When there’s something wrong with the roots of a tree, it can feel like a hopeless situation. There’s not a lot you can do to manipulate or help the thick, buried, powerful roots of a tree, and yet we all know how crucial they are to plant health.
Inarching is one of the few ways you can help restore healthy roots to a tree, by sort of sticking new roots onto the old tree. It’s a bizarre idea that I’d never come up with on my own, but that’s why learning from seasoned orchardists is so worthwhile.
When to Use Inarching
- You damaged your root system. Perhaps you had to cut some major roots for construction. That side of the tree will show signs of decline, but inarch grafting new rootstock to that side may help the problem.
- To bridge a low wound, such as from rodent or mechanical damage. If the wound is very low, near the root flare, you’ll have an easier time doing an inarch graft than a bridge graft.
- You need to put a new rootstock on an old plant. If you are a pretty advanced fruit grower, you might find that a faster-growing or more soil-suited rootstock is available for your fruit tree. Inarching lets you connect the new stock to your plant.
- Dormancy. Inarching is done outside of the growing season. Remember that if you need to plant saplings near your tree, that is hard to do when the ground is frozen, so you can and perhaps should prepare to inarch with sapling plantings a season or more before doing the actual graft.
What You Will Need
- Young compatible saplings and the ability to plant them near the tree, or suckers near to the trunk. You can plant these a season or years before you do the graft, to let the saplings establish and grow strong roots.
- A grafting knife.
- A chisel and mallet, possibly.
- A bow saw, possibly.
- Long nails and a hammer.
- Sealing wax.
Making the Inarch Graft
- Trim any wound edges to a cleanly cut and smooth edge, removing all ragged and dead tissue. If you are not inarching over a wound you can skip this step.
- Plant or select appropriate rootstock near the tree. You’ll need plants growing very close to your tree trunk with flexible stems, though their thickness can vary. To get these, you’ll either need to plant an appropriate species near the tree, root cuttings near the tree, or use suckers of the tree itself in the inarch.
- Cut long slits in the bark above the wound or at an appropriate low place on the trunk. Cut pairs of slits distanced at the exact width of the rootstock stem. These slits should allow you to pry up a free end of bark to get underneath it. You should leave a strong flap of bark at the top to pin in the stock, but remove as long a strip of bark as is needed to allow contact between all parts of the stock that can be made to touch the trunk.
- Cut the roostock to length and slice off its inside. The stock is to be just long enough to be bent into the slit. Cut it on a slant, slanting upwards towards the trunk, so that the long side of the stock is against the trunk. Then make a long, vertical slice off the inside of the stock, making it about half as thick. A flat exposed face now faces towards the trunk.
- Force the pointed top of the scion under the slit bark, and have the exposed trunk and stock faces make close contact. To work it in, pry up the slit bark—possibly with a chisel. The scion is now firmly fixed in place by the tension of the bark flap. Drive nails into the stock and trunk to hold them tight together, no face exposed. The nails pass through the bark flap, through the piece of stock, and into the trunk wood.
- Repeat step five all around the tree, joining each stock into the trunk.
- Wax all of the unions and the exposed wound wood. Perform standard aftercare.
Hartmann, Hudson T. and Dale E. Kester. Plant Propagation Principles and Practices, 7 ed. 2002.