Grafting is a challenging gardening technique. It involves taking two different varieties of a particular plant and joining them together to create new ‘Frankenstein’ plants that may perform better. If you are looking for a new challenge in your polytunnel garden, grafting your own fruit trees and other plants could be something to consider.
What Is Grafting Used For?
Fruit trees are often grafted onto rootstocks to affect vigour and size. Most of the fruit trees that you will buy for your garden will be ‘Frankenstein’ plants. They will combine the scion top sections, with certain fruiting characteristics, with rootstocks of a different variety that are selected to produce trees of a certain size, or with specific growth characteristics.
Interestingly, grafting plants in your vegetable garden could also bring benefits. Grafting edible could be beneficial in a range of ways. It can:
- Increase the vigour of the plants.
- To improve resistance to low temperatures.
- Provide better resistance to soil borne pests and diseases.
- Make it possible to grow plants in the same place year after year. (Useful in a greenhouse or polytunnel bed, for example, where crop rotation is challenging to practice.)
- The potential for earlier, heavier crops from certain plants (such as tomatoes).
Grafting Fruit Trees
Which Fruit Trees Could Be Grafted?
Grafting is suitable for a range of fruiting trees. Fruit trees grown on rootstocks in the UK include:
- apple trees
- pear and quince trees
- plum, damson and gage trees
- cherry trees
- apricot & peach trees
- citrus trees
Which Rootstocks are used?
Apple Tree Rootstocks
MM106 is the most popular apple tree rootstock. It creates semi-dwarfing trees around 4m high when bush trained. Those who wish for even smaller trees can opt for the M9 and M26 rootstocks, which are true dwarfing types. These create trees around 2.4-4m high when bush trained. For larger apple trees, MM111 is a vigorous type, creating trees around 4-4.5m tall, and MM25 is very vigorous and trees wll reach a height of around 4.5m.
Pear Tree Rootstocks
Pears are often grown on quince rootstock to restrict growth. Quince C is a dwarfing rootstock that will create small trees of around 2.5-3m in height. Quince A is semi vigorous and will create pear trees of around 3-4.5m in height.
Plum, Gage and Damson Rootstocks
Plums and related fruit trees are often grown on a Pixy rootstock to reduce their eventual size. These rootstocks create a tree with an ultimate height of 3-4m when bush trained. These fruits are also sometimes grown on semi-vigorous Torinel and Saint Julian A – which will create trees with an ultimate height of 2.4-3m and 4.5-5m respectively.
Peach, Apricot and Nectarine Rootstocks
Torinel and Saint Julian A are also often used as rootstocks for peaches, apricot and nectarine trees for UK gardens.
Cherry trees are grown as patio or container trees are often on a Gisela 5 or G5 rootstock. This is suitable for bush, pyramid or fan trained trees and will create trees with an ultimate height of around 2.4-3m. For somewhat larger trees, Colt rootstock is chosen. This is a semi-vigorous type that will create trees that reach an eventual height of around 6m.
Citrus Tree Rootstocks
Citrus trees are often grafted onto dwarfing rootstocks, so that they can be container grown and brought under cover or inside during the winter months here in the UK. There are also other rootstocks to consider that will make citrus trees better suited to UK growing. For example, trees grafted on to P. trifoliata rootstock have increased cold tolerance.
How To Go About Grafting Fruit Trees
Most fruit trees will already come ready grafted. However, if you wish to take on a new gardening challenge and go about grafting your own fruit trees, you can do so by side-splice grafting in the spring or autumn.
Side Splice Grafting
- Select healthy, two-year old scions and rootstock trees,ideally around pencil thickness.
- Wash hands and tools, selecting a good,sharp implement to make your cuts.
- Cut the scion just about a bud until 15-25cm lengths.
- Cut the rootstock down to around 7.5cm.
- Make a downward nick around 3cm below the top of your rootstock.
- Starting at the top of the rootstock, make a downward, sloping cut to meet this first cut and remove the sliver of wood.
- Repeat this process on the base of the scion, cutting of a sliver of the same length as on the rootstock. Try to make straight cuts to the scion and rootstock fit snugly.
- Fit the base of the scion into the rootstock so that the cambiums (the thin green layers beneath the bark) meet, ideally on both sides of the stem, but it is usually satisfactory if they do meet on only one side.
- Wrap the graft with grafting tape or raffia, and coat any exposed cut surfaces with grafting wax.
- Place your grafted fruit tree under cover in a propagator or greenhouse. Keep compost moist but do not over water and you should see new growth,if the graft has been successful, in around 6-8 weeks.
Whip and Tongue Grafting
You can also graft some fruit trees using another grafting technique known as whip and tongue grafting. To do so:
- In December or January, take strong,healthy,vigorous shoots from a 12 month old scion and rootstock of approximately the same diameter. (Ideally around 2.5cm).
- Remove a 23cm length from the scion tree, cutting just above a bud.
- Heel scion lengths into a well-drained, sheltered site leaving 5-7.5cm showing above soil level to keep them moist but dormant,or keep them wrapped up in the fridge until spring.
- In February, before bud break, cut the top off the rootstock at about 15-30cm above soil level and trim off side shoots.
- Make an upward facing cut of 3.5cm on one side of the rootstock, that exits halfway through the stem, and another downwards facing cut one third of the way down the exposed face of the first cut. This should be around ½ cm deep.
- Next, take the scion (three to four buds long) and create a corresponding ‘tongue’ on it by making a flat, sloping cut 5cm long just behind a bud, and an upward cut ½ cm deep.
- Bring the scion and rootstock together so that the ‘tongues’ interlock.
- Match the two cambiums together as well as possible.
- Bind firmly with grafting tape or raffia and remove this around 8 weeks later,once a callus has formed and the grafting has taken.
Grafting Vegetables & Other Plants
Which Fruits/ Vegetables Could be Grafted?
Plants common to grow your own gardens that could be grafted include:
- sweet peppers
Which Rootstocks are used?
Rootstocks for tomatoes and other Solanaceae are tomato F1 Aegis and Estamino F1.
The most common rootstock for Curcurbitaceae that is available to home gardeners is ‘Triumph’.
When to Graft
Rootstocks and scions should be sown from seed in the late winter or spring. (Scions and rootstocks will grow at different speeds and so it is important to consult suppliers for exact sowing requirements.)
Plants are ready for grafting when they are at least 10cm tall and have a good stem. Ideally, both rootstock and scion plants should have stems of similar thickness and size.
How to Go About Grafting Plants
- Wash your hands thoroughly before working with the plants.
- Gather the things you will need: a very sharp, sterilised scalpel or razor blade, grafting clips or Sellotape, a clear plastic bag or propagator.
- (For wedge grafting) Cut off the upper portion of the rootstock plant and make a vertical slit up to 1cm long in the top of the stem of the lower portion.
- Cut off the lower portion of the scion plant. Slice the base of the upper portion of the scion plant into a V shape.
- Insert the scion upper portion into the slit in the rootstock lower portion.
- Secure the two halves with a grafting clip or Sellotape.
- Straight away, cover the grafted plant with a plastic bag or propagator and keep it at 15-19 degrees C, out of direct sunlight.
- Each day, uncover to air your grafted plant and water to keep moist but not wet.
- Once the graft union has calloused and your plant is growing strongly (which should take around 2-3 weeks), remove all grafting clips or Sellotape.
This method is called wedge grafting and is the simplest and most straightforward grafting method. Though there are some other grafting techniques that you could also consider, this is generally the best choice for those new to grafting.
Do you have any tips or comments to share? Feel free to share your grafting suggestions in the comments below.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.