How to Propagate Blueberries by Cuttings? A Detailed Guide to the Latest Methods
There are many propagation methods for blueberries, such as cuttings, seedling growing, and division. At present, blueberries cultivated in China are usually propagated mainly by cuttings in production, while other methods such as seed seedling raising, rhizome cuttings, and division are also used. The propagation method varies by species. Highbush blueberries are mainly propagated by hardwood cuttings, rabbiteye blueberries by softwood cuttings, and lowbush blueberries by either softwood or hardwood cuttings. Hardwood cuttings are mainly used for highbush blueberries, but rooting ease varies by cultivar. For example, Blue Line, Rubel, and Jersey root easily from hardwood cuttings, while Bluecrop roots with difficulty.
Seedbed Preparation for Blueberries
1. Substrate selection: River sand, sawdust, peat, and rotten moss can all be used as cutting substrates, but when river sand and sawdust are used as cutting substrates, the plants need to be transplanted after rooting, which is labor-intensive and affects seedling development. The ideal cutting substrate is rotten 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, with 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 frame bed, made from wooden boards into a wooden box about 2 m long, 1 m wide, and 40 cm high, with a hard board with 0.3-0.5 cm mesh nailed to the bottom of the box. The wooden box is raised off the ground on round logs. This method can effectively increase substrate temperature and improve the rooting rate.
Cutting Methods for Blueberries
1. Cutting selection: Cuttings should be cut from trees that are vigorous and free of pests and diseases. It is best to choose branches that are firm, well matured, and healthy, and to avoid choosing water sprouts, branches with large pith, and branches damaged by freezing in winter. If viral diseases occur in the orchard, cuttings should be taken from trees at least 15 cm away from diseased trees. The best cuttings are 1-year-old vegetative branches. If there are not enough cuttings, 1-year-old flower bud branches can be selected, and the flower buds should be removed when taking cuttings. However, flower bud branches often have a lower rooting rate and poor root quality. The position of the cutting on the branch also has a very significant effect on the rooting rate. Whether vegetative branches or flower bud branches, cuttings taken from the base of the branch have a noticeably higher rooting rate than those taken from the upper part of the branch. Therefore, the middle and lower parts of the branch should be selected for cuttings as much as possible.
2. Cutting time: When the number of plants to be propagated is small, cuttings are taken before spring bud break (generally March to April) and inserted immediately after cutting, which saves the need to store the cuttings. However, when propagating on a large scale, cuttings need to be taken in advance. Generally, branch buds require 800-1000 hours of chilling, so the cutting time should ensure that the branches have accumulated enough chilling. Generally, February is more suitable.
3. Preparing the cuttings: The cutting tool must be sharp, and the cut must be smooth. The length of the cuttings is generally 8-10 cm. The upper cut is flat, and the lower cut is slanted, with the lower cut located right below a bud, which can improve the rooting rate. After cutting, tie the cuttings into bundles of 50-100 each and temporarily bury them in wet river sand or similar.
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. Too dense planting first causes poor seedling development after rooting, and second makes them prone to bacterial infection, causing the cuttings or seedlings to rot. When taking hardwood cuttings of highbush blueberries, 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 overwatering or underwatering. If the water has been left in the sun for a long time and is warm, let it cool before watering to avoid damaging the seedlings. The most critical period for water management is from early May to late June, when the leaves have unfolded but the cuttings have not yet rooted, and insufficient water can easily cause the cuttings to die. When the top 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. Once the cuttings have rooted, begin applying fertilizer to promote seedling growth. Fertilizer should be applied in liquid form, using a 13-26-13 or 15-30-4 complete fertilizer at a concentration of about 3%, once a week. After each fertilization, spray water to wash the fertilizer off the leaf surfaces 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 on both sides of the seedbed before winter.
4. Pest and disease management: During the rooting and seedling period, disease control mainly relies on ventilation and removing diseased plants. When raising seedlings in a greenhouse or shed, ventilate promptly to reduce fungal diseases and lower the temperature.