Self-rooted trees cut costs
In an experiment, self-rooted pear trees were as productive as trees on rootstocks and cost much less.
This is not a story out of a horticultural book of fables. It is a story to ruffle your imagination.
While the search goes on unabated for the elusive size-controlling precocious pear rootstock, an experiment at the Tatura Research Institute in Victoria, Australia, has shown that pear trees propagated on their own roots can match the productivity of trees on a rootstock.
The cost of trees represents a large proportion (often more than 50 percent) of the total cost of establishing a Tatura Trellis planting. The experiment showed that pear trees can be propagated cheaply from softwood cuttings and made productive at an early age. The aim was to substantially reduce the cost of trees and so increase interest in the Tatura system of growing pears.
Leafy (softwood) cuttings of Packham’s Triumph taken in December (midsummer), treated with a root-promoting hormone, and then placed under a mist propagation unit, produced roots within 60 days.
The cuttings were then potted up, and in August (early spring), they were planted on Tatura Trellis as dormant rooted cuttings 1 meter (3 feet) apart in the rows with 4.5 meters (15 feet) between rows, for a total of 2,222 trees per hectare (968 trees per acre).
Each tree developed a leader to the left and to the right at 30 degrees to vertical (60 degrees in the V). Branches were trained to the wires with small plastic ties. Initial training and pruning were done in spring and summer. A dormant rooted cutting of Winter Nelis was planted as pollinizer at each trellis frame (15 meters, or 50 feet, apart). Trees were irrigated with microjets.
Adjacent to the Packham’s experiment was the first Tatura Trellis with Bartlett on Pyrus calleryana D.6 seedling rootstock planted at the same tree and row spacing.
Packham’s were grown for the fresh market and Bartletts for the cannery. Packham yields were compared with those of Bartletts for ten years (see Table 1).
The cost of raising a self-rooted tree was estimated to be less than one-eighth the cost of raising a tree with a rootstock.
Australian export standards were followed when fruit quality and fruit size of Packham’s were assessed. An average assessment for the last six years is as follows: unblemished fruit fit for export, 67 percent (ranged from 59 to 79%); limb rub, 8 percent; sunburn, 4 percent; misshapes, 8 percent; russet, 6 percent; and undersized fruit less than 57 mm (2.25 inches) in diameter, 7 percent.
Bartlett yields are shown as canning grade (larger than 57 mm diameter).
Well-managed productive orchards of Packham’s on Tatura Trellis in Australia (on P. calleryana D.6) and South Africa (on BP.1 and BP.3) produced between 72 and 81 tons per hectare annually.
Yields in Table 1 are equal to or better than those obtained from overseas reports of yields of different pear varieties on Old Home by Farmingdale and quince rootstocks at approximately the same tree density.
Propagating pear trees on their own roots has not been adopted by nurseries in Australia. Perhaps it was too radical. Perhaps the logic and persuasion were not convincing enough for a traditional nursery industry dealing with fruit trees.
With the ever-increasing cost of nursery trees, and a continuous emphasis on high-density planting, this experiment with self-rooted pear trees has shown that thinking outside the box can have boundless possibilities.Van den Ende is a tree fruit consultant in Australia’s Goulburn Valley.