Cultivation requirements for tulip bulbs after 5°C low-temperature treatment

1. Carefully remove the brown outer skin wrapped around the roots before planting.

2. Plant the bulbs in slightly moist soil at the specified number of bulbs per sq m and the correct depth.

3. Provide the recommended temperature conditions at bulb depth and at plant height in the greenhouse.

4. The relative humidity in the greenhouse must never exceed 80%.

5. Keep the soil in the greenhouse at the optimal moisture content.

6. Regularly check the plants, temperature and relative humidity; always use annually calibrated testing equipment.

Bulb peeling

Bulb peeling means carefully removing the brown layer covering the roots. The advantages of peeling 5°C bulbs before planting are:

-- Preventing root damage caused by contact between the roots and residues of pre-planting bulb disinfection.

-- Allowing shallower planting, avoiding attack on the stem by Rhizoctonia fungi.

-- Promoting uniform root growth, resulting in stable growth and flowering of the whole plant.

-- Shortening the greenhouse cultivation time by 3-4 days.

-- Diseased bulbs are easy to identify and remove.

The disadvantages are:

-- Increased risk of bulb damage, especially severe damage to the roots.

-- Requires extra labour.

Planting requirements

The number of plants planted depends on the variety, bulb size and harvest time.

For peeled bulbs, plant with the nose of the bulb exposed above the soil. The soil structure should be in very good condition at this time, and water immediately after planting to prevent drying out and dehydration.

For unpeeled bulbs, the planting depth is 2-4 cm, covering the top of the bulb, which promotes the rooting process.

During bulb planting, the subsoil should be very loose; do not push the bulbs roughly into the soil. Correct planting should ensure reduced damage to the root primordia, where roots may sometimes already be present. After planting, place a layer of coarse peat on top of the growing medium to prevent damage to the soil structure during watering.

Greenhouse temperature

After planting, the soil temperature at bulb depth is important. To prevent soft rot, keep the soil temperature as low as possible for two weeks after planting, preferably 10°C or lower. During the earliest planting period in October-November, this temperature is difficult to maintain and may be higher. If the soil temperature in the greenhouse rises above 17°C, it is best to delay planting by 1-2 weeks. This is why not only should a sufficiently cool planting site be chosen, but correct measures should also be taken before and after planting to ensure the soil temperature is as cool as possible. This can be achieved through the following measures:

-- Apply mulch to the soil surface before planting, and cover the soil with straw etc. after planting to prevent sunlight exposure.

-- Do not cover the greenhouse in the two weeks after planting; instead, shade cloth may be used during the early stage before planting.

-- If mulch or shading is used, provide sufficiently large ventilation.

-- Before and after planting, spray the greenhouse soil with cold water.

Relative humidity

If the relative humidity in the greenhouse is too high, it will inhibit the transpiration process of the bulbs, leading to growth disorders such as damping-off of leaves, stems and flowers, water-soaked stems, and even flower wilting. In addition, high relative humidity in the greenhouse will also increase infection by Botrytis fungi, producing weaker and thinner plants.

To prevent such problems, the relative humidity should be kept below 80%. Ventilation can achieve this. If there is little wind and the weather is stuffy, a slight increase in temperature together with ventilation is recommended.

When cultivating varieties with many leaves that are relatively sensitive to damping-off (such as Leen v.d. Mark), installing fans to blow air horizontally in the greenhouse can effectively promote evaporation. Such varieties should be planted at a lower density.

Watering

Water before planting to lower the soil temperature. Bulbs should be planted in slightly moist soil; watering after planting is beneficial for early rooting. After planting, a certain amount of water is needed; watering from above through a sprinkler system is beneficial for rooting. Generally, water supply should be premised on maintaining the integrity of the soil structure.

During cultivation, water appropriately; overwatering is very dangerous. The closer to harvest time, the more a low-volume water supply system should be used.

It is difficult to specify the number of waterings; it depends on many factors, including:

-- The growth stage of the plant; the more leaves, the more transpiration.

-- Climate.

-- The amount of ventilation.

-- The variety used.

-- Soil type.

-- Total salt content.

The standard used in practice is that the soil under the bulb can be squeezed into a ball, which means there is sufficient moisture for plant growth.

Water when the plants are short of water, generally in the morning. Ventilation after watering can reduce the relative humidity between the plants. If harvesting has already begun, watering is usually also done after harvest.

Cultivation cycle

The greenhouse cycle of a variety depends on the temperature during storage and the temperature in the greenhouse; the humidity level in the greenhouse also affects the cultivation cycle.

Greenhouse control

First, the temperature and relative humidity of the air at plant height in the greenhouse must be controlled throughout the entire cultivation cycle. Use annually calibrated thermometers and hygrometers for measurement.

When tulip plants reach a height of 5-10 cm, inspect the plants for grey mould, rot and diseases caused by Botrytis fungi. Plants with no stem development or very slow stem development may be infected by Fusarium; remove them immediately upon discovery to prevent the harmful effects of ethylene gas produced by these diseased plants on surrounding plants.

Plants infected by Fusarium can spread large numbers of spores before symptoms appear; as long as these spores are above the ground, they may cause infection in other plants. Therefore, timely and careful removal of these bulbs is crucial.

Fertilisation

Usually, fertilisation is not necessary, but if the bulbs cannot absorb enough nitrogen, some nitrogen fertiliser may be considered. After the bulbs have rooted well, apply 2 kg of calcium nitrate per 100 sq m, broadcast in three applications with an interval of one week between each.