Providence Farm Ornamentals propagates numerous varieties of Japanese maples and dwarf conifers by grafting. Grafting involves attaching a plant cutting (scion) with a predictable and desirable characteristic, to a compatible rootstock. Many of these ornamental plants are difficult or impossible to propagate by other methods. The following is a step by step description of the process used to generate grafts at Providence Farm Ornamentals. In this demonstration you will see pictures of 3 grafts being produced. I use the same technique for all the grafts with only slight variations.
To begin grafting it is necessary to acquire a suitable rootstock that is compatible with the plant you are trying to graft. Rootstocks of a suitable size are acquired in early spring and planted in tree band containers. These are small narrow containers that have mostly open bottoms to allow for good drainage. The 9 inch tree band containers I use help avoid knotted root masses, and generally produce a superior graft because of the well developed root system. After rootstocks are planted they are grown for a season in the tree band containers, and allowed to go dormant as winter arrives. Starting in early January, dormant rootstocks are brought into a heated greenhouse to gradually wake up the plant. Grafting can commence once the rootstocks are showing signs of breaking dormancy.
Conifers will show signs of new white roots extending from the bottoms of the containers. Japanese maples will have dormant buds beginning to swell. At this point, it is time to collect scions from plants you wish to propagate. I propagate my own stock plants, use stock from local private collections, as well as have scions shipped in from arboretums and established private collections in other parts of the country. It would be ideal to collect and graft while the scions are freshly cut, but they can be stored in a zip lock bag in the refrigerator with just a trace of humidity present in the bag.
When collecting scions from my own stock plants I select vigorous growth. For this demonstration I am going to graft an Acer palmatum ‘Sango kaku’ to an Acer palmatum rootstock. I will also graft a Pinus densiflora ‘Tanyosho Compacta’ onto a Pinus thunbergii rootstock. The final graft I will do is a Pinus parviflora ‘Pygmy yatsubusa’ attached to a Pinus strobus rootstock.
Now that I have my scions collected I will go to the greenhouse and get started. I will begin by cutting the top the Acer palmatum rootstocks to about 12 inches tall to make it easier to handle.
With a sharp clean grafting knife I prepare to make the first cut on the scion. The back of a grafting knife is perfectly flat with a sharpened bevel on the opposite side. This flat edge is important to create two clean flat surfaces to mate to the cut made in the rootstock. Having a sharp blade ensures that the cambium layer in the bark is not damaged. Lining up the cambium layer on the rootstock and scion is the goal of the grafting process.
I’ll do the entire process with the Acer palmatum ‘Sango kaku’ first. I begin by selecting a section of scion wood from the stock plant with 4 strong healthy buds.
With a firm grip on the scion, I visualize the first of two cuts I will make. With a quick pull of the knife, and a little luck, I will end up with a nice flat surface on the scion.
I lay my grafting knife up to the cut and determine if the cut was successful. After that I will roll the scion in my hand 180 degrees, and make similar cut on opposite side creating a wedge shape that will tuck into the cut created on the rootstock.
The next step is to make a slice in the rootstock to receive the scion. I find it easier to make the scion cuts first to determine the length of the slice that needs to be made in the rootstock. The rootstock cut is slower and easier to control. Making the length of the cut closely match the scion allows for a tight mating surface that will stay in place while the budding strip is applied.
I got a good fit on this one, so it is time to secure the scion to the rootstock with a budding strip. Care must be taken not to shift the scions while applying the strip.
This next step is optional. For my grafts, I like to press a small piece of oil based clay in the space at the very top of the budding strip. This limits any of the tree wound product (which I use to seal the graft) from dripping down in to the graft cuts.
Now I am going to apply a product intended for tree wounds. This product will seal the grafted area and keep the mating surfaces from drying out while they are knitting together.
The graft below is a different graft but shows how a finished Acer palmatum graft will look. Notice that there is a dab of sealant at the top of the scion to keep it from drying out. At this point the scion is meshed with a strong viable rootstock, and sealed from drying in all areas that have but cut.
The finished graft is now maintained in a greenhouse as the graft union knits together. The greenhouse is held at a minimum of 45 degrees, and a maximum of 75 degrees. The grafts are also shielded from direct sun with a shade fabric.
After several weeks the scion’s new growth begins to emerge. As the scion growth gets stronger, I will begin to cut the flushes of growth that sprout from the rootstocks, until I remove the entire rootstock towards the middle of the summer.
I’ll do a couple of pine grafts now. They are completed in much the same way as the Japanese maple. I will start with the Pinus densiflora ‘Tanyosho compacta’ scion that was taken earlier, and a Pinus thunbergii rootstock. I will top the pine, removing the dominant buds, but leaving some needles.
Wedge cuts to the scion will be made the same as the maple.
Now I slice the rootstock to accept the wedged scion.
The scion is tucked into the rootstock.
The scion and rootstock are bound together with the budding strip.
The graft gets sealed. Many grafters do not bother to seal conifer grafts, but I feel I get more reliable results and it is worth the extra effort.
One of the main differences when grafting conifers is the need for a humidity tent to keep the scions viable while the surfaces are knitting together. This tent needs to be shaded from direct sun to avoid overheating. The grafts need to stay cool and moist during this period.
The grafts need to stay in this tent for approximately 6 weeks. It is important to check on them regularly. As the scions’ candles begin to show signs of elongation, it is time to remove them from the tent and gradually harden them off.
Next, I am going to graft the Pinus parviflora ‘Pygmy yatsubusa’ to a Pinus strobus rootstock. I’ll check the bottom of the rootstock to make sure I see some new white roots emerging, showing that the rootstock is "waking up" from winter dormancy. I’ll cut off the dominant buds on the rootstock, leaving some needles.
Pinus parviflora ‘Pygmy yatsubusa’ is a dwarf form of Japanese white pine, and has needles covering most of the scion wood collected. To prepare the scion, I will need to trim some of these needles off the base of the scion to clean up an area big enough to make my wedge cuts.
The wedge cut is made to the prepared scion, and tucked into the slice on the Pinus strobus rootstock.
All conifers have sap as you make your cuts. It is a good idea to keep rubbing alcohol close by for cleaning your blade occasionally. Needle removal and sap on conifers make them more difficult to graft in some ways, but the wood is much softer compared to Japanese maples and creating a flat surface on the wedge cuts is not as critical. They are slightly pliable and can be pulled in a bit with the budding strip to deal with slight inconsistencies. This graft will also go in the humidity tent until the scions buds are showing signs of growing.
Many conifers can be propagated by grafting. Below are named Fir cultivars grafted to Abies firma rootstocks, and spruce cultivars grafted to picea abies rootstocks.
I hope this demonstration was informative. It is easy to see that the process of grafting Japanese maples and dwarf conifers is not difficult, but does take some time and experience to achieve a quality graft. At Providence Farm Ornamentals I focus on quality not volume in every aspect of the production process. I would be happy to answer any questions you may have about my production methods. You may call me at 336-998-9758 if you need additional information.Carl Weston