Grafting Honeylocust is easy to do. Here are the instructions for a dependable method. First a little background.
Animal clones are in the news, but people have propagated and made use of plant clones for all of recorded history and probably since their earliest agricultural efforts. A plant clone is a set of genetically identical individuals. New members of plant clones are created by vegetative propagation, that is taking a part of an existing plant and getting it to grow into a new plant. Roots, stems, leaves, buds, twigs, bark and other parts of plants have been grown into new plants. Which parts and what methods are used to get the parts to grow vary from plant to plant. Plants grown from seed are not part of a clone because the polination of flowers produces a unique genetic makeup for each seed (and resulting plant).
The reason plants are cloned is to get a uniform result. The result may be quality of the fruit, or color of the folage, flowers produced, or the nutritional value of Honeylocust pods. Although individual plants in a clone are genetically identical the results produced (flowers, fruit ect.) by each individual will also be affected by the climate, soil and care received by that individual.
Grafting is taking part of one plant and attaching it to another plant so that the two parts will grow together as one plant. There are many methods for grafting trees. Quantities of a clone are often produced by grafting a part (twig or bud) from the clone onto a rootstock (2 to 3 foot tall, 1 to 3 year old tree grown from seed) then pruning the tree so that all of the above ground part of the tree grows from the graft. Hardy (nothern grown) Honeylocust seedlings are the best rootstock for grafting selected Honeylocust clones.
When you find (or create from careful selective polination) that excellent Honeylocust tree here is an easy method to turn that one Honeylocust tree into a clone of many genetically identical trees. This method also works well on plums and requires no grafting wax or wraping if grafts. One sharp knife and a pruning shears is the equipment required. This is not new and probably is one of the oldest grafting methods known.
First, growing the rootstock. In the nursery business young seedling trees are called whips or liners. Two to three foot Honeylocust liners are about one half inch in diameter at ground level and will be just right for grafting after one years growth in your nursery. A few may be purchased from retail nurserys for $2.00 to $3.00 each. Wholesale nurserys only sell larger quantities (minimum 300 or more) for lower prices (30 to 50 cents each). If dealing with a wholesale nursery get #1 plants and order in October or November for delivery the next March or April. A note on growing your own root stock: Honeylocust seedlings are easy to grow except for the seed germaniation rate. The seeds want to germinate only after passing through the digestive tract of an animal. (Ponder the advantages of that trait to a tree producing large quantities of seed.) This may be simulated by soaking the seeds in hot (not boiling) water or by nicking (making a break in the seed coat with a file or other tool) and then soaking. Buying good uniform stock is worth the modest price.
Soil needs to be good agricultural soil. Not to sandy, not heavy clay. The surface soil must retain moisture so that the grafts do not dry out. Honeylocust trees will grow on many soil types, but getting things started in the grafting nursery requires good soil.
Plant the liners one or two inches deeper than they were growing in the nursery (look for the ground line on the plants). Spacing depends on what type of cultiviting (machinery) you are using and how much space you have. In a small space with hand cultivating, liners for grafting may be planted 12 inches apart in the row with rows three and a half feet apart. More space makes work easier. Plants 2 feet apart with rows 6 feet apart allows small machinery for cultivating and room for the grafted trees to grow for two or three years. Planting the liners (rootstock) in the final location for the trees and grafting them in place is usually not a good idea, because your grafting success will not be 100% and the grafted trees from your nursery will transplant easily.
Liners are planted in the spring, grown for one year, then grafted, grown for one year more and may be sold or planted as three to five foot trees in the spring two years after planting the liners. Honeylocust trees transplant easily so the grafted trees may be left in the nursery for two or three years if there is room.
Second, how to crown graft Honeylocust. It is easy to say graft in the second week of April but this will vary depending on your location and the personality of the spring. Graft at (or just before) the first sign of swelling of the rootstock buds. The twigs you are going to graft onto the rootstock are called cions (pronounced cy - ons). The cions come from a tree that you want to clone. The best cions are from last years healthy new growth 1/8 to 3/8 inch diameter. Second years growth is usable if it is all you have. One gallon heavy duty ziplock plastic freezer bags are an excellent place to store cions so cut them a little less than that length with a sharp pruning shears. Make your cuts just (1/4 to 1/2 in) above the bud nodes. The cions should be cut when they are completely dormant but not frozen. Mid March to early April in Minnesota, most years. Seal the bags (remove air) and store in the refrigerator (not freezer) till grafting time. A bit of slightly damp paper towel may keep the cions moist.
Finally grafting day has arrived ! Tools you need are a sharp (very sharp) knife. I use a Chicago Cutlery 96N6. This is a 6 inch blade, curved knife and is easy to control. Pruning shears (I use a sharp lopping shears) is used to cut off the stocks. Dig (with your hands or a trowel) around the base of the root stock so you expose 2 to 3 inches of trunk (you did plant them deeper didn't you?). Gently wipe the dirt off the stock with a paper towel. Cut the rootstock off square, at or just below the surface of the ground using the pruning shears. Use the knife to cut on a diameter, 1 to 1 1/2 inches down into the stock. Use steady pressure and a slight rocking motion. The idea is to produce a cut not a split in the stock, it must spring strongly back together. If you go to far and cut the stock in half it is ruined, go on to the next one.
Preparing and placing a cion is the most exacting part of the grafting processes. Cut (with the pruning shears) a 4 to 6 inch cion with a bud near (1/2 to 1 inch) the top (top is the end nearer the end of the branch). There should be no bud 1 to 2 inches from the bottom end. Use the knife to cut the bottom end of the cion to a wedge. Cut on two sides starting about 3/4 inch from the end. The wedge should taper evenly to the end of the cion and also from one side of the cion to the other. The wider side of the wedge is the part that will heal (graft) with the stock so be careful not to disturb the bark. This is where a very sharp knife is required.
Look at the stock to decide which end of the cut the cion is going to be placed in. Choose the end where the bark was not disturbed by the cut and any curve of the stock matches a curve of the cion. Gently slide the knife down into the cut on the end opposite where the cion is going to be placed. Use the knife to pry open the cut in the stock just enought so the wedge on the cion may be placed in the opening. Place the wedge in the stock so the cambium layers on the stock and cion are in contact over as large an area as possible. Do not push the cion into the stock. When the cion is placed correctly release the knife and let the stock spring back to hold the cion in place. No wraping or grafting wax is required. Any movement of the cion will ruin the graft. Carefully place and firm the fine, loose, moist soil around the stock and cion. The top bud on the cion should be about 1 inch above the surface.
Third, caring for the grafts in the nursery. Keep the soil moist but not soggy. Mulching is good but not necessary, don't cover the cions with mulch. Of course the grafts must be in a protected area where animal and people traffic does not occur. When the grafts start to grow they are rabbits favorite food. A 2 foot Tubex tree shelter (or cut 2 foot tubex in half for 1 foot) gently placed over each graft will help.
Review. The critical parts of the process are;
1. Is the soil good. Light soil that stays moist (has organic matter).
2. Did you plant the stocks at the right depth. 1 to 2 inches deeper than they were growing.
3. Get a good match of the cambium layers at the graft. The cambium is the thin green line at the inner edge of the bark, just outside the wood. It is the only part of the tree trunk that actually creates new growth, therefore the only part that will graft.
4. Do each graft calmly but quickly so the freshly cut surfaces do not dry out.
5. Keep the soil moist.
6. Protect new growth from deer and rabbits (may be the most difficult
part).
50% success is good for your first try. 90% is possible if everything
is right. If the stocks made good growth then your grafts should all be
3 to 5 feet tall at the end of the first season. Happy grafting !