Cherries catching up on dwarfing rootstock

Selections of Gisela® cherry dwarfing rootstocks have recently been licensed for the New Zealand orchard industry, and will become more widely available to growers from 2026.

Waimea Nurseries in Nelson confirmed that Gisela® 6 and Gisela® 12 are in production and Gisela® 5,13 and 17 are currently under importation and in quarantine, which is quite an advancement for the industry.

Gisela® 12 and 6 are currently being grown indoors in tissue culture at Waimea Nurseries’ laboratory and are being trialled on orchards in Central Otago – including Clyde Orchards and Suncrest Orchard in Cromwell.

Trials of dwarfing cherry rootstocks are underway in Hawke’s Bay as well.

Manager of variety development Tallulah Simpson says more of these will also be available in commercial numbers at the end of 2026.

When Professor Dugald Close of the University of Tasmania came to New Zealand back in July, he said Australasia still had a long way to go until benefits available in America and Europe, such as widespread availability of dwarfing rootstocks, were realised.

Dwarfing cherry rootstocks bring great opportunities to set up more intensive growing systems, but Waimea Nurseries says that up until now they have been difficult to propagate in a nursery environment.

“It’s not easy and we are cautious,” general manager sales and marketing Kate Marshall says.

The benefit of growing the rootstocks from tissue culture is that they are virus free.

Growing on dwarfing rootstock as opposed to traditional Colt rootstock means that growers can produce very large volumes quickly, Kate says.

Orchardists have been reluctant to use them in the past because they came at a cost, and the investment only paid off if their soils had enough nutrients, and they could successfully implement the new changes into their orchard systems.

Tallulah says New Zealand has been behind the United States, Europe and Chile on availability of these rootstocks due to difficulties with importing the plant material, and because they require a lot of investment.  

Gisela® has already been well commercialised overseas and Central Otago is ideal for using dwarfing rootstocks because it has such a unique climate and soil conditions, and a range of different soil types throughout the district as well, Kate explains.

But dwarfing rootstocks require full efforts from the growers to make them viable and many growers now realise this.

Clyde Orchards first planted a row of Gisela® cherry dwarfing rootstock back in 2018 as a trial, and their output is looking promising.

Manager Kris Robb says the issue was being able to make it worthwhile enough for the business, and to do that you need larger numbers of trees, (such as a whole block) to work with.

Bulk amounts of new rootstocks were necessary to enable growers to manage their orchard systems more efficiently, he said.

Kris says the lack of dwarfing cherry rootstocks has been detrimental to the overall productivity of the industry.

“It has probably done some underperforming varieties an injustice by not being able to source them on dwarfing rootstocks.”

Kordia, Regina and Folfar were three cherry varieties that sprang to mind, but he acknowledged the challenges were on the side of both the grower and the nurseries to make it work.

“It has taken a long time for people to learn, and for the nurseries to get their systems right.”

More orchards will now look to start using dwarfing rootstocks as they become available.

“If you can pick more fruit then your harvest costs reduce. You end up with smaller, more compact trees that are more efficient to prune and pick,” Kris explains.

Growers will see returns faster and their yield per hectare will be higher as well. 

With Colt rootstocks still making up 99 percent of the industry, the new dwarfing rootstocks will offer growers fruiting options in two years instead of the standard five.

Cromwell grower Michael Jones of Suncrest Orchard planted 10,000 trees over two different time periods, but says it is still early days to know how they will perform.

He received some of the Gisela® 5 and 12 in 2020 and planted more in 2022.

“We were given permission to graft and bud several varieties onto those stocks and grow trees for our pergola system at a density of 4,000 trees per hectare.

“Success rates varied from 40 to 70 percent depending on rootstock and variety. Usually, the failure resulted in the rootstock growing on and the bud or graft failing, so this enabled the rootstock to be re-grafted.”

The grafting and budding had been done onsite by contractors, and so far he has had a positive experience.

“We appreciate the input from several people with advice on what we could be doing or trying in this situation, and it was great to float ideas past people like Andy McGrath or Ronald Vermeulen and get their perspective on what we were doing.” 

Michael says because of the options nowadays with growing systems, it will be interesting to see how the industry progresses through the next decade.

“We have investigated the use of dwarf stocks because we are frustrated at inconsistent yield and the time it was taking for less intensive plantings to reach full yield; also because of the potential to maximise quality and size and reduce labour and other growing inputs.”

Admittedly the capital expenditure is a large cost, but his advice for growers is that they should be trying different stuff on their blocks, “whether it's two trees, two rows or two hectares. If you don’t try, then you don’t know. I am really looking forward to seeing and working with our new blocks as they start to go into their production phase.”

With dwarfing rootstocks growers can also plant more trees per hectare, which improves land use efficiency.

Over time, existing orchards will be able to redevelop into higher density orchards, which means less land use, but maintaining the same volumes on a smaller footprint.

Summerfruit NZ technical advisor Richard Mills says dwarfing stocks will also be a major benefit to other cherry growing areas, particularly in the strong Hawke’s Bay soils.

“The earlier potential harvest period should also benefit consumers due to a longer harvest season.”

He says good dwarfing apple rootstocks that emerged about 20 to 25 years ago were a significant factor in enabling that product group to make huge steps forward to increased yields on a smaller footprint.

Waimea Nurseries is currently propagating the new dwarfing cherry rootstock selections in an ‘Ellepot’ which has a paper membrane, and they are grown indoors in a ‘Cravo’ house (a glasshouse with an automatically retractable roof).

The baby plantlets come into the Nelson nursery for growing on, grafting, and then growing on some more until they are ready to supply to growers.

“We’re hoping that we have more success with these in a temperature-controlled environment, they are gentler on the plant than in a traditional field,” Kate says.

Growers have managed extraordinarily well with the vigour of Colt rootstock in New Zealand orchards, using FOPS (Future Orchard Planting Systems), UFO (Upright Fruiting Offshoots) and pergola growing systems, and techniques to improve productivity, due to the lack of dwarfing rootstocks, she says.

Tallulah notes that cherries from New Zealand are a premium export, and soon with more availability of dwarfing rootstocks will become more competitive in this space.

“Central Otago is an incredible growing area that produces top quality fruit, and we as a nursery want to give orchardists every opportunity to make the most of that."

 

This article was first published in the September 2024 issue of NZGrower & Orchardist.