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PRI New Zealand (Koanga Institute)
PRI New Zealand (Koanga Institute)
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NZ Heritage Potato Report

Project: PRI New Zealand (Koanga Institute)

At the Koanga Institute, we're working to improve the health of our collection of NZ heritage potatoes.

NZ Heritage Potatoes in Danger!


Over the past 20 years it has become increasingly apparent that our heritage potatoes are deteriorating (far smaller crops from each potato planted with far more evidence of disease and pest issues), and since the introduction of the psyllid, (which brings a host of damaging viruses) the problem has dramatically worsened.

In the 2011 harvest season we harvested marbles 1-2cm diameter. We were unable to eat anything or sell the seed at this point. This was our national potato collection so it was a very serious situation.

On top of the pest and disease issue, or part of the reason for these issues, is the fact that our New Zealand soils are also now seriously de mineralised. Just as we humans can not maintain our health or the integrity of our DNA over generations if we do not feed our body well, the potatoes are not able to maintain the genetic strength they began with if we do not feed them the minerals from the rich soils they evolved with.

It is many years since serious selection work has been done by home gardeners maintaining these lines, although in recent times there are several groups beginning that process again including Joseph Land’s work in the Hokianga where he grows a range of the Koanga Institute seed potatoes. Until now the Koanga Institute has not been in a position to improve our entire collection, our resources have simply been overstretched.

Other people and organisations in NZ who hold serious potato collections (including industry growers) are endeavouring to get their collections cleaned up by ‘tissue culture’ in the lab, which is a way of taking the viruses out of the potatoes and beginning again with virus free seed potatoes. This is a costly process for each variety, and we do not believe this will strengthen the genetics of the potatoes. We have seen a kumara collection lost in this way, and the tissue cultured plants are vulnerable to all the viruses and psyllids that continue to exist in the environment, when they are planted again in the real world.

Here at the Koanga Institute, we believe that we must find an alternative solution, one that can be followed by home gardeners in New Zealand to strengthen and maintain the integrity of the plant's DNA. The science of epigenetics has taught us that


In this instance, this means that if we are able to supply all the required nutrients to the plants, and create a strong and healthy soil (environment) full of beneficial microbiology and minerals, then the strongest plants will adapt and survive, and we can select from these to maintain the lines

The fertiliser program is as follows:

  1. Soak potatoes in compost tea for 12 hours then place in a bag with Koanga:Seedling Inoculant and shake to lightly cover potatoes with inoculant.

  2. Prepare your potato trenches and apply to each meter of trench: 400g of EF:Nature’s Garden (fertiliser mix containing a wide range of nutrients balanced according to the principles of Dr Carey Reams) 200g of EF:Active Calcium (lime that has been composted with a carbon source to hold the calcium in the root zone), 200g of biochar

  3. Plant potatoes, cover them, then water with liquid biochar

  4. Spray fortnightly once they emerge with compost tea and on the in between weeks with EF:VegeFoliar three times, then change to EF:Fruit Foliar

  5. Last 3 foliar sprays before harvest, add EF:Manganese chelate which will strengthen the quality of the seed. Manganese is the element of life that gives seeds their strength!

We planted a trial plot of 200sq m, which means that we were able to plant approximately 20 plants of each cultivar in our collection.

With the help of a 1935 NZ Department of Agriculture Potato Growers booklet (1942!) we kept a careful eye on each potato plant as they emerged and rogued (removed) almost all (couldn’t bear to remove everything, that would mean losing a line!) plants that appeared with crinkly leaves and or yellow blotches on the leaves. We also removed all plants that looked spindly and weak, compared to others. Some cultivars were noticeably weaker than others and we decided not to remove all plants where an entire line looked weak. We rogued the entire patch three times in the first three months of growth, finally just before flowers opened.

Once the flowers were open there was a marked increase in insect activity, with the insects potentially become disease vectors... so the aim of the rogueing is to remove all diseased plants before the insects come in and spread the disease.

We used a BioPesticide (entirely composed of beneficial microbes and fungi) to keep psyllids to a minimum and are very excited about the potential of this new product.

We also received information from Scott Lawson showing that a trial in the USA showed that erecting a black shade cloth fence around the potato patch works to keep out over 90% of psyllids as well.

We used our refractometer to test regularly before and after spraying to make sure we were actually doing what the plants needed, and we raised the brix of the potatoes to around 14 which is relatively high for potatoes.

At harvest we dug each plant separately, and weighed the tubers from each plant.

We selected our mother seed from the best tubers from the best producing plants from each cultivar, from the plants left after the rogueing.

We also photographed each variety for the website so you can all see what we have!

If you go onto our website you can see the individual results with comments and photos of each cultivar. Koanga Potato report

The Results

There were huge variations in the weights harvested from potatoes within cultivars. Some plants produced crops of over 3kg but with others only producing 0.1kg so the averages were very low this year compared to the harvests I was achieving 20 years ago.

Overall we were very happy to see our potatoes produce good size edible tubers that we were able to save beautiful seed from. We didn’t eat them this year, but will do extensive taste tests next season.

Selecting our seed from the healthiest, heaviest producers should increase the weight of crops significantly over 3 years or so. (In Joseph Lands experience 3 years is the time it takes to increase production and vastly improve a line)

Our goal is to achieve production of high quality, good size potatoes, heavy crops of around 3-5kg per seed potato planted, and be able to provide seed from these potatoes to our members and the general public. We are one year into this project now!

Healthy Vigorous growth


Key Successes and Understanding Gained from the Trial

  1. We went from diseased marbles to crops of healthy looking potatoes that we were able to save good seed from.

  2. The fertiliser program definitely felt like a huge part of the creating this progress, we certainly watched the brix levels go up, as we fed the plants.

  3. The tough rogueing of diseased plants is a key part of cultivar improvement, and was very hard to do when we were dealing with such small numbers of endangered potato.

  4. Selection of the best potatoes (biggest potatoes from the heaviest producing plants) is a key part of cultivar improvement.

  5. Planting early ( before mid September, but preferably in late July or August) is key to avoiding psyllid as much as possible.

  6. Using either a 80cm black shade cloth fence around potatoes or Koanga Bio Pesticide or both will help keep psyllid numbers very low, other options could include using a special diatomaceous earth spray Koanga Psyllid Solution, and also Neem oil.

  7. Karoro, Whataroa, Urenika and Kowiniwini have been or standard best choices for a few years now out of this collection as well as Pink and Yellow Fir, but we were very excited to see a few more very promising lines showing up. I was especially excited by Whanaako, Stewart Island, and Wai –iti, and also Catriona.

  8. We understand based on the principles of epigenetics that the nutritional program we used, and the selection we did this past season will mean next years results will also be affected in a positive way by that. As we continue with the program the effects should compound and produce healthier and healthier plants and larger crops.

A piece of the puzzle from Bill Mollison

Finally, Bill Mollison told a group of us a story whilst at the permaculture Convergence in Jordan last Spring about potatoes, and I like it. We’ve saved all our aerial seed this season from our trial patch potatoes so we can incorporate his observations into our management and growing of potatoes next season

On his visits to Peru to learn about potato production and potatoes in general (Bill is a potato fanatic, years ago when he stayed with us I realised the extent of his love affair with potatoes when I saw what he actually eats – mainly meat and potatoes – but he is also partial to eel), Bill noticed that when the farmers go up the mountains to take care of their potatoes, they not only take care of those they have planted, they also take special notice of the wild ones that grow all around their gardens. When they see particularly healthy looking wild potato plants, they mark them, and harvest those later when they are ready. They then choose the healthiest wild plants that had the best crops of potatoes, and keep some of those each year to plant in with their cultivated potatoes the following year.

The idea is that when the seedlings flower the following year they will be flowering at the same time as all those in the cultivated field ad they will spread their strength and vigour to the cultivated plants via the pollen that is carried by the insects that love to visit the flowers. Apparently the constant cross fertilisation of the wild strong plants and the cultivated plants helps keep the cultivated plants vigorous, strong and healthy!!

If you would like to support this research work, please consider sponsoring a spud! Visit the koanga website for more details. Potato Sponsorship Program



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