The Niab Plum Demonstration Centre (PDC) operated between 2015-2025. Here we summarise the key findings from the Rootstock/tree architecture demonstration.
This orchard was the first to be planted at the PDC in 2016, so yield data has been gathered since the first fruit was picked in 2017 and the latest results were shared with visitors at Fruit Focus. The orchard was planted with 10-tree plots of Victoria on four different rootstocks (Wavit, VVA1, St Julian A and Pixy) using four different tree architectures (Narrow A Frame, Narrow Table-Top, Super Spindle and Oblique Spindle).
The Narrow A Frame and Narrow Table-Top trained trees were planted at a density of 2,381 trees/ha, while the Spindle trees were planted at half the spacing, and so double the density at 4,762 trees/ha. Three of the rootstocks (Wavit, St Julian A and Pixy) were planted using all four training systems, but VVA1 was only planted on Super Spindle and Oblique Spindle training systems.
In addition, two single rows were planted on St Julian A rootstock using one row of Fan training and one row of Candelabra training. As the original orchard planting design was not fully replicated, yield data could not be analysed statistically.
The accumulated yield data had been gathered over seven seasons, although no fruit was picked in 2021 following complete flower loss as a result of 16 frost events in April 2021. Of particular note, the top three highest accumulated Class 1 yields per tree to date have been recorded on Wavit/Narrow A Frame (56 kg), St Julian A/Narrow Table-Top (51 kg) and Wavit/Narrow Table-Top (48 kg) systems, all at a tree density of 2,381 trees/ha.
However, as they are planted at twice the usual tree density, the highest accumulated marketable yields per hectare to date have been recorded on Spindle trained trees including VVA1/Oblique Spindle (38 kg/tree), Pixy/Super Spindle (31 kg/tree) and St Julian A/Oblique Spindle (28 kg/tree).
Of the two single rows of Victoria on St Julian A rootstock, the Fan system produced an even higher Class 1 yield per tree than any of the replicated plots (85 kg/tree) which equated to the fourth highest yield per hectare (1,587 trees/ha), while the Candelabra system produced 53 kg/tree at the same tree density.
The average fruit fresh weight was compared in the most recently picked season (2023) when all trees were fully mature, with fresh weight ranging from 40.3 g to 56.8 g per fruit. Victoria on the VVA1/Oblique Spindle recorded the highest fruit weight as well as the highest accumulated yield per hectare.
When interpreting this data, growers should be aware that it is not statistically robust and should also note that, despite producing high yields per hectare using the Spindle training system, a number of VVA1 rootstocks died either during establishment or in the early years, whilst all of the other rootstocks prospered. Growers should also weigh up the benefits of the high yielding Spindle system against the increased establishment costs incurred using double the density of trees, along with additional picking, pruning and maintenance costs. Insufficient funding was available to record and compare the pruning and tree management costs of each system.
Key findings
Pruning and Tree Management Irrigation Variety Trial
The Plum Best Practice Guide
The Guide brings together information on plum production into one place and develop from that information recommendations for best practice in the UK.