The greenhouse-grown scent has distinct advantages: high quality, early market entry, premium pricing, and rapid sales. Sassafras grows free from pests and diseases, without contamination from pesticides or harmful substances, making it an ideal eco-friendly vegetable. In recent years, we have adopted plastic greenhouses for cultivating fast-growing and high-yield citron. Seedlings from open fields are transplanted into high-density greenhouses in their first or second year, then moved back to open areas during winter. This method can yield over 12,000 kg per 667 m², with income reaching 30,000 to 50,000 yuan, offering significant economic returns. The key cultivation techniques are as follows.
1. **Seedling Propagation**
Seedlings can be propagated through seeds, root cuttings, or stem and root cuttings. Due to the large volume needed for greenhouse planting, seedlings are often raised in nurseries before transplanting.
1.1 **Soil Preparation**
Choose fertile, loose soil with a deep plowed layer, good irrigation, and drainage. Apply 60-75 m³ of decomposed organic fertilizer per hectare, followed by deep plowing 30 cm. Add 750 kg of superphosphate or diammonium phosphate per hectare. Seven days before sowing, water thoroughly, and pour again after 3–5 days to maintain moisture and prevent compaction.
1.2 **Seed Treatment**
Soak seeds in 10g/kg formaldehyde solution for 20 minutes for disinfection, then rinse with water. Soak in warm water (30–40°C) while stirring until cooled to 25°C. Rinse and soak for 12 hours. After sufficient hydration, place seeds in seedling trays, maintaining a temperature of 20–25°C. After 3–4 days, when 30% of the seeds sprout, proceed with sowing.
1.3 **Sowing Methods**
Sow in open fields at temperatures of 1–5°C or 10 cm soil depth at 13°C. Greenhouse sowing can begin 20–30 days earlier. Use two methods: bottom watering and trench sowing. Sow 45–60 kg per hectare, cover with 1 cm soil. Drill rows 25–30 cm apart, 2–3 cm deep. Water after sowing and sow seeds uniformly. Cover with 1.5–2 cm soil, using 22.5–30 kg per hectare.
1.4 **Seedling Care**
Maintain 20–25°C after sowing. Within 7–10 days, spray 15–20°C warm water. Keep daytime temperature at 20–24°C and nighttime at 15°C. Increase ventilation as temperatures rise. Remove covers when temperatures stabilize above 10°C. Thin seedlings when they have 2–3 leaves, and transplant them at 20–25 cm spacing, aiming for 150,000–210,000 plants per hectare.
When seedlings reach 10 cm, transfer them to the greenhouse. Dig 5 cm trenches, irrigate, and spray 3g/kg urea every evening for 10 days. From mid-June to mid-August, focus on growth, applying nitrogen-based fertilizers with some phosphorus and potassium. After August, reduce nitrogen and apply 3g/kg potassium dihydrogen phosphate every 10 days for 3–4 times to promote lignification and full bud development.
2. **Greenhouse Construction and Transplanting**
2.1 **Greenhouse Structure**
Build a single-story vertical plastic film greenhouse, 8 meters wide and 40 meters long. Use soil walls, with a 2-meter-high back wall, 60 cm thick. Support with cement pillars and bamboo beams. Cover with polyethylene film and rice straw at night. Protect the back slope with corn stalks and straw.
2.2 **Transplanting**
Transplant seedlings between early November and late November. Before planting, mix 100 kg of diammonium phosphate with 5,000–10,000 kg of chicken manure, deep till 60 cm, level the bed, and plant 8–10 plants per square meter. After 10–15 days, manage temperature at 10°C during the day and 18–23°C during growth periods, with 13–15°C at night.
2.3 **Post-Planting Management**
Water immediately after planting. Second watering after harvesting two shoots. Mix 25 kg of diammonium and urea with water, and spray 0.5% urea and potassium dihydrogen phosphate alternately every other week. Roll up the front slope each morning to regulate temperature. Clear snow promptly to avoid damage. After 50 days, top buds reach 20 cm; harvest only the tips to encourage new growth. Retain 1–2 leaves at the base for regeneration. Avoid packing buds in plastic bags to prevent leaf loss. At the end of April, transplant seedlings back to the field. During June–July, spray paclobutrazol 300 times for dwarfing, then return to the greenhouse for continued growth and harvesting.
3. **Post-Planting Management**
3.1 **Shed Adjustment**
After leaf fall, there is a period of dormancy. If planted too early, keep the shed closed. If planted after late November, close the shed immediately. Raise temperature to stimulate germination.
3.2 **Temperature and Humidity Control**
After moving seedlings into the greenhouse, maintain 15°C for several days. After 8–10 days of heating, control daytime temperature at 18–24°C and nighttime at 12–14°C, keeping ground temperature above 15°C. Maintain 85% humidity. If low, mist branches during sunny mid-days. If high, ventilate during mid-day.
3.3 **Hormone Application**
Apply raw extract from twigs to the upper 4–5 dormant buds. Use 1 g granules per 100–120 shoots. Buds will sprout within 7–9 days, increasing yield by 10–20%.
3.4 **Harvesting**
Harvest flat buds when they reach 15–20 cm and color well. Early harvest affects yield; late harvest reduces quality. Pick terminal buds, leaving 1–2 leaves at the base. Harvest in the morning and evening, every 7–10 days, 4–5 times total. Spray foliar fertilizer 2–3 days before harvest, and apply ammonium nitrate 300 kg/hm² after picking. By mid-April, cut seedlings 10–15 cm above ground. Transplant to open fields with 30–40 cm spacing, 90,000 plants per hectare. Cultivate and train strong buds for next year’s seedlings.
3.5 **Pest and Disease Control**
No need for pesticides during budding. Seedlings may suffer from blight, damping-off, and root rot. Spray 25% carbendazim WP 600 times or 1% double effect Ling 500–700 times, every 7 days for 2–3 times. For pests like tortoiseshell caterpillars and moths, use 90% trichlorfon crystal 800 times or 40% dimethoate EC 150 times. If tea plant damage occurs, spray 15% daphthol cream 1500–2000 times for prevention.
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