Tulip Blindness Prevention and Cut Flower Production Techniques
Tulip (Tulipa gesneriana L.), also known as foreign lotus and grass musk, is a perennial bulbous ornamental flower of the genus Tulipa in the Liliaceae family. It is one of the most famous flower varieties in the world today and has long been known as the "king of flowers" [1,2,3]. China still lags behind in box-type cut flower production technology, the causes of blindness formation, and prevention techniques for tulips, which has restricted the development of tulip cut flower production. The flower base of the Hebei Academy of Forestry Sciences, while vigorously developing soilless cultivation of tulips, has conducted preliminary research on the biological characteristics of tulips, root forcing treatment in soilless cultivation methods, growth period management, and pest and disease control [4]. Based on a review of relevant literature and combined with production practice, this paper focuses on box-type cut flower production technology for tulips, the causes of blindness, and its prevention, aiming to provide an effective scientific basis for advancing the standardization, internationalization, and commercialization of tulip cut flower production in China.
Tulip Cut Flower Production Techniques
Tulip Box Cultivation
Tulip cut flower production uses plastic boxes or wooden boxes measuring 60 cm x 40 cm x 20 cm, with gaps required around the sides of the box. The substrate should preferably be coarse sand and vermiculite with excellent permeability and water retention. Before planting, the substrate must be sun-exposed for disinfection. A three-layer cultivation method is used for planting [5], that is, the upper and lower layers of the box are coarse sand with thicknesses of 3 cm and 6 cm respectively, and the middle layer is vermiculite with a thickness of about 8 cm. For tulip box-type cut flower production, 9 degrees C bulbs should be used, and the flowering period should be controlled. When planting, 4/5 of the bulb should be placed in the vermiculite, and the planting density should preferably be 400 bulbs per sq m, that is, about 100 bulbs per box. Tulips exhibit phototropism during the growth period, so the direction of the box should be adjusted in a timely manner. After thorough watering, root forcing treatment should be carried out under dark conditions, with the temperature controlled at 9-11 degrees C and the substrate moisture maintained at 90%-100%. The rooting time requires 4-6 weeks. After root forcing is completed, the bulbs are moved into the greenhouse and require 25-35 d (varying by variety) to bloom. The time for moving them into the greenhouse should be determined according to flower demand. During the growth period, the temperature should be controlled at 15-20 degrees C and the relative air humidity (RH) should be controlled at 60%-70%. This can alleviate the RH in the greenhouse, help keep the plants in a dry state, effectively inhibit pathogen infection, and reduce the occurrence of diseases. Under forcing cultivation conditions, tulip growth and flowering mainly rely on nutrients stored in the bulb itself, and generally no additional fertilization is needed.
Harvest Time
The optimal harvest period for tulips is when the flower develops to a semi-transparent state, that is, when the flower color has fully formed. Harvesting is generally carried out at around 7-8 AM or around 5 PM. During the flowering period, harvest should be done after the flowers close in the evening.
Harvesting with Bulbs
At harvest, the bulbs are pulled out together with the plants, that is, harvested with bulbs, while retaining 2-3 leaves at the base. Harvesting with bulbs can reduce the spread of soil-borne diseases; extend the storage time of the flower stems; and if the height is insufficient, the 2-3 cm of the stem can be used to make up the height. The cut flower height of tulips is generally 45-70 cm.
Post-harvest Handling
After harvest, place the flowers first in a cold storage at 2-3 degrees C and RH 90% for 2 h. Then remove the bulbs, tie the flower heads in the same direction, generally 10 stems per bunch, 5 bunches per package wrapped in newspaper, place them in water at 1-2 degrees C, and allow them to absorb water for about 24 h. When storing in cold storage, place them upright and protect from light to prevent the stems from bending. Storage time should not exceed 3 d, otherwise the flower quality will be affected.
Causes and Prevention of Blindness
Blindness is a physiological phenomenon in which the flower stalk cannot emerge or shrivels after emergence and cannot bloom normally due to poor bulb quality or unsuitable environmental conditions during the growth period. It is the greatest obstacle in tulip production.
Formation of Blindness
The main causes of blindness formation are as follows:
(1) Bulb quality problems. One case is that cold treatment begins before flower bud differentiation is fully completed and when stored nutrients are insufficient; another is poor bulb quality caused by insufficient cold treatment time or inappropriate temperature control (the optimal temperature is 17-20 degrees C), resulting in poor flower bud development and causing blindness during the growth period.
(2) Poor root system. This mainly occurs during root forcing treatment when the temperature is too high or too low, water is lacking, or the root forcing time is insufficient, resulting in short roots and weak water absorption capacity, which later causes blindness.
(3) Unsuitable environment. During the growth period, high temperature and high humidity causing excessive vegetative growth, or two consecutive droughts, can both easily lead to blindness.
Prevention of Blindness
The prevention of tulip blindness should focus on ensuring bulb quality, performing root forcing treatment well, strengthening management during the growth period, and comprehensively preventing the occurrence of blindness. In production, the following work should be done according to the causes of blindness:
(1) Select high-quality bulbs. Before planting, conduct strict sampling inspections of bulbs to check whether flower bud differentiation is complete and whether development is normal, so as to determine the quality of the bulbs and the blindness rate.
(2) During root forcing, strictly control the temperature at 9-11 degrees C, always maintain substrate moisture above 95%, and strictly carry out root forcing treatment under dark conditions to promote robust root growth. When the roots reach about 10 cm, begin moving them into a heated greenhouse to start above-ground growth. Because tulip roots are relatively brittle and have no regenerative capacity, damage to the root system should be avoided in production to prevent blindness.
(3) During the growth period, control the greenhouse temperature at 15-20 degrees C. When it exceeds 25 degrees C, ventilate and cool in a timely manner. Water once every 3-4 d on average, and control the substrate water content above 90% to avoid drought.
Summary
Tulip box cultivation has the advantages of effectively utilizing space and saving large amounts of land; greatly increasing flower yield per unit area; good mobility, which can effectively solve the problem of plant phototropism; and avoiding cross-infection of pathogens.
The procedure for harvesting tulip cut flowers: harvest with bulbs -> store in cold storage (2-3 degrees C) -> remove bulbs, bundle and package -> store tulips to be sold in cold storage (below 5 degrees C) -> sell.
In addition to bulb quality problems, the occurrence of tulip blindness is mainly caused by poor root development and water deficiency caused by unsuitable environmental conditions. The focus of prevention should be ensuring bulb quality, performing root forcing treatment well, strengthening temperature management during the growth period, and maintaining sufficient moisture. This can effectively reduce the occurrence of blindness.
Box-cultivated tulips can also be used for potted cultivation, that is, when the flowers show slight color, transplant them into pots while minimizing root damage. After planting, place them in a shady area with the temperature controlled at about 10 degrees C, and after 2-3 d, they can be sold.