Wednesday, 25 June 2014

Duck potato or arrowhead

I became interested in aquatic vegetables when watering plants in the morning and afternoon over summer was not enough.  The soil gets so dry here that no amount of water seems to be enough.

Planting in pots and sitting the pot in water works, but growing in the soil is difficult as the water gets sucked away from the plants into the subsoil.  Deep rooted plants such as comfrey are meant to be drought proof but they do poorly here as most of the soil moisture is in the upper layers of the soil and deep down is very dry. That is kind of the opposite of how things should be, but the climate here is semi-arid so all the rules are different.

Aquaponics sounds like a good idea, my small scale proof of concept tanks both work rather well, but the set up costs for a proper system are prohibitive.  Growing things in a bucket of soil covered in water sounded like a feasible idea so I decided to try some aquatic vegetables.  I have tried a few water vegetables and they have all worked well.

One of the best things about duck potatoes is that they look amazing.  They have cool leaves with arrow shapes.  People grow them on the edges of ponds purely for ornamental purposes.  I wish I had taken pictures of the leaves.  Next year hopefully I will remember to take more pictures while they are growing.

Duck potatoes in Australia
Duck potato tuber straight out of the mud, they are good looking little guys

How I heard of duck potatoes

I first heard of something similar to these when I was in the Arctic.  I stayed in a small village and the elders spoke of a water vegetable they traditionally used to eat but the young people have all but forgotten about, the english name was "Eskimo potato".  They said it grew in the mud under the water in a certain place, they described it to me and I did my best to understand.  As they did not speak much english and I did not understand much Inuktitut we did our best.

The next day I went out to the spot that was described to me.  It was a spot that was reputedly good fishing but some people said to never go to as large bears live there and they would kill and eat me.  I had a few close calls with angry bears earlier so knew they were not telling tall tales.  I went out and was followed by one of the town dogs who decided to follow me and protect me, he had protected me from a bear before so I figured I would be safe enough.  When I got there I saw lots of bear prints and bear poo, some of the bear prints were huge so I knew that large bears were around.  I wore board shorts and waded into the frigid arctic water and started to dig in the mud for something which I hoped was the word for 'tuber' and not the word for 'musk rat' or anything else that would bite me.  After a short time I found what I hoped was the correct thing, it looked a bit small but it is the arctic after all, then I found hundreds more.  I dug them up and threw them to shore.  I had planned on getting more but was too cold so took what I had back to the village and dried off and got dressed.

I was told never to eat these raw and did not know how to cook them so I did not try any of them, instead I divided them up and distributed them to several houses of the elders.  I figured if I did this without telling anyone the next time I saw an elder they would smile at me, something they only did rarely with me and never to any other outsider that I had seen.  The next day I was given some baked tubers, they were delicious.  I collected these tubers several times, most times the dog followed me and made me feel safe.  Each time I divided them between the elders and occasionally they gave me some cooked ones in return.

I have been searching for these "Eskimo Potatoes' in Australia but can not find them, the nearest thing I can find are these duck potato. If eskimo potatoes exist in Australia I would love to grow them and eat them.
Perennial duck potatoes
Duck potatoes growing in a bucket

How I grow duck potatoes or arrowhead in a bucket

I grew these duck potatoes in a similar way to water chestnuts.  I planted each duck potato at the beginning of spring about 5cm deep in a punnet of moist soil, it was no damper than any seed raising soil.  The plants then sprouted nicely.  When the plants grew a leaf I put the punnets in a container with some water, kind of like how you grow carnivorous plants.  The water level was kept below the tubers at this stage to prevent them from rotting.  When the plants were 10cm or more tall and the roots were coming out of the bottom of the punnet I planted each of them into a separate bucket where it would spend the season. 

The bucket had manure, clay and subsoil mixed into it and had been filled to 5cm from the rim.  This bucket had been filled with water for a few weeks so the nitrogen cycle could work its magic as fresh manure would burn and kill plants.  I had duckweed growing over the surface of the water.  From here I pretty much just kept the buckets topped up with water.

The little duck potatoes grew very well at the start, each getting several new leaves and looking great.  We had a few late frosts, the duck potato is meant to be ok with this but mine fared worse than the water chestnuts and had all of their leaves burned off, but they grew back.  They grew well until the heat of summer hit, so I moved the buckets into the shade of a tree and they picked up.  I let them grow there in the shade until winter came, doing nothing other than topping up the water when I was out watering the other vegetables.  It really was rather simple, there are no weed issues as the weeds can not survive being submerged all the time.

Duck potatoes growing in a 10L bucket with duckweed starting to cover the surface

The yield

Harvesting duck potatoes is simple.  The plants are allowed to grow Spring, Summer and Autumn, when the leaves die off they are ready to be harvested.  Growing in soft mud makes it simple enough to feel around and pull them out by hand.

The yield when grown in a pond or a bathtub is meant to be rather high.  I do not have a pond and wanted to know if I could grow them in a 10L bucket like I did with the water chestnuts.  I planted one tuber per bucket and the first bucket returned 17 tubers, most of which were edible sized.  There may well have been a few more large tubers in there too but my hands got too cold searching through the mud for them and the kids were bugging me so I stopped.  I could have tipped the bucket out and searched through which would have made things easier but I was trying not to lose all of the duckweed.  The other buckets yield should be about the same, if not I will try to write a comment or blog post about it.
Duck potato tuber yield
Yield from one 10L bucket, there may have been more but my hands got too cold looking for them
Using a larger container would have provided a larger yield.  Having the water deeper would have also been better for them too.  I think ideally the water needs to be 15 to 30 cm deep as the leaves get kind of tall and use the water to help support their weight.  They are a beautiful looking plant, one that could easily be grown in an ornamental pond.

Where to buy duck potatoes or arrowhead in Australia

I plan to grow these again.  Being perennial all I have to do is keep a few tubers each year to keep my little population going.  Next time I may try to find a larger bucket to see if that helps increase yield as much as I think it will.  I may also try to put a few fish into the water and see how they go.  I do sometimes sell duck potato tubers on my for sale page.


  1. I think of this plant as having great potential for improvement through active breeding work.

  2. Darren I agree completely. There are a lot of vegetables out there that have great potential for improvement and this is surely one of them.

    I wish more people did a little breeding (or even deliberate selection of desirable traits) with vegetables rather than just accepting things as they are. There are a lot of semi-domesticated plants such as this which have never had any real selective pressure put on them. As a result they often have a lot of diversity in their genes and vast improvements can be made in a relatively short time.

    I have read about someone who did a little breeding of this plant overseas and their results from a very short time sounded fantastic.

    I would love to do something like that but the one I have does not flower, or if it does flower it is certainly reluctant to do so in my climate. Being non-flowering stops it from posing a weed threat, but it also stops me from breeding something great.

    If I ever get my hands on a flowering form I will see what I can do. Failing that I may be lucky one year and have conditions just right so that these flower and set viable seed. I have had a few perennial alliums flower and set viable seed lately so I wont rule out anything.