality. Taking the Oriental lily variety Sorbonne as an example, lily plants in the same planting area were divided into 4 groups according to leaf number: fewer than 15 leaves, 15-17 leaves, 18-20 leaves, and more than 20 leaves. Plants were dug up on September 25, October 11 and November 15, and their bulb morphological indicators were measured.

The experimental results showed that with increasing leaf number, lily plant height and harvested bulb fresh weight and circumference all increased significantly. There was no significant difference among leaf-number groups on September 25, while there were significant differences among separated groups. The leaf number of lily plants had a strong correlation with bulb circumference, fresh weight and lily plant height. For example, plants with 18-20 or more leaves could all yield bulbs with a circumference of 16-18 cm. Therefore, leaf number can be used to gauge the underground growth of the plant and the size of the bulbs to be harvested in the future, which has strong practical value.

2.2 Bulb Formation Rate of Mountainous Bulbs

Using mountainous areas in Zhejiang Province for Oriental lily bulb propagation, after 1 year of cultivation, the commercial bulb formation rate (greater than 12 cm) reached 71.7%, among which the average bulb formation rate of large-specification bulbs (16-18 cm and above) reached 15.4%, showing that the effect of mountainous propagation is good.

When cultivated in the mountains of Zhejiang Province, different varieties of Oriental lilies also differ in bulb formation rate for different specifications. For example, the large-specification bulb formation rate of Sorbonne is higher than that of Siberia.

2.3 Nutrient Comparison Between Domestic and Imported Bulbs

To more accurately evaluate the quality of self-propagated lily bulbs, samples were taken at harvest time to determine the starch, soluble sugar and sucrose contents in the bulbs and compare them with the nutrient contents of imported bulbs. It was found that the starch content of domestic bulbs was similar to that of imported bulbs, and the quality reached the requirements for commercial bulbs. The soluble sugar content in domestic bulbs was slightly lower than in imported bulbs, but the sucrose content was similar to that of imported bulbs. Lanzhou lily had higher soluble sugar and sucrose contents, with sufficient sugar content, giving it a better taste as an edible lily.

However, at present, because postharvest dormancy breaking treatment and low-temperature storage technology have not yet been mastered, nutrient content drops substantially during postharvest handling and storage of bulbs after harvest, making it difficult to guarantee the quality of commercial bulbs, and the quality of cut flower production is also clearly affected.

2.4 Production Cost Comparison Between Domestic and Imported Bulbs

According to an estimate of the production cost of Oriental lily bulbs propagated in the mountains of Zhejiang Province, based on an average bulb formation rate of 72%, the production cost per harvested lily bulb is 0.33 yuan. That is, the bulb production cost using self-propagated bulblets is 0.51 yuan per bulb, while the bulb production cost using imported bulblets is 0.91 yuan per bulb. At present, the production cost of lily bulbs in the Netherlands is about 0.12-0.15 euros, equivalent to 1.2-1.5 yuan per bulb. Therefore, domestic lily bulbs have a considerably low production cost and a very strong price advantage.

3. Summary

Production practice in recent years has shown that by adopting high-mountain self-propagation bulb production technology, optimizing planting parameters, and combining flower removal and formula fertilization treatments, production costs are reduced, and a technical system for domestic propagation of Oriental lily bulbs has basically been established. However, issues such as the domestication of germplasm sources and bulb virus elimination technology mean that the autonomy and quality of germplasm sources cannot be guaranteed. Zhejiang's mountainous areas are rich in climatic resources and relatively suitable for bulb propagation, but because spring rainfall is excessive and summer is hot and rainy, lily gray mold often occurs severely, affecting bulb quality. In addition, mountain soils often have strong sandiness and poor fertilizer retention capacity, so rational fertilization is required; viral diseases caused by continuous cropping or partial continuous cropping are also one of the problems urgently needing solution. Therefore, in the process of domestic production of lily bulbs, a series of problems still remain to be further studied and solved.