Some species of fruit are commonly grown on their own roots: new plants are propagated by rooting, layering, or modern tissue-culture techniques. In some situations, special rootstocks may not confer any advantage or may be unavailable to the grower. Fig, filbert, olive, pomegranate, gooseberry, bramble, and other fruits are commonly grown without any special rootstock.
Though vegetative propagation of apple, pear, stone fruits, and many other species is a nearly universal practice, it does have some detractors. Here is an account of one advocate of own-root fruit trees.
Own-root apples in a Permaculture design
Permaculture designer and fruit nurseryman Phil Corbett has for a number of years been working on an innovative project involving growing fruit trees on their own roots. His work is based on research carried out by Hugh Ermen of the Brogdale Horticultural Research Station, home of the National Apple Collection. Corbett writes; "Hugh discovered that there are several advantages in growing apples on their own roots- that is, not grafted onto a rootstock. The graft union, which is a union between two genetically different individuals, always creates a degree of incompatibility. Not having this incompatibility, own root trees were found to have better health and better fruit quality. The only disadvantage of own root trees is that most varieties are more vigorous than is usually wanted. This means that trees may make a lot of wood at the expense of fruit bud production, giving big trees that take a long time to come into crop. Conventionally this vigour is controlled by grafting onto a dwarfing rootstock. With trees on their own roots, however, a number of traditional techniques can induce early cropping. Once cropping begins, the tree's energies are channelled into fruit production and growth slows down to a controllable level. The techniques that are usually sufficient to bring about cropping are:
- Withholding nitrogen, which would stimulate growth, and withholding irrigation, except in serious drought;
- Tying down one and two year old branches to the horizontal. This induces fruit bud formation;
- Prune in summer to stimulate fruit buds to form, and avoid winter pruning which stimulates regrowth.
Once cropping has begun, a normal feeding and watering regime can begin. The average cropping own-root tree can be maintained at a size very similar to the same variety on MM106 rootstock" (Phil Corbett, from The Common Ground Book Of Orchards, pub Common Ground, 2000).
He is also conducting research into the 'coppice-ability' of own-root fruit trees, including an experimental 'Coppice Orchard' project, wherein own-root trees are planted in north-south rows; "When the canopy of the orchard closes, a north-south row will be coppiced and the land in the row used for light demanding crops while the trees regrow. The trees on either side of the glade will have higher light levels on their sides and produce more fruit buds". Over time a series of parallel sheltered glades will be created which will be coppiced on a rotational basis, allowing for multifunctional use of land in order to produce not only fruit but also small wood products, soft fruit, vegetables and even possibly cereals, fungi and the more traditional bees and poultry. This is a project with much promising potential, and deserving of attention from the wider organic growing movement for the valuable lessons that will no doubt be provided over time.