Key cultivation and management techniques for 5°C tulip bulbs

5°C tulip bulbs need sufficient time to complete

development at each stage, and the treatment time required differs among varieties, so each variety has an earliest and a latest planting time. Within this period, growers can choose the most suitable planting time based on actual conditions and their own market expectations.

Preparation before planting

After the bulbs arrive, they should be planted immediately. If the soil temperature is above 16°C, they can be stored for at most 1-2 weeks. Store the bulbs in a cold room at 2°C-5°C, with 70% relative humidity and a certain amount of air circulation (0.5 m3 of air flow per hour per 0.1 m3 of bulbs). If ventilation is poor, even slight moisture can cause the spread of Penicillium.

For the planting site, use standard tulip plastic crates or lily plastic crates for cultivation whenever possible. If crate cultivation conditions are not available, tulips must be grown on raised beds to reduce the possibility of soil pathogens infecting the tulip root system.

Growing medium: to facilitate rooting of tulips and ensure the plants have a good root system, the pH of the growing medium should be 6-7, the EC value must be below 1.5 mS/cm, and it should be loose, sterile and well drained. Adding peat can lower excessively high soil pH and increase soil looseness. Soil with high EC must be irrigated 2 months in advance to leach salts.

Prepare the planting site in advance. 7 days before planting, thoroughly water the medium to be used for planting tulips. After watering, cover the entire greenhouse with 2 layers of shade netting (south) or straw curtains (north), while keeping the greenhouse ventilated to lower the temperature inside the greenhouse.

Cultivation management

Bulb disinfection: if the soil temperature is above 14°C when planting tulips, it is recommended to disinfect the bulbs. Before disinfection, first peel off the brown skin around the bulb base plate. The specific disinfection method is to soak the bulbs in a solution of 0.2% carbendazim + 0.1% etridiazole for 15 minutes.

Planting method: after removing the outer skin of the bulb base plate, plant the bulbs in soil with 30-40 cm of loose soil in the surface layer. When planting, make sure the bulbs are covered with 1-2 cm of soil. Generally, 200 bulbs can be planted per sq m. Water once after planting is completed.

Rooting stage care: about 3 weeks after planting tulips is the rooting stage. During the rooting stage, keep the soil temperature at the bulb base plate at 9°C-12°C. Soil temperature can be lowered by heavy shading and watering with cold water, and drastic temperature changes should be avoided as much as possible. During the rooting stage, tulips do not need light. The greenhouse can be covered with 2 layers of shade netting or straw curtains while ensuring greenhouse ventilation. During the rooting stage, do not water again unless the medium is very dry, in which case apply a small amount of localized supplemental water.

Heating: after the rooting stage, the plants begin to receive light, and shade materials such as shade netting need to be removed, while ensuring the greenhouse temperature remains at 15°C-17°C continuously until flowering. At this time, many places enter deep winter. To reach this temperature, heating is needed, especially at night. Never use the method of closing the greenhouse to keep warm, because this makes humidity inside the greenhouse too high and can very easily lead to a series of physiological diseases and gray mold. When heating, avoid letting exhaust gas and smoke enter the greenhouse, otherwise it may cause all tulips in the entire greenhouse to die.

Water management: after planting the bulbs, water appropriately to provide sufficient water for plant growth. After watering, pay attention to ventilation, and do not let the plants stay wet overnight, so as to avoid infection by gray mold.

Control relative humidity between 60%-80%, and check it frequently. It is best to place a hygrometer at the top position of the plants. If relative humidity is too low, plant development will be delayed; if too high, it will increase the probability of lodging, gray mold, plant bending and blind flowers. Excessively high relative humidity can be reduced by ventilation, and if conditions permit, it can be done simultaneously with slight heating.

Fertilization: tulips usually do not need fertilization. If necessary, consider applying some nitrogen fertilizer. After the bulbs have rooted, apply 2 kg of calcium nitrate per 100 m2, divided into 3 applications, with each fertilization interval of one week. The calcium ions in calcium nitrate can also prevent tulip damping-off.

When tulips grow to 5-10 cm tall in the greenhouse, check their growth frequently and deal with bulbs infected by gray mold and Fusarium as early as possible. Dig out all bulbs that have not sprouted or are growing very slowly, because these bulbs may be infected by gray mold and Fusarium. The ethylene gas released by bulbs infected with Fusarium can damage surrounding healthy plants.

The following problems may occur during cultivation:

(1) During the rooting stage, even if 2 layers of shade netting are used to cover the entire greenhouse, the air and medium temperature in the greenhouse may still be too high, even exceeding 20°C (especially in the south), resulting in poor rooting, severe blind flowers later, or stunted plants.

(2) After the rooting stage, many greenhouses have no heating conditions, and the air temperature in the greenhouse will be below 15°C, even below 10°C at night. Being in such an environment for a long time can cause the plants to fail to flower on time, delaying the flowering period.

(3) Even when all the above cultivation conditions are met, only about 85% of the finished product rate can be guaranteed. It is very normal for the remaining bulbs to develop various problems. According to international standards, under conditions that satisfy tulip growth, the flowering rate of tulip bulbs should be 85%.

Harvesting and storage of cut flowers

Harvest can be done once the flower buds show color. At this time, the buds have not yet opened, which is beneficial for storage and transport. Usually, the whole plant is harvested with the bulb. After the cut flowers are harvested, immediately tie them into bunches and place them upright in clean water at 2°C-5°C for 30-60 minutes. Before shipping, place the packaged cut flowers upright in the storage room to prevent the flower stems from growing bent; maintain appropriate humidity to prevent the plants from drying out; use certain ventilation measures to keep the plants dry and avoid gray mold infection. Do not store for more than 1-2 days. With long storage time, cut flowers are more likely to be damaged by ethylene and gray mold due to drying and lack of nutrients. If long-term storage is necessary, store them with the bulbs.