Detailed Explanation of Hardwood Cutting Propagation and Cultivation Techniques for Azaleas
Azaleas have graceful plant shapes, abundant and colorful flowers, and high ornamental value, with broad market application prospects, and are therefore widely used in landscape engineering. Let's learn together how azaleas are propagated and cultivated through hardwood cuttings.
Cutting is the main propagation method for deciduous, semi-evergreen and evergreen azaleas, and is widely applied. However, azalea cuttings are difficult to root, and grow slowly after cutting and transplanting. Therefore, in response to problems such as the large demand for azalea seedlings, difficult rooting of cuttings and slow growth, in recent years scholars at home and abroad have carried out cutting propagation trials on some species and found that: cutting rooting is affected by endogenous factors such as endogenous hormones in the cuttings, rooting cofactors, nutrient levels and antioxidant enzyme activity, while exogenous auxins can regulate the physiological activities of cuttings, induce changes in enzyme activity and cofactors, thereby promoting cell elongation, division, root primordium differentiation and adventitious root formation; cutting time is closely related to the degree of lignification and physiological characteristics of the cuttings, and is another key factor affecting plant cutting rooting.
1. Seedbed Construction
The seedbed is set up inside a glass greenhouse or plastic tunnel, with red bricks or cement bricks used for the bed edges. A drainage hole is reserved every 100cm at the bottom of the seedbed, then stones, pebbles and coarse sand are added successively from bottom to top to increase drainage and aeration of the seedbed; on top of the coarse sand, a 10-15cm thick cultivation substrate is laid, raked level and lightly pressed to make the seedbed flat, then watered thoroughly; to control the temperature, humidity and light of the seedbed environment, an arched plastic tunnel is built over the seedbed, equipped with automatic misting facilities inside, and a shade net is set up 30cm above the plastic tunnel; after the seedbed is completed, the substrate and surrounding environment are disinfected with a 500-fold carbendazim aqueous solution.
2. Collection and Preparation of Cuttings
Select vigorous adult East Azalea (Rhododendron) plants about 5-25 years old as mother plants for cutting collection. In June, collect healthy lignified branches (also called hardwood) from the previous year on the plant canopy, spray water to keep them moist and transport them back indoors promptly; select strong, upright small branches free of pests, diseases and flower buds (with bud scales), cut them into 10-25cm long cuttings, with hardwood length 8-10cm, retain 2-5 branches at the branching point, and remove the tender shoots 2-3cm from the top of the branches; remove the leaves at the base of the cutting, retain 3-4 leaves on the upper part, then cut off 1/2-2/3 of the leaves according to leaf size to reduce water evaporation; on one side of the base of the cutting, use a grafting knife to remove a 1.0-1.2cm long strip of cortex and cambium, with the cut surface at more than 45° to the branch, to facilitate absorption of rooting agent and formation of a large area of callus tissue.
3. Callus Treatment
Treat the cuttings with 1000mg/L IBA aqueous solution for 1min, then soak the base of the cuttings in 500mg/L NAA aqueous solution for 1min, and air-dry naturally for 12 hours; place the cuttings in an environment at 23-26°C and 60-70% relative humidity for 6 hours; then place the cuttings in an environment at 10-15°C and 40-60% relative humidity for 2 hours; finally dip the base of the cuttings in ABT rooting agent solution (ABT rooting agent:water = 1 gram:2kg) for 3-5 seconds, and place them in an environment at 23-26°C and 50-60% relative humidity for 24 hours.
4. Cutting and Management
The cuttings should be inserted immediately after treatment. Before insertion, first use a small bamboo stick to make a small hole to reduce mechanical damage to the cutting tissue from the substrate; the plant and row spacing between cuttings is 15×15cm, the insertion depth is 1/3-1/2 of the cutting length, and after insertion, spray water thoroughly. During the trial period, an automatic intermittent misting system is used to replenish water and increase humidity: 5min/4h during the day, 2min/4h at night, and after 40 days the misting frequency is gradually reduced; the temperature and light intensity inside the tunnel are adjusted according to weather conditions through ventilation on both sides of the plastic tunnel and the shade net respectively (air temperature inside the tunnel controlled at 20.0-30.0°C, relative humidity 80.0-95.0%); when the temperature is higher than 30.0°C, open the plastic tunnel for ventilation to lower the temperature; to reduce contamination, promptly remove fallen leaves and rotten cuttings from the seedbed, and alternately spray once every 7-10d with 500-fold carbendazim or 1000-fold thiophanate-methyl aqueous solution.
After 50 days, observe the rooting of the azaleas, checking once every 10 days. When more than 3 roots have formed at the bottom and the root length is more than 2cm, transplanting can begin. The planting substrate for transplanting is peat soil:yellow soil:perlite:vermiculite at 4:1:1:1. Water thoroughly after transplanting to settle the roots, set up a shade net at 50cm above ground with a shading rate of 50%, cover with the shade net from 9 am to 5 pm and remove it at other times; 2 months after transplanting and establishment, remove the shade net.
Using this propagation and cultivation method to propagate East Azaleas by cuttings, the callus formation rate reaches as high as 95%, the rooting rate reaches 90%, each plant forms more than 3 roots, and root length exceeds 2cm. In the second year, the growth height reaches 30-50cm, with strong branches, and they can leave the nursery. The technique lies in selecting lignified branches from the previous year as cuttings, whose front end carries a transitional branch from current-year semi-lignified to lignified, and the cutting is more than twice the length of traditional cuttings; after rooting, it becomes a plant with multiple branches, and after rooting and transplanting in the same year, it can leave the nursery as a strong seedling in the second year, solving the previous situation where branching only occurred in the second year after cutting survival and strong seedlings could only leave the nursery after the 3rd year; moreover, the seedlings of this technique have strong branches and the whole plant grows rapidly.
That is all for today's content. In terms of cutting time, this technique breaks traditional ideas by cutting in June-July, which facilitates rapid rooting and rapid development of seedlings after rooting. It solves the difficulties of azaleas being difficult to root from cuttings, low propagation rate and slow production, and effectively improves the rooting rate and rooting quality. This technique requires no special treatment, is simple and easy to operate, and is an effective method for large-scale rapid propagation of azaleas, especially suitable for industrialized seedling production of evergreen azaleas.
How to Propagate Azaleas by Cuttings
How to propagate azaleas by cuttings refers to the cutting method for azaleas. So, how do you propagate azaleas by cuttings? Now let us tell you how to propagate azaleas by cuttings!
How to propagate azaleas by cuttings?
Azaleas can be propagated by five methods: cuttings, grafting, layering, division and sowing, among which the cutting method is the most common and produces the largest number of propagules; layering produces seedlings fastest, grafting propagation is the most complex, and grafting is only used for varieties that are difficult to root from cuttings, while sowing is mainly used for breeding varieties.
For cutting propagation, a new shallow clay pot with a 20cm diameter is best, because it has good air permeability and is easy to root in. A culture soil mixed from 20% humus garden soil, 40% horse manure crumbs and 40% river sand can be used as the substrate. The best times for cutting are spring (May) and autumn (October), when the temperature is between 20-25°C, most suitable for cutting. When cutting, select current-year semi-lignified, well-developed and vigorous shoot tips as cuttings, use very sharp scissors; cut 6-10cm with nodes, the cut must be smooth and neat, remove the lower leaves and keep only 3-4 small leaves at the top. Buy 1 ampoule of vitamin B12 injection, open it, dip the cutting in the liquid, take it out and let it dry for a while before cutting. Before inserting, the culture soil in the pot should be sprayed moist with a watering can the day before, but not too much, so that by the next day it is just moist, most suitable for cutting. The insertion depth is 3-4cm. When inserting, first use chopsticks to poke a hole in the soil, then insert the cutting, press the soil firm with your hands so that the pot soil and cutting are in full contact, then water thoroughly once. After insertion, the flower pot is best covered with a plastic bag, with the bag opening tied with a string, opened when watering is needed, and tied again after watering. The pot that has been cut should be placed in a place without direct sunlight; the pot soil of the cutting should be sprayed with water every day for 10 days, once on cloudy days except rainy days, and twice when the climate is dry, but the amount of water sprayed each day should not be too much. After 10 days, still frequently pay attention to keeping the soil moist. Shade should be provided within 4-5 weeks, until after sprouting, when it can gradually receive some sunlight. Rooting generally takes about 2 months. After that, it is only necessary to shade for 2-3 hours at noon, and the rest of the time it can be exposed to light, so as to facilitate photosynthesis and manufacture nutrients on its own.
How to Care for Azaleas
How to care for azaleas——Soil:
Generally, the cultivation methods of plants and flowers cannot be separated from a good soil environment, and for azalea cultivation methods, the soil environment is even more important. There are many ways to mix the culture soil for cultivating azaleas; because cultivated varieties differ, but first of all the following conditions must be met: loose, well-drained, well-aerated, acidic soil, rich in humus, with sufficient base fertilizer.
How to care for azaleas——Watering:
As everyone knows, watering is a very important task, and for azalea cultivation methods, watering skills are very important. Because azalea roots are fine, when watering, care should be taken not to water too much and of course not too little, just appropriately. Moreover, watering is best done in the morning and evening, which helps azaleas absorb water well.
How to care for azaleas——Fertilizing:
Azaleas are a very undemanding flower; they do not need much fertilizer to grow, so when fertilizing, care should be taken not to apply too much. Excessive fertilizing will make it difficult for azaleas to absorb and cause death; appropriate fertilizing is what allows azaleas to grow well and produce beautiful flowers.
How to care for azaleas——Sunlight:
Among azalea cultivation methods, another very important and indispensable one is the absorption of sunlight. For plants and flowers, promoting photosynthesis is very necessary. Therefore, the growth of azaleas cannot be separated from sunlight, but they cannot be exposed to the sun all day either; suitable sunlight can make azaleas produce even more beautiful and charming flowers.
Azalea Propagation Methods and Key Points of Soilless Cultivation Techniques
Azaleas are a world-famous flower and one of China's top ten famous flowers. There are about 900 species of azaleas in the world, and China has more than 530 species. Because azaleas are short plants that bloom in all four seasons, with double flowers and extremely high ornamental value, they can often be seen in residential communities and plazas. Today, what the editor wants to discuss is azalea propagation methods and the key points of soilless cultivation techniques.
1 Morphological Characteristics
Azaleas are evergreen, semi-evergreen or deciduous shrubs or small trees, with plant height varying from 0.4-4m, and very short brown or brownish hairs often on the young branches. Flowers are terminal or axillary, funnel-shaped or bell-shaped, with bracts, corolla diameter 2-6cm, in many colors such as white, yellow, pink, orange, violet-red and rose-red, with 5-10 stamens. The fruit is a capsule, the ovary has 3-5 locules, and the seeds are tiny.
2 Ecological Habits
Azaleas prefer a loosely shaded environment, and avoid exposure to sunlight; their cold tolerance varies greatly depending on the place of origin. Azaleas are typical acid-soil plants and grow well in an environment with a hydrogen ion concentration of 31.63-316.3 μmol/L (pH 5.5-4.5). In gardens in northern China, there are still no open-field plantings of azaleas in mass; in alkaline environments, azaleas turn yellow due to lack of iron and manganese and then shed leaves and die. The mechanism by which alkalinity causes leaf chlorosis is still unclear.
3 Propagation Methods
Propagation methods include sowing, cutting, layering, grafting and division. Cutting and grafting can maintain the genetic traits of the variety and can form a commercial production process; sowing is conducive to hybrid breeding and selecting superior individual plants; cuttings use green branches, selecting semi-lignified branches, and the survival rate is high when carried out during the plum rain season. The cutting substrate is also one of the key factors affecting survival. Azalea cuttings require rich nutrients, good aeration and moisture conditions around the base of the cutting, which can be provided by mist culture and perlite culture. The grafting method can fully exploit the advantages of the rootstock root system and the fine characteristics of the scion, cultivating a single plant that combines the advantages of both. The scion is taken from the tender shoots of superior varieties, with the lower leaves removed and only 3-4 small leaves kept at the top, and the base cut into a wedge shape with a cut surface 0.5-1.0cm long. The rootstocks used include 'Guifei Zuijiu', 'Yu Hudie' and 'Zi Hudie'; generally the original species of Rhododendron mucronatum is not used.
4 Soilless Cultivation Management
4.1 Substrate
4.1.1 Provide an acidic environment: such as pine needles, peat and sawdust, all of which are acidic substrates.
4.1.2 The roots in the substrate should not be air-dried by dry weather: azalea roots are very likely to die from air-drying, so it is best to use a mixture of peat and vermiculite or perlite.
4.1.3 Retain soil and fertilizer and allow aeration: correctly handle the relationship between acidity, aeration, water retention and fertilizer retention. When planting, consider that with the pot bottom not leaking, first the acidity of the substrate should be at a hydrogen ion concentration of 3.16-31.63μmol/L (pH 5.5-4.5), while maintaining good aeration; nutrients and water can be ensured through watering and applying nutrient solution.
4.2 Requirements for Nutrient Solution Cultivation
4.2.1 pH: hydrogen ion concentration 3.16-31.63μmol/L (pH 5.5-4.5), maintaining the most suitable environmental acidity for azalea roots.
4.2.2 Complete nutrition: supply the various nutritional components needed according to the growth needs of West Azaleas, otherwise single-salt toxicity is easily caused.
4.2.3 Large acid-base buffering capacity: the hydrogen ion concentration of the nutrient solution does not decrease significantly due to the addition of alkaline substances
4.3 Watering
West Azaleas are not tolerant of alkalinity. Usually the groundwater used in cities has a hydrogen ion concentration lower than 100nmol/L (pH higher than 7). Watering with groundwater easily causes azalea leaves to turn yellow, shed and even die. Therefore, to avoid this situation, a water vat can be set up where azaleas are planted, and the water in the vat left in the sun for a few days; at the same time, vinegar essence or edible vinegar can also be used to adjust the hydrogen ion concentration of the water, about 1 spoon of edible vinegar mixed with 500mL of water.
4.4 Management
The main management methods for azaleas are: they like shade and avoid exposure to the sun, like coolness and avoid stuffiness, like acidity and avoid alkalinity, and like light fertilizer and avoid heavy fertilizer.