Q: Can I do notching for trees right after planting to increase the number of feathers?
Yes, if you get trees from nursery with a little number of branches (feathers), you can use notching to induce branching. This is mainly important for trees intended for high-density training systems (e.g. tall spindle) and to avoid or reduce the chances of blind wood. Younger trees are more responsive to notching than older trees. You can use a hacksaw or a small knife to cause a notch above the bud as shown in the image attached. In notching, we remove a very small piece of bark without hurting/damaging the wood. This promotes branching by disturbing the hormone (auxin) that prevents the formation of lateral shoots. You should mainly target the area between 30-60 inches above the soil surface for notching. Although you can start notching directly after planting, waiting until new shoots are between 1-3 inches long would be better as you can easily distinguish the buds that failed to break.
Q. Does applying PGRs to the notched area increase branching in the newly planted trees?
That’s right. You may consider adding a 6-BA compound (e.g. Promalin) to the notched area by using a high concentration (12 oz in 5 gallons of water) and a backpack sprayer. Other researchers even suggested mixing Promalin and Maxcel and spraying them together to induce branching and enhance the growth of the new shoots. To do so, you need to mix 5 tablespoons of Maxcel, 1.5 tablespoons of Promalin and 2.4 ml of Regulaid (a surfactant) in a 1-quart spray bottle and spray it as a mist to the notched area. This will enhance branching significantly.
Q. Is notching and PGR applications effective with older apple trees?
For 1 and 2-year old apple trees, notching alone can be effective but again, a mist spray of Promalin alone or Promalin and Maxcel as indicated above will enhance branching and help the tree fill the space much quicker. This time of the year (between the tight cluster and open cluster) is just perfect for both notching and PGR applications. You may still do that until full bloom and after bloom, but the risk of shoot blight increases after bloom and notched areas will serve as entry sites for the fire blight bacterium. This risk can also be partially with seasonal streptomycin sprays. The same rules apply for enhancing branching on the blind wood of older apple trees (> 3 years).
Q. Can I just use PGRs applications without notching to induce branching in non-bearing and bearing apple trees?
Yes, you can use 6-BA products alone but you have to follow the instructions on the label for the concentration and application timing for bearing and non-bearing apple trees. You can use Maxcel at 250-500 ppm (128 oz/40 gal/acre) to induce branching in non-bearing apple trees. Applications should be made when terminal shoots are 28-30 inches long. For bearing apple trees, you can use spray Promalin solution to the blind wood at a concentration of 0.25-1 pint in a 5 gal of water, applied at 1-3 inches of new terminal growth.
Q- I have a lot of blind wood in the top part of the tree; is there anything other than notching and PGRs I can do to fix that?
At the time of dormant pruning, I would suggest you remove 2-3 large limbs by making a bevel cut and follow this with notching and PGR sprays two weeks before bud break. Leaving many large limbs in the tree sucks up the carbohydrate resources from the main trunk and makes it hard for any new branches to develop in the leader, causing blind wood.
Dr. Sherif M. Sherif, Assistant Professor, Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center, 595 Laurel Grove Road, Winchester, VA 22602. Email: ssherif@vt.edu; Tel: 540-232-6035