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Grafting Japanese Maples Without Greenhouse

(Last Updated On: February 27, 2022)

Grafting Japanese Maples Without a Greenhouse

No greenhouse around here

Grafting Japanese Maples without a greenhouse is possible. Humidity is needed to keep the moisture level up at the graft joint.

Greenhouses have that level of humidity that makes successful grafts possible. But, humidity levels can be maintained without using a greenhouse.

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Tools and Accessories

The first thing to consider is cleanliness. Alcohol is used to wipe down everything during grafting. Knife, tree, and scion. This is a very, very important step to prevent any germs from getting into the new graft.

Grafting requires a very, very, very sharp knife.

grafting knife
Special grafting knife

There are actually specialty knives you can buy just for grafting. Some people use razor blades or box cutters with razor blades.

Since you are using such a sharp blade, some protection should be applied to your most vulnerable fingers. A heavy wrap of tape around your thumb is well advised.

Rubber bands or tape??

The graft joint needs to be held together tightly while it heals together. This can be accomplished by either rubber bands or special stretchy grafting tape. I prefer the tape myself, but either will work.

stretchy grafting tape
Stretchy grafting tape

There is a special grafting wax that you can buy to cover and seal the joint after it has been taped or banded. This is melted at a low heat and applied all around the joint using a small brush.

grafting wax
Grafting wax

Here is the magic ingredient for success in the house

Plastic bags that fit over the grafted tree. Large plastic bags like bread bags work well.

Make sure they are clean. **Big hint** Turn them inside out first. I learned the hard way about mold and disaster in a bread bag. Clear bags are ideal because they are easier to see what’s going on inside.

Warm up the rootstock

If you don’t have a greenhouse but you want to try grafting some special rare Japanese Maples, don’t despair. Grafting is done during the winter while the trees are dormant.

The rootstock (green or red Japanese Maple seedling) is brought into the house or warmer area to warm it up and make it start to come out of dormancy.

Here come the buds

Once the buds start to show some new growth, it is time to start grafting. This means the juices are flowing inside the tree.

These juices are what need to be diverted into the scion you are adding to create the new variety that you want. These rare and special varieties need that strong root system to grow on.

Gather your scions

Now is when you go outside and cut some scion pieces from your special Japanese Maple trees. Scions are nothing more than a section of recent season growth from the tree you want to duplicate or propagate. Make sure you keep the variety names labeled and separate, they all look alike now.

Try to use a diameter similar to the rootstock if possible. They need to still be dormant. If you have to buy in scion material, it should be kept moist in the refrigerator until now. You want to use a manageable size piece, at least a few nodes long.

Japanese Maple scion
Japanese Maple scion

Cutting time

Here is where your sharp knife comes in.

You want to make a straight slicing cut down along the trunk that just gets under the bark into what is known as the cambium layer. That is where all the life flows in that little tree.

This cut needs to be flat and shallow in depth and have a smooth edge, no fuzziness or jagged edges. This will be the joint line between the two parts and they have to match smoothly.

cut into rootstock

Time for a wedgie

Now for cutting the scion into a matching wedge shape. You want a clean cut on each side of the scion coming to a sharp point. No fuzzy or jagged edges.

wedge cut on scion
Sharp, wedged point

2 become 1

Insert the scion into the cut on the rootstock. The scion should fit snugly without forcing.

At least one edge should match up flat and smooth with the cambium layers of both, lining up outside and inside. You want no gap between the 2 parts or else the joint will fail. Recut if you aren’t satisfied with the union.

Wrap it up

Once you are satisfied with the line-up, it is time to wrap it up tight. Whether you use rubber bands or the stretchy tape, make sure the joint stays in place while you wrap.

wrapped graft joint
Joint wrapped up tight

A light coating of the warm wax will seal it up.

Plastic bag time

Wintertime inside a house is very dry because of the heat to keep us warm. To overcome this and provide the necessary humidity or moisture to heal the joint, water the potted tree.

Now gently place the plastic bag over the tree and new graft and down over the top of the pot. A rubber band is used to hold the bag securely around the pot and keep it in place.

bag secured around pot
Covered with a plastic bag

Another option I’m trying

I am now using a couple of those cheap, small clear plastic greenhouses in the house. They stand about 4 feet tall and are about 26 inches in width. They are just 12 inches deep and have several shelves.

The clear plastic covering goes to the floor and has a zippered door. I have a boot tray underneath them so no water will reach the floor.

By being totally enclosed, the moisture from the trees should condense on the inside providing the grafts with a humid environment because of the warmer air on the outside.

Look for droplets

After a short period of time, a day or so, tiny water droplets will appear on the inside of the bag. This is telling you that inside the bag is cooler than your heated air and it is forming condensation. This is providing the humidity necessary for success.

condensation inside bag
Tiny water droplets forming

Don’t overdo it though

Moisture is needed but too much can be bad.

You want the juices flowing up and into the scion but you want that slow and gently. Too much water and the juices can actually flow so much that they “blow out” the scion before it heals in.

A little light will help in the natural healing process and before long the buds on the scion should start to grow. I like to move my grafts closer to a window for some sunlight.

Keep an eye on the moisture inside the bag. If it drys out, water it a little bit.

grafted trees getting some sunlight
Pots near a window

Leaves, leaves, leaves

The scion has started to grow its own leaves, and you notice more condensation forming inside the bag.

scion growing new leaves
New leaves are forming

A light misting of a fungicide inside will help prevent problems.

The graft is still too tender to remove the bag, trust me, I found this out the hard way. Do not remove the bag, even if there are several nice leaves growing.

The leaves can be forming from stored energy in the scion. Removing the bag will expose the graft to the warm drying air inside the house. Been there and done that too. Failure is the result.

Out they go

By this time, enough time has passed that you should be approaching safe temperatures outside. You can start taking your pet grafts outside for short periods to get acclimated to the outdoors.

Gentle shade for extended times will help them tremendously. While outside, the bags can be removed.

The bag goes back on when they come back into the house. I do this for longer and longer periods and before long they stay out the whole time. I keep them in a protected area out of direct sunlight and make sure the night time temperature stays well above freezing.

On their own

Now that the graft has been growing on its own and doing well, it is time to remove the rest of the tree. I cut the tree off about an inch above the graft so all the energy goes to the graft.

It is now becoming the special variety that you grafted. Make sure no new growth appears below the graft union.

Final cut

It is now in the late spring/early summer and I will trim the tree down to just above the graft so that the tree will naturally heal over the area. This now completes the cycle of grafting Japanese Maples without a greenhouse.

Grafting fruit trees is similar. To find out more about Growing Fruit Trees, check this out.

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