Propagating with Rootstocks by Allen Gilbert

As a general rule most fruiting plant species are graft compatible within their specific group so that apple on apple, pear on pear, plum on plum, peach on peach (includes nectarine), apricot on apricot, citrus on citrus etc. will generally graft successfully.  Plants (rootstocks) grown from seed are often virus free and so have a better performance rate than scion to scion grafts but they too may have problems such as being susceptible to a given pest or disease.  It was not until scientists could produce virus-free plants and use an electron microscope to identify viruses (Plant Research Institute Burnley, Victoria) that it was discovered most propagating material in Australia pre-1960's was full of virus and some of these viruses had a tremendous influence on incompatibility problems when grafting.  Using virus free material (buds) improved growth and cropping almost tenfold and grafting success was also improved enormously.

Peach and nectarines (actually a peach variation) have been used as a rootstock for most of the Prunus species including peach, nectarine, plum, apricot, prunes (a plum variation) and almond.  There are variations between varieties and within species of the success of bud or graft 'take' (success).  For instance, the union may have a dwarfing effect, there may be 'overgrowth' between the scion and stock (one or the other grows faster creating a different sized trunk or stem at the union).  Some graft unions can perform well for a short period then die, others are mildly incompatible and can last years before decline occurs.  Some unions grow a large callus and eventually 'choke' the graft area with excess callous growth.  Others are quite successful.

Using seedling plants you, of course, are using a different cultivar/variety every plant you choose because although seedlings can come fairly 'true to type' and look the same and may even produce almost identical looking fruits, there are genetic variations in every one just like there are variations between brothers and sisters in human family populations.  If the original seed source tree is very isolated from other fruit trees of the same family it may give very good seedling without too much variation and they might be OK as rootstock material but the only way to find this out is to trial the rootstock material.  As trees age they can pick up viruses (i.e., transferred by sucking insects) that can affect the purity of the rootstock material and diseases such as bacterial gummosis and silver leaf can get into the plant system.  These problems can affect the way the plant will accept a bud or graft and can lead to incompatibility (will not form a graft) between bud or scion and the rootstock.  If you have a good rootstock it would be best to propagate the material from cuttings to get identical plants.  Peach and nectarine rootstocks are very subject to waterlogging and do not tolerate wet soils for long periods.  Flooding and waterlogging often occur on and within some of the typical heavy clay to clay loam soils common in Australia.

On the positive side of this exercise you may be able to grow a multi fruiting tree with peach, nectarine, plum, sloe?, prune, almond (may need an inter-graft of a compatible species), apricot all on the one tree or you can have one tree with many different varieties on it if your rootstock is OK!!  Personally, if you want to choose a rootstock for Prunus species, I would buy a grafted plant, cut it to below the graft area and then by stooling the tree, grow your own rootstock.  Alternatively, obtain material (i.e., hardwood cuttings) from a roadside cherry plum as they usually perform better than peach or nectarine re compatibility and disease/waterlogging/climate/pest and disease resistance.

For your information, I have last spring (2010) cut down a very old cherry plum tree that had five limbs over 200mm wide, one metre about ground level, and into these I placed over thirty bark grafts of about 8 different cultivars of plum, peach and prune gathered from local home garden trees.  The inserted graft scions were sealed with grafting paint on the upright end and the scions were then enclosed in a moisturized plastic sleeve.  The success rate was great, only three grafts failed.

Sheryl:  One of our members Ray Johnson from Gin Gin does a lot of grafting and contacted Allen Gilbert and asked about grafting.  This article (above) was his reply.  Allen has written numerous books on various aspects of horticulture.