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Frank takes dynamic approach to pruning
Frank takes dynamic approach to pruning

Te Puna avocado grower Frank Baggenstos has been experimenting with methods to bring the best out of his avocado trees for the past 20 years or so, and he says he’s still learning.

He has long been recognised as an innovator in the industry, having started annual pruning long before it became the norm. Such was his commitment to the advancement of avocado production, he was often asked to host field days at his orchard so others could see his efforts.

But techniques and the science have moved on, says Frank, and in some cases he no longer agrees with the advice he gave out in the 1990s. These days, Frank prefers to concentrate solely on his experimentation; saving his comments until he can demonstrate success.

“A lot of what we do with avocado trees is all theory,” says Frank. “I want to prove that over three years I can produce a consistent crop from a very biennial orchard.”

The first thing you notice in Frank’s orchard is the light – no tall, shadowy trees here. He likes to keep the underside of the trees wide open, partly for access and partly so sunlight can reach the fruiting wood, topping them at 4 metres without destroying the canopy.

Many of the trees have two heavy espalier-style branches – often propped up because of bad sunburn and frost damage caused by the timing of major prunes. The props enable limbs to support the extra weight of a big set without breaking. Frank prunes to achieve this shape in older trees, but trains his new plantings to grow along these lines.

“I have handled all the development work on the orchard personally, doing everything with my own hands, so I have come to know a little about growing avocados in New Zealand conditions.

“I am fanatical about pruning. A lot of it has been trial and error – mostly error – but in the process I have noticed some interesting things.”

Frank and Coryl’s 2.2ha avocado orchard is on north-sloping land near Te Puna (Tauranga) that dips down to sea level, exposing his trees to some heavy frosts. He feels if he can make it work year after year on this site his methods could open up other marginal land to avocado growing, and perhaps stretch the growing region into the Nelson area.

“Direct sunlight is very important,” adds Frank. “I use the flat topping method when pruning but lower my trees on the Northern end of the flat top, thereby tilting the top towards the sun. This allows more direct sunlight into the tree, and the suckers [shoots] grow more efficiently.”

Frank says suckers compete with each other and existing foliage for sunlight in order to become fruiting wood. He has seen suckers grow 2m in a year to reach the sun. Because his pruning method creates a lot of openness in his trees, he says there is reduced competition, enabling his suckers to grow to a similar non-shaded height and become fruiting wood much sooner.

Frank prunes to keep his trees around 4m high and also to enable easy hydralada access into the trees, making sure there are no cross-over branches. “After doing this work, I think more intensive growing is possible, perhaps 5m by 5m.

He is also following his instincts in his battle against phytophthora, which he believes is caused by wet, compacted un-aerated soil. He believes that the humping and hollowing and ripping of the ground for new plantings that some growers are doing is great.

“For the past five years I’ve been mechanically decompacting the ground around my existing trees. It’s hard work, and I’m now looking at using a Bobcat with a grapple. Orchardists tend to mow right up to the trees so machinery has been compacting the soil over the years. Decompacting allows the roots to flush.”

After breaking up the soil Frank applies gypsum powder, allowing the rain to drive the gypsum into the cracks. He says this is “100% better” than simply spreading the gypsum on top of the ground as most of it will not penetrate compacted soil.

“The roots love such aerated conditions. My trees recovered dramatically [from phytophthora] and I have not needed to treat them again. My trials are ongoing.”

Frank is a full-time builder and part-time orchardist. He says the avocados are his stress relief – a sideline that enables him to switch off from the demands of building.

“Growing avocados is a challenge in New Zealand and it is this challenge that makes it interesting for me. Some orchards on good sloping, frost-free sites will just about grow avocados automatically, but such sites are rare.”

Frank has just installed a frost-protection system that relies on sprinklers to form ice on the leaves as a shield against frost. “I believe this system will help me combat biennial bearing. I’ve been trialling various methods to grow avocados for about 20 years and I’m still passionate about growing avocados. I applaud the work AIC and other independent growers are doing exploring other methods.”

He is also pleased that the two biggest grower groups have got together as AVOCO, rather than scrapping with each other for market sales.

“This will also encourage our experts and growers from both camps to share information and ideas, and that can only be good for the industry and all growers.”

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Partners: Southern Produce, Primor, Team Avocado