[This is the second part of a 2-part article which will cover bud grafting, approach grafting new branches /roots, and layering techniques.]
Most of the information and is from the Pennsylvania State University Horticulture Correspondence Course #11 and #86, as well as from notes taken in a workshop presented by Katheryn Taylor from the Dept. of Agriculture, University of Georgia, presented at the Bainbridge public library on 2/10/05. Also, some of the diagrams are from Bonsai Today,issue #33, as well as from a few internet websites.
Branch Grafting (cont.)
2) Approach Grafting (new branches or roots):
Branches: During the active growing season, a groove is cut into the stock’s bark just large enough to hold the new branch tightly and just deep enough so that the new branch is flush with the trunk. The scion can be from an existing branch which is bent into place, or another plant in its own pot or planted into the stock tree’s pot. Secure the new branch with staples or push pins and seal the cut with putty-type sealant.
Roots: A variation of the approach graft . However, instead of grafting in order to produce a new branch, this technique is to generate a new surface root where one is needed for a more balanced nebari. Plant a rooted cutting at the base of the stock tree where a surface root is needed. After the graft has taken, cut off the upper portion of the graft, leaving the lower section which has become the new root. Carry out this technique very early in the Spring at repotting time. Some sources suggest waiting an extra year after the graft takes, before severing the upper portion of the graft. Other sources suggest cutting the upper portion back gradually over a couple of years before cutting it flush with the trunk.
Bud Grafting: Bud grafting is sometimes preferred over branch grafting because it is simpler, often more successful, and can be done over a longer period than other grafting methods, though it is usually performed during the active growing season. The important points are the same as branch grafting – that is, both cambiums must meet and the graft should be kept from drying out. The reason for bud grafting is to create a limb or new apex where one is needed. Some sources suggest positioning the graft to face Northeast, in order to avoid the strongest sun exposure until the graft takes. Other sources suggest not performing bud grafting if the temperature is above 90*. The bud should come either from the same tree or from one of the same species. Mature buds should be taken from the current season’s growth and not allowed to dry out before grafting. If a leaf is attached to the bud, remove it but leave part of the petiole as a handle for grasping during the grafting procedure. Finish the job by tying everything down using rubber strips, raffia, or waxed twine. If the bud remains plump and does not dry out and turn brown after a few weeks, it has probably grafted successfully. The bud will remain dormant, however unless the area above it is severed down to the cambium (for a side branch) or completely removed (for a new apex). During the next growing season after the bud graft has taken, cut a slit ¼ inch above the bud, down to the cambium. This should force the dormant bud into activity. Grafting done early in the season can be forced to grow that same season. If done in July or later should be allowed to remain dormant until the next Spring.
1) Patch bud graft: Named after the appearance of the graft. Two square or rectangular patches of identical size are cut out, one from the scion containing the bud in the center of the patch, and the other from the stock, to receive the bud patch. There needs to be a snug fit at the top and bottom of the graft, therefore it is best to construct a small template out of cardboard and trace it first before cutting in order to assure the same size cuts. Waxing or some other form of sealing is essential to prevent the graft from desiccating. One source suggested wrapping the graft with clear packing tape, and cutting a small round hole that fits over the bud. This grafting technique works better on thick-bark species.
2) T-bud graft: Named after the appearance of the grafting cuts, a T-shaped cut is made in the bark of the stock, and a bud shield is inserted into the opening. The bud shield is named such because it is shaped like a shield when cut off of the scion. Leave a leaf petiole if possible to act as a handle during the procedure. Waxing is usually unnecessary since the bark of the stock covers the graft and helps seal in moisture. The entire graft should be wrapped with grafting rubber or waxed twine, leaving only the bud unwrapped.
LAYERING: Whereas grafting techniques enhance or change the characteristics of an existing tree, layering is used primarily for propagation of additional trees from preexisting stock. The exception would be ground layering, where the nebari of the tree is ‘rebuilt’ higher up on the tree. Although there are many types of layering techniques, this paper will focus on only a few that are more appropriate to the bonsai enthusiast. Though air-layering is by far the most popular form of layering, a few different types of layering techniques will also be covered.
General information on layering: Since the main purpose of all layering techniques is to encourage the development of roots, the use of rooting hormone is encouraged in the cuts for each type of procedure listed below. Trees should be strong and healthy before attempting any layering. Don’t let flowering trees bloom while being layered as that uses valuable energy needed for the rooting process.
Tip Layering: If the lower branches are flexible enough to be bent down into the soil, then this is a fool-proof method of propagating a new plant from the parent. Pin the branch down after wounding the lower section that will be under the soil. Wire the tip of the branch up.
Air Layering: This is the most popular and versatile method of layering, as it can be applied to main trunks or side branches, and new trees can be obtained by air layering garden or nursery trees. Some trees like Pines and Junipers can take from 6 months to 2 years to layer. (However, needle junipers can root within 3 months) It is better to wait and overwinter a tree before removing the layer rather than removing it too soon before roots have developed sufficiently. Wait one year after severing the layer before major pruning, in order to allow the tree time to regain strength. Exception: If the roots are fewer than expected, reduce the foliage accordingly or else the small root system may not be able to support an abundant foliage mass. The two most popular techniques for promoting new roots are the tourniquet method , where a thick wire is tightened around the trunk or limb, where the new roots are desired, and the ring-bark method (girdling),where a complete ring of bark is removed after cutting past the cambium. The method chosen should be in accordance with the growth pattern of the tree. For faster growing trees, the tourniquet method can be used successfully. For slower growing trees, most go with the ring-bark method. For several species, there is no preference. (see list below) Trees most suited for tourniquet method (don’t use copper wire): Abies, Acer palmatum, Cedrus, Cercis, Chamaecyparis, Cornus (most), Fagus, Larix, Lonicera, Malus, Picea, Pieris, Pinus, Podocarpus, Pyrus, Quercus, Stewartia, Taxodium, Taxus, Thuja, Virburnum, Wiegela, Wisteria, Zelkova. Trees most suited for ring-bark method: Acers (most), Berberis, Buxus, Camellia, Carpinus, Cornus kousa, Corylus, Cotoneaster, Cryptomeria, Gingko, Hamamelis, Hedera, Ilex, Jasminium, Juniperus, Ligustrum, Lonicera, Morus, Magnolia, Myrtus, Parthenocissus, Punica, Pyracantha, Serissa, Syringa, Tamarix, Thea. Trees that could be air layered either way: Prunus, Azaleas and other Rhododendron, Ulmus.
To Pot or bag: If the branch is small and the tree is young, the plastic wrap method is usually sufficient. Tie the plastic wrap tightly on both ends to prevent loss of moisture. Cover the plastic loosely with aluminum foil (shiny side out) to protect it from excessive heat buildup. However, if the tree is old and/or the branch/trunk is thick, the pot method is better. It will support more roots, and will last longer than plastic wrap.
Ground Layering: A variation of air-layering, only performed further down on the main trunk in order to create a new nebari, higher on the tree. Perform the procedure like a typical air-layer. The tree can simply be potted into a deeper pot after girdling the tree and applying rooting hormone and sphagnum moss, or the procedure can be accomplished by placing a small plastic pot around the base of the tree and filled with soil after girdling the tree.
Conclusion: This has been a very short and condensed treatise on grafting and layering. Due to space constraints, many details have been omitted. The purpose of the article was to ‘whet your appetite’ and introduce the reader to the wonderful possibilities for improvements of our trees through grafting and layering techniques. Again, it is highly advised that one first practice on an inexpensive garden or nursery stock before attempting these techniques on your values trees.
Grafting and Layering (Pt. 1)