Oak Valley

Doubling up

Dual leaders complicate tree transport, storage, planting and management. Krige considers them a means to an end rather than an ideal solution.

He made it very clear that they opted for dual-leader trees so that they could plant Granny Smith on G.778 under nets – not to save money. He also advised against trying to make dual leaders on the farm. Growers should order their dual-leader trees well in advance.

The leaders should form a V at their base rather than a U. A U-shaped base encourages vigour on the inside of the
U. Krige cautioned against spacing dual-leader trees 2 m apart, as this will either result in a U-shaped base or a large unproductive area at the bottom of the tree.

Toothpicks were used to improve the crotch angles – this is standard practice at Oak Valley. Krige would have preferred to use elastics to train branches much earlier in the growing season, but their elastic order was delayed by the global shipping crisis.

Unequal leaders can be a problem depending on how the trees were made. The Oak Valley trees were made by grafting a single bud onto the rootstock and then later tipping the scion to allow two lateral buds to sprout. Their leaders are close to the same size.

Krige explained that unequal leaders can be managed with all the usual tools – pruning, girdling, fruiting, and plant growth regulators – to even out the difference.

Making breaks

Excellent nursery trees with adequate chilling from cold storage gave the orchard a great start, but the establishment was literally bogged down due to heavy rains in the third quarter of 2021. Krige related how planting was done in stages as weather allowed.

By the time the last trees went into the ground, the first ones had already begun growing – so no rest-breaking agents were applied. In hindsight, he considers this a mistake.

Not applying a rest-breaking treatment exacerbated the natural tendency of Granny Smith to form blind wood. Krige plans a full assault on blind wood and leader breaks in the coming season. The trees have already been notched and this will be repeated as necessary.

Krige is aiming for a narrow canopy with relatively weak branches up to the full 3.5 m height of the trees. He plans to use renewal pruning on the leaders and will stub about 20% of the branches annually. Krige thinks that renewal on the branches will be too labour-intensive at a density of 3 571 leaders/ha.

One challenge with pruning these trees is that Krige wants to avoid stimulating vigour – which is exactly what pruning does. Putting a crop on the trees this season will also help to check unwanted growth.

Safety nets

Growers in hail-prone regions have long recognised the value of protective nets. A more recent development has been their deployment to reduce sunburn. Granny Smith apples must be green to fetch good prices and nets help to achieve good green colour while preventing sunburn.

The orchard is covered by a grey net that has a 14% shading factor. Krige shared a previous Oak Valley experience of planting Granny Smith under a white net that provided insufficient protection while the canopy was still filling out.

Traditionally, Elgin is not a hail area, and the nets can be retracted for much of the year. Krige likes to have the trees uncovered until about the end of November for three reasons. The first is that green colour in Granny Smith is determined by light exposure in the six weeks following fruit set. The second is that Krige wants to minimise the impact on bees during the pollination period. And the third is that flower induction for the following season occurs early in the current season and is improved by light exposure.

Krige retracts the nets again as soon as possible after harvest to give the trees maximum light for the remainder of the growing season and as much chill as possible during winter.

Cover crops

Medicks were sown by hand in the tree rows in early autumn, using a perforated bottle. Six weeks later the plants were growing strongly but the medicks in the end rows fell victim to those ever-annoying weevils.

Weed control was not necessary before sowing because the trees were mulched with wood chips at planting and the mulch suppressed weeds. Krige considers mulching an essential step in orchard establishment.

Oak Valley has had cover crops in other orchards for several years. They have found that the medicks become self-sustaining if successfully sowed for two years running. Medick seed needs scarification to germinate and a single round of sowing yields poor germination the year after.

The medicks die down naturally at the end of winter but can be scorched if necessary. The dead cover crop traps leaves and other organic matter to form mulch for summer.

Interventions such as cover crops and protective nets are moving into the mainstream, and helping growers complete the puzzle of a profitable orchard. Krige emphasised that growers should see these as tools to support the execution of the fundamentals – apple farming remains all about intercepting and distributing light.

Acknowledgements

Thanks to manager Neville van Buuren for hosting the visit and technical adviser Graeme Krige for leading the discussion.

Featured Image: Dual-leader Granny Smith on G.778 at Oak Valley