Detailed Guide to Blueberry Cutting Propagation, Step-by-Step Instructions
There are many propagation methods for blueberries, such as cuttings, seed propagation, and division. At present, blueberries cultivated in China are usually propagated mainly by cuttings in production. Other methods such as seed seedling raising, rhizome cuttings, and division are also used. The propagation method varies by species. Highbush blueberry mainly uses hardwood cuttings, rabbiteye blueberry uses softwood cuttings, and lowbush blueberry can use either softwood or hardwood cuttings. Hardwood cuttings are mainly used for highbush blueberry, but rooting difficulty varies by cultivar. For example, 'Blue Line', 'Rubel', and 'Jersey' root easily from hardwood cuttings, while 'Bluecrop' is difficult to root.
Seedbed Preparation for Blueberries
1. Substrate selection: River sand, sawdust, peat, decomposed moss, etc. can all be used as cutting substrates, but when river sand and sawdust are used as cutting substrates, the rooted cuttings need to be transplanted, which is labor-intensive and affects seedling development. The ideal cutting substrate is decomposed moss, or a mixed substrate of peat and river sand (1:1).
2. Seedbed selection: Cuttings can be taken directly in the field, with the cutting substrate spread into a bed 1 m wide and 25 cm thick, and the length determined as needed. However, because air and ground temperatures are low with this method, the rooting rate is relatively low. The most widely used and relatively inexpensive option is a wooden raised bed: make a wooden box about 2 m long, 1 m wide, and 40 cm high, with a hard board nailed to the bottom with 0.3-0.5 cm mesh openings. The wooden box is raised off the ground with logs. This method can effectively increase substrate temperature and improve the rooting rate.
Blueberry Cutting Methods
1. Cutting selection: Cuttings should be cut from robust, pest- and disease-free trees. It is best to choose branches that are firm, well-matured, and healthy. Try to avoid selecting excessively vigorous shoots, branches with large pith, and branches damaged by freezing in winter. If viral disease occurs in the orchard, the tree from which cuttings are taken should be at least 15 cm away from diseased trees. Cutting wood is best taken from 1-year-old vegetative shoots. If there are not enough cuttings, 1-year-old flower bud shoots may be selected, and the flower buds should be removed when taking cuttings; however, flower bud shoots often have a lower rooting rate and poorer root quality. The position of the cutting on the branch also significantly affects the rooting rate. Using the base of the branch as cuttings, whether vegetative shoots or flower bud shoots, gives a markedly higher rooting rate than using the upper part of the branch as cuttings. Therefore, the middle and lower parts of branches should be selected for cuttings whenever possible.
2. Cutting time: When only a small number of seedlings is needed, cuttings are taken before spring budbreak (generally March to April), and inserted immediately after cutting, which avoids the need to store the cuttings. However, when raising seedlings in large quantities, cuttings need to be taken in advance. Generally, branch budbreak requires 800-1000 hours of cold, so the cutting time should ensure that the branches have accumulated sufficient chilling. Generally speaking, February is more suitable.
3. Preparing the cuttings: The cutting tool should be sharp and the cut surface smooth. The length of the cuttings is generally 8-10 cm. The upper cut is flat, and the lower cut is slanted. The lower cut should be located just below a bud, which can increase the rooting rate. After cutting, tie the cuttings into bundles of 50-100 and temporarily bury them in wet river sand or similar material.
4. Cutting method: Once everything is ready, water the substrate thoroughly to ensure moisture but without waterlogging, then insert the cuttings vertically into the substrate, leaving only one terminal bud exposed, at a spacing of 5×5 cm. Do not insert the cuttings too densely. Excessive density first causes poor seedling development after rooting, and second makes bacterial infection more likely, causing the cuttings or seedlings to rot. For highbush blueberry hardwood cuttings, rooting hormone treatment is generally not needed; many rooting hormones have little or no effect on rooting of hardwood cuttings.
Post-Cutting Management for Blueberries
1. Water management: After cutting, water frequently to maintain soil moisture, but avoid both overwatering and underwatering. If the water has been left in the sun for a long time and its temperature is high, let it cool before watering to avoid injuring the seedlings. The most critical period for water management is from early May to late June, when the leaves have expanded but the cuttings have not yet rooted; insufficient water can easily cause the cuttings to die. When the terminal leaves begin to turn green, it indicates that the cuttings have begun to root.
2. Fertilizer management: Do not apply any fertilizer to the substrate before cutting, and do not fertilize after cutting before rooting. After the cuttings root, begin applying fertilizer to promote seedling growth. Fertilizer should be applied in liquid form, using a complete fertilizer such as 13-26-13 or 15-30-4, at a concentration of about 3%, once a week. After each fertilization, spray water to rinse the fertilizer off the leaf surface to avoid damaging the leaves.
3. Transplanting method: Rooted seedlings generally overwinter in the seedbed, or they can be transplanted for tending in September. If rooted seedlings overwinter in the seedbed, soil should be banked up along both sides of the seedbed before winter.
4. Pest and disease management: During the rooting and seedling period, diseases are mainly controlled by ventilation and removing diseased plants. For seedling raising in a greenhouse or conservatory, ventilate promptly to reduce fungal diseases and lower the temperature.