Posts Tagged ‘grafting’
At a casual glance, this photo shows a stick with a small branch. I deliberately shot from an angle that provides clues about the branch’s true nature.
I assembled some apple trees this spring, but that’s a story for another blog post. I mention it because every morning I’d check the progress of my grafts: were buds on the scions swelling? Were leaves emerging? Did the wood seem to be drying out?
One morning, I was astonished to find a small branch had appeared on one of the grafts.
For a few minutes I tried to convince myself the branch had been there all along but I hadn’t noticed it. I waffled between that explanation and the unlikely, crazy possibility that it had, indeed, grown overnight—or over the course of a few days during which my inspections had been too casual to spot it.
Eventually, the “branch” on my grafted apple tree relaxed and seemed ready to move on. This photo clearly exposes the branch to have been a well-camouflaged caterpillar—something in the inchworm family.
Then it occurred to me: my young grafted apple tree hadn’t grown a branch, it had acquired a resident. The branch was a caterpillar doing a really good job of looking like a branch.
What an awesome adaptation! Imagine you’re a caterpillar that sometimes shares trees with birds that like to eat caterpillars. One day, one of those birds perches just eight inches away! The bird sucks down several of your mostly green caterpillar neighbors, and several times it looks directly at you… but it doesn’t even lean closer because in those moments, you’re just a tree branch!
After that bad boy bird moves on, you can grab the branch with the rest of your tiny feet and inch away.
Seems to me this caterpillar had an excellent chance of growing into a moth. Apparently, even then it probably did well at avoiding moth-eating birds. The adult of this caterpillar has earthy, mottled colors on its wings so it nearly disappears when it lands on tree bark. If a bird doesn’t see you as food, it’s probably not going to eat you.
A makeshift bucket of twigs cut from pruned branches hangs in the green apple tree I’m converting into a red apple tree.
For the past many posts, Your Small Kitchen Garden has focused on grafting and pruning apple trees. Two posts back, we looked at equipment I use to graft red apple stock onto my green apple tree—and I introduced a video that shows me assembling a graft. In the last post, I listed guidelines I follow as I choose which branches will host scions in the green apple tree. This post provides written, step-by-step instructions for assembling a graft. Though I’m talking about apple trees, this technique will work on just about any deciduous fruit tree.
I’ll assume that you’ve been pruning apple trees and have several branches from which to harvest grafting stock. Make scions from last year’s growth. Last year’s growth is at the ends of the smallest branches. Last year was very dry here, so branches grew only three or four inches beyond the previous year’s growth. In wet years, my apple branches have grown a foot or more. In any case, cut and save a dozen or so twelve-inch twigs off the ends of your pruned branches, and put these in a bucket you can hang from a branch.
If there are no fruiting spurs on the section of branch you harvest, you’re probably looking at last year’s growth. If you can spot a scaly ring in the bark, it most likely marks where the terminal bud spent last winter; everything after it should be last year’s growth.
Haul the twig bucket, a gear bucket, and a pruning saw up in the tree and perch so you can easily get both hands on the host branch without falling out of the tree. I like to work on a step ladder which provides a steady base and reduces my need to climb the tree. Standing on branches erodes the bark, and increases my chances of damaging small twigs and existing grafts.
7 Steps of Grafting Apple Trees
Cut the host branch—Make as clean a cut as you can, perpendicular to the branch. Leave a stump just two or three inches long. For very thin branches (a half inch is about the thinnest it’s practical to graft onto), I might use bypass pruners or loppers, but in most cases I use a fine-toothed saw so as not to crush the branch or its bark. With a saw, cut about three quarters of the way through from one side, then remove the saw from the cut, flip it, and finish the cut from the other side. I’ve seen better pruning saws than I own cut cleanly through a branch in a few strokes without a back cut… the quality of your tools will influence your technique.
Split the host branch—Use a sharp knife, align the blade across the center of the stump, and gently rock it while pressing it into the cut end. I try to split along a line that’s perpendicular to the trunk branch from which the stump grows. For a narrow stump, make the split about and inch long. For a heavier stump, it might take a three-inch split to provide enough play to get scions into the crack.
I liked this small branch as the host for a graft; it had a gaping hole in the bark that I was able to remove, and set a graft just blow it. The bypass pruners deformed the stump a little, but I’m confident the graft will take anyway. Notice that I split the stump across the limb to which it’s attached.
Make a scion—Whittle a scion from the harvested grafting stock. Start at a leaf bud three-to-seven inches from the terminal bud of a twig. Whittle a wedge starting at that leaf bud and getting narrower toward the bottom of the scion. The wedge—from leaf bud to the end of the scion—should be about a half inch long (see photos).
Start whittling on one side of a leaf bud, but make sure you leave the bud intact. A finished scion tapers for about a half to three quarters of an inch from the bottom leaf bud down to a chisel point. The leaf bud will sit about even with the end of the stump and will point out from the side of the stump.
Insert the scion into the stump—Spring the crack open and work the whittled wedge into one side of it. The leaf bud at the top of the wedge should point out, and end up aligned with the top of the stump. I use the point of my utility knife to spring the stump open. If you do this, be cautious; when you flex it too much, the knife blade will break. For thicker host branches, I sometimes use a screwdriver to hold the crack open as I insert scions (explained in my last post, Strategies for Grafting Fruit Trees). Make sure the edges of the bark of the scion align with the edges of the bark along the crack in the host stump.
I use the tip of my utility knife to flex the stump open as I insert the first scion into the crack. The first scion usually holds the stump open enough that I can easily insert the second scion. Aligning the bark at this point is crucial.
Add a second scion—Whittle a scion to match the first one and work it into the other end of the crack in the host stump. Chances are, you won’t need to flex the crack open this time as the first scion will hold it wide enough for the second scion to fit. You may need to readjust both scions several times to make sure their bark aligns with the host stump’s bark.
Wrap the graft—I once bought and messed with grafting tape, but didn’t have any luck with it. However, while creating this series on grafting, I learned that you can coat a new graft with wax, then wrap it with grafting tape to protect it from the elements. This requires heating the wax which seems inconvenient, especially on a cold day… but I’ve never tried it, so don’t let my inexperience keep you from finding a better approach.
I use cotton twine and tree wound dressing. Tie the twine around the stump at the bottom of the crack (I use a clove hitch, but any knot will do). Then, wrap the twine around the stump, working toward the leaf buds on the scions, and laying each successive loop of twine tightly against the preceding loop. Get the last loop of twine as close to the end of the stump as you can without running it up onto the leaf buds of the scions. Finish it off by running the end of the twine through a loop, pulling it tight, and cutting off excess twine.
I tie a clove hitch at the bottom of the split, then catch the end of the twine in the first loop or two as I work my way up the stump.
Waterproof the wrap—Use a water-based tree wound dressing, and coat the cotton twine wrapping. Also, dab tree wound dressing on the end of the stump so no wood shows through. It’s ok if dressing runs into the crack and coats the bottom leaf buds on the scions; make sure you coat all the twine and the stump’s split end.
I use a water-based sealant called Treekote tree wound dressing made byWalter E Clark & Son in Orange, Connecticut. Don’t use the stuff to dress wounds left by pruning, but waterproof your graft with it to keep things from drying out while the scions knit themsleves to the host stump.
When Your Fruit Tree Grafts are Done
A successful graft wakes up more slowly than the rest of your small kitchen garden. There may be leaves on the rest of the tree for a month or longer before your scions show signs of life. Usually, the first change appears in a scion’s terminal bud; if that opens up, the graft has taken and is likely to knit up with the stump.
Once leaves emerge, remove the protective wrap from the stump. I use the razor-sharp utility knife to slice part way through the coils of twine without going as deep as the bark. This cuts through the loop of twine I tucked under at the end of the wrap and I can unravel the whole wrap from there. Unwrap gently. Sometimes the twine sticks to the tender bark; if you work slowly, you can unstick it without doing too much damage.
You’re looking at scions set in the split stump of a small branch that conveniently sprouted two seasons ago. This graft points into a space that could really use a low branch. Notice the leaf buds where the scions meet the stump. The most rapid growth occurs around leaf buds, so the design of the graft encourages the scion to grow into the stump.
It’s pruning and grafting time in my small kitchen garden, as it must be for nearly everyone in hardiness zone 6 and lower (north of zone 6). But time is running out. You should stop pruning when the leaf buds on your trees start to plump up in preparation to open, and that usually happens in early April.
My last five posts have been about grafting and pruning. I hope you’ve put the information to use. This post and the next one finish the series. This post presents my thinking about grafting onto an old established tree and the next post talks you through building a graft step-by-step. In my previous post, I described the equipment I use for grafting and introduced a video that takes you through the procedures I follow to graft red apple tree scions onto a green apple tree… so please read that one and watch the video if you want to get started immediately.
Harvesting Stock for Scions
You can harvest grafting stock all winter and store it until you’re ready to work. I harvest stock as I prune in late winter. When I can spend a half hour, I choose a problem to sort out in my red apple tree and take out a limb or two. Then I cut twelve-inch twigs off the ends of the small branches and put a bunch in a makeshift bucket.
If I have a lot of grafting to do, I focus on it almost exclusively until pruning season is drawing to a close. Then I stop grafting and make a mad dash through whatever pruning is left to do.
Graft onto Thin Branches
I like to graft onto very small branches—ones that are about a half inch in diameter. The technique, summarized, goes like this:
- Cut off the root branch and leave a stump.
- Split the stump across the middle, creating a one-to-three-inch crack.
- Whittle a scion and insert it on one end of the split.
- Whittle a second scion and insert it in the other end of the split.
- Wrap and waterproof the graft to protect it from the elements.
I’ve grafted into branches as wide as two inches across, but a branch that heavy requires one more tool than I usually carry (see box).
I cut a selected branch off square about two inches from where it attaches to the tree. I try to preserve the bark at the cut, so I use a fine-toothed saw for thicker branches, and sharp bypass pruners for thinner branches.
In an old, established tree, there may not be many conveniently-located small branches to receive grafts. This was the case with my ugly green apple tree. Knowing too little about grafting, I jumped in and started scions on large branches in poorly-chosen locations. I’d encourage you, instead, to prune your old problem trees for a season or two before you start grafting in them. Pruning encourages new growth, and in the second year, you’re likely to have many small, young candidate branches on which to graft stock from other trees.
Small Kitchen Garden Guidelines for Grafting
Here, in no particular order, are things I keep in mind as I work to convert my green apple tree into a red apple tree:
After three seasons, this graft is coming together nicely; it will probably produce fruit this season. It’s likely that this winter I’ll graft onto the branch that emerges just below the established graft.
Get the tree under control (if it’s not) by pruning according to the guidelines I presented in Prune Fruit Trees – 3: What and Why. If you’re dealing with a serious problem tree, you might put off grafting for a few seasons as you bring the tree around.
Prune before you graft. As you prune, you may need to climb your tree or at least stand on its branches. Worse, when you cut away old growth, it may fall through the branches. This activity could damage new grafts, so finish the season’s pruning on the host tree before you start grafting on it.
In a big, old tree, do lots of grafts. My grafting technique was poor when I started and I’d have about a 50% success rate. So, by doing 90 grafts in a season, I was confident I’d have 45 survivors. If you do ten grafts along a main branch and they all survive, crowding each other, you can prune some off in subsequent seasons.
Align bark. When I tell you that the bark on a scion must align with the bark in its host stump, I mean that the edges of the bark must align. The curve of the scion is tighter than that of the host stump, so the scion will bulge slightly out of the crack in which you set it.
Graft onto short stumps. Leave as little of the original wood as it practical; this reduces the chances of the host tree putting out competing branches that you’ll need to prune away later.
Graft to fill spaces. Especially on large, old trees, look for branches that come off the bottoms of larger branches, and graft onto those. Prune growth that comes off the tops of branches. This encourages the tree to develop a low profile and keep fruit within reach.
Graft to “repair” damaged branches. Sometimes, you’ll find damage on a branch you’d like to retain. Cutting the branch off behind the damage, and grafting into the shortened branch can save it while converting it to some other variety of growth.
Stay alert! Whatever knife you use for grafting needs to be extremely sharp. Don’t cut toward your body parts with it! Especially when you’re splitting a stump, don’t hold onto the stump or its parent branch. Sometimes the stump opens up and the knife slides through with little resistance. I did most of my grafting with only nine fingers one season because I got careless.
Please Chime In
Leave a note if you try grafting this season or if you have experience grafting your own plants. I’m very interested in sharing other techniques, so if you’ve tried some and want to write about them, get in touch and we can work out a guest post or a collaboration.
A new graft in my apple tree awaits warmer weather. With luck, sap will rise from the host tree into the scions and trigger vigorous growth that comingles cells from two plants, resulting in a single plant.
How about a crazy science experiment that you can do in your small kitchen garden? I’m talking about combining pieces from two organisms into a single organism that continues living and growing as if this were a natural chain of events. Make a chimera: graft fruit trees.
Grafting fruit trees is the most exotic, satisfying gardening I’ve ever done. It has extended the life of a useless tree, and nearly doubled the apples I harvest each fall.
Why I Graft
My small kitchen garden boasts six mature fruit trees: three apple, one pear, and one peach tree that came with the house, and a second peach tree we planted when the original fell over several years ago (the fallen tree still produces a good crop of peaches each summer). One of my apple trees produces delightful red apples that are great for eating and for cooking. Another produces red apples that are crisp and flavorless, though they always look great. The third tree produces green blemished, scabby apples that are mostly water and have no flavor.
Last winter’s graft looks messy, though I did remove one scion after they both started growing. As sloppy as this looks, in two more growing seasons it’s likely to smooth out, and in four or five seasons, the branch will be a consistant diameter; you won’t notice the grafting scar if you don’t look for it.
After six years of despising the green apple tree, I was ready to cut it down and make room for a replacement. I had bow saw in hand when it dawned on me: I’d always been fascinated by grafting; here was the perfect chance to try it.
Grafting is Easy
For a project that resembles the work of Doctor Frankenstein, grafting is surprisingly easy to do. It’s easiest to graft onto a tree that you’ve pruned for the past two seasons; such a tree will have young, thin branches ideal to receive scions taken from another tree.
Grafting is a late winter activity, though you can graft as long as your trees are dormant. A graft can essentially drown in sap if you assemble it while the tree is active. When terminal leaf buds become plump and ready to open, stop pruning and grafting.
As a winter project, grafting gets you outside when most people aren’t in their yards. For me it’s a quiet, contemplative time when I meet unsuspecting birds who alight before they notice there’s a human in their tree.
My homemade gear bucket holds bypass pruners, a utility knife, cotton twine, and tree wound dressing. I have a similar bucket to hold grafting stock that I carve into scions as I assemble a graft.
How to Make a Graft: Equipment
It takes me from five to ten minutes to assemble a graft. That’s long enough that I want to be comfortable while I’m working. It takes two hands, so I like to have a stable perch; I usually work on a step ladder. It provides a stable base and something to lean against or sit on depending on circumstances.
To gather stock from which to make scions, I use typical pruning gear (I wrote about it in Prune Fruit Trees – 2). I also use a retractable utility knife, a ball of cotton twine, and a container of tree wound dressing. I carry these in makeshift buckets I cut out of gallon milk jugs. Each jug has twine strung through its handle and up through its neck to encourage it to hang upright from a tree branch where I’m working.
While I’m grafting, I constantly shift gear among my bucket, my pockets, rungs on the ladder, and tree branches.
If it’s not cold in late winter, it may already be too late for grafting. Given the coldness, warm clothes are useful… but don’t wear garments you like. I’ve slopped tree wound dressing on winter coats, pants, sneakers, and gloves… tree wound dressing doesn’t wash out easily.
I’ll continue a written discussion about grafting in my next post. In the meantime, I’ve created a video that takes you through every step. The video is nine minutes and 50 seconds long, and includes close-up photos of critical issues. It’s much better information than I had when I started grafting, and it should be enough to get you going. Please watch, and check back here soon for further details and thoughts I wasn’t able to include in the video. Please enjoy:
My small kitchen garden is coming out of dormancy a few weeks too early for my taste. I usually prune my fruit trees through March, and graft from one tree onto another throughout the month. With temperatures in the first week of March going over 60 degrees Fahrenheit, I’m concerned the buds on my fruit trees will plump up, and I’ll run out of time.
At Least Prune in Your Small Kitchen Garden
Pruning is critical to the long-term health and manageability of your fruit trees, so get it done before the sap runs. By pruning while the tree is dormant, you give the exposed green wood a chance to dry out before sap is moving through it. Just a few days’ drying is enough to seal a wound and keep it from leaking sap that could attract insects and nurture molds and microorganisms.
My past three posts have been about pruning, and I’m putting together a post about grafting. While working on these, I found a most curious growth in one of my apple trees and thought I’d share it.
A branch emerges from the trunk near the bottom-left of the photo and runs diagonally up and right. Where it crosses another branch, the two have grown together. Grafting exploits this natural malleability, letting you easily attach branches from one tree to another where they bond to their new home.
Apparently, two seasons ago a young branch rested in the crotch of a second young branch. Even though I had attempted some grafts on the same trunk, I hadn’t noticed this crossing of existing branches; in my series on pruning, I encourage you to eliminate such crossings to prevent damage to bark and competition for light.
As you can see in the photo, the two branches have grown together. I have no use for either branch—this is a tree that, through grafting, I’m converting from a green apple tree into a red apple tree (I’ll explain in my next post). Both branches are green apple tree stock. Because of their novelty, I may leave them, though I’d rather all the tree’s energy went into producing red apples.
I’m on a mission to plant a pear tree this fall in my small kitchen garden. In the past week, I’ve visited or contacted garden stores and nurseries within a half hour drive of where I live in central Pennsylvania—hardiness zone 5b. I’m ready now to concede that the local culture simply doesn’t believe in fall planting of perennials. That’s too bad for two reasons:
- Planting in the fall has many advantages (read about them here)
- I’m going to have to mail order my pear tree
What I’d Look for at a Nursery
As I explained in my last post (click here to read it): Were I there to choose the tree in person, it would have a straight trunk running vertically up to a healthy leader—with, perhaps, a bump where the leader was grafted onto root stock. I would not buy a young tree whose main trunk made an abrupt change in direction, or had one dominant branch that was obviously thicker and reached higher than the main leader. I’d also be cautious of the distribution of branches.
Sometimes, it seems nursery operators prize low branches. Young trees often come with branches starting within a foot of the ground which is not a problem unless the tree’s main trunk makes an awkward diversion from vertical. When a tree has a vertical leader, within a few seasons, you can prune away the very low branches, and encourage growth on the higher ones.
However, when a young tree’s leader is at the end of a horizontal branch nearly as thick as the main trunk, it may take many years of aggressive pruning to train a new vertical leader that’s even vaguely in line with the trunk. If you’re growing a very small tree, then low branches make sense. But I want to be able to duck under my tree’s branches, so it won’t do to buy one that a nursery assembled with one or more main branches three feet off the ground.
It’s about Assembly at the Nursery
When you’re shopping for fruit trees, chances are you’re looking at chimeras. A chimera is an organism assembled from parts of several organisms. Especially in the cases of dwarf fruit trees, but often with larger trees as well, a nursery worker, through a craft called grafting, has combined two or more types of trees to make a single tree. The worker cuts a scion (a thin branch with several leaf buds and a leader at its tip), from a standard variety of fruit tree—say, a Bartlett pear. The worker also roots a variety of pear tree that has specific desirable characteristics, but that may produce unappealing fruit. The worker preserves the roots and cuts off most of the above-ground leader, replacing it with the Bartlett pear scion.
Over the course of a few months, the select root stock melds with the scion, and new wood and bark grow together to make a viable tree. The nursery worker makes sure no leaf buds survive on the root stock, so the only viable growth above ground is the good-eating variety of fruit.
Why the Grafting?
In grafting, the nursery worker is creating a tree with the best possible combination of features. Often, a desirable fruit’s roots are vulnerable to diseases, but the rest of the plant is hardy. It makes sense, then, to graft the desirable fruit onto a different root that won’t succumb to disease.
To make dwarf fruit trees, a nursery worker selects a “dwarfing root stock,” and grafts a desirable fruit onto it. The dwarfing stock simply passes water and nutrients to the rest of the plant more slowly than the plant would like… acting, in effect, like a bonsai tree master who cuts roots off of plants so they’ll grow up small though proportioned just like normally-grown trees.
Grafting can result in trees with undesirable shapes—especially when the nursery grafts two or more scions onto a single root stock (this is advantageous for fruits that require cross-pollination and is also necessary if you want two or more varieties of fruit from a single plant). Only one scion can be the tree’s leader… others must be branches—and when you graft a branch onto a three-foot tree, you have a tree that wants to be in your way when you do yard work.
What’s my Next Step?
I want to order my new pear tree soon so I can add it to my small kitchen garden in October. I’ll browse on-line nurseries, make a list, and share it with you in an upcoming post. When I select a nursery, I’ll explain why. I’ll also order a tree and explain my thinking about it.