Grafting joins the roots of one tree with the branch of another, and bringing two trees together into one can give you the best of both.
Sheryn Clothier’s tips on grafting trees
It is the rootstock that determines how the tree grows. It decides how tall it gets, how it branches, what soils and climate it likes, how soon it will produce fruit, the quality of the fruit and what pests and diseases it will resist.
The scion (which contributed the branch to the partnership) decides what type of fruit it will produce, so a good fruit can be replicated exactly.
Just about every fruit tree you buy is a grafted tree.
And a good nursery will tell you what the rootstock is.
Except for lemons, most of our citrus is grafted onto Poncirus trifoliata rootstock. Trifoliata is resistant to the citrus tristeza virus that has been the death of millions of citrus all over the world. It is also cold hardy (in citrus terms, New Zealand is cold) and produces large amounts of high quality fruit. Trifoliata is also semi-dwarfing – the tree does eventually get to full height, but it takes longer to get there.
Peaches, nectarines and apricots are often grafted onto pre-grown stones so they fruit sooner, but I suggest these trees are best grown from seed. I find that the stone-grown trees are very similar to their parent, and a seedling will start producing fruit when about four years old.
Plums are usually either on Myrobalan (vigorous and tolerates heavy soils) or Mariana (dwarfing) roots but once again, seed-grown or cutting-grown plums on their own roots do well in New Zealand.
Pears are so large they are usually grafted onto quince to dwarf them, but since this is a different genus, there can be compatibility problems affecting the tree in later life. Often, an interstem of a compatible pear variety is used. Interestingly, seedling-grown pears live over 300 years, while pears grafted on quince seldom live longer than 40 years.
Apple rootstocks have been wellresearched for commercial purposes. East Malling Research Station, a horticulture and agriculture research institute in Kent, England, identified the properties of a range of apple rootstocks in the early 1900s, and M9 and MM106 are two commonly in use in New Zealand today. M9 is dwarfing – growing to about 30 per cent of normal height and MM106 is a heavy and early producer that grows to 70 per cent of full height.
The most obvious aspect of any rootstock is its effect on plant height.
Commercially, dwarfing rootstock is now preferred as it reduces pruning and picking costs. But a small tree also has a small root zone, which means it needs support against wind and is unable to source quantities of moisture and nutrients. This is fine for orchardists who grow their apples on wire frames and regularly water and fertilise, but for the easy-care home orchard, a vigorous tree will grow a large root base, anchoring itself and seeking out its own food and water.
Of all the fruit trees, apples are the easiest to graft. If you have a favourite apple tree you wish to replicate, select your scion wood now (in midwinter) and keep it refrigerated for grafting in spring. Robert and Robyn Guyton’s Open Orchard Project also sells a range of heritage scion wood
from Southland orchards.
The scion wood should be a year old.
It should be about pencil thickness with three to four good plump buds. Cut and store in a plastic bag with some damp paper towels or sphagnum moss to provide moisture – you don’t want it drying out. Label and seal the bag well and store it in the fridge. The fridge is perpetual winter for the scion wood.
Grafting new scion wood onto an existing tree is called reworking and provides a strong, established root base for the new growth. This technique was used extensively in kiwifruit orchards to quickly replace varieties attacked by PSA.
Check the Events page: Tree Crops Association and other local groups often host grafting workshops.
Bind the union tightly.
A two-year-old union still visible.