Last year we tried our first Kumeras and had a pretty solid failure, reasonable tops but manky little tubers. We decided that we would shift to the other - sunnier - end of the section this year and, reading that they preferred heat we put them into a tyre to build up the temperature. By late December they looked like this.By this week they had practically taken over the space with luxuriant, leafy tops and strong leaders running everywhere. So today I cut back the foliage and, expecting nothing, lifted the tyre. Not bad eh?
That's 5.8 kilos of very attractive, dry, clean Kumera for practically no effort on our parts. Next year expect 3 or 4 tyres doing the same. BTW, we grew them on top of the wood mulch to try and simulate the pan that Kay Baxter said we needed. Looks like that worked.

They also grew from tupu that came from a tuber we put into sand in about August 2009, took the seedlings for the failed crop from that and then just left the tuber in the sand in the greenhouse till about September 2010.

Seeing they had not died I carefully took them off the parent and planted into the tyre, bingo.

I've taken half a dozen growing tips from this crop and put them into cutting sand to see if we can use them for next year's crop. Stay tuned.

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Comment by Virgil Evetts on March 27, 2011 at 10:11am

My understanding about tyres is that over time they "probably" absorb a quantity of exhaust particulates that have ended up on the road, along with motor oil etc. As tyres become worn they became somewhat porous, at least on the outer surface. This theory seems plausible to me, but I’m not sure it would be a great enough risk to put me off using tires. Treated timber is far more worrying in the food garden.

Comment by Stillcookin on March 27, 2011 at 9:18am

If the black plastic does leach something into the spuds, it sure does taste good...with a little butter. :)

Comment by Earl Mardle on March 27, 2011 at 9:13am

Stillcookin. Fair point, its about informed consent I suppose and right now I'm leaning to the side of "at 60 I probably already have what's going to kill me I just don't know it yet" so we are talking margins here.


BTW, are you sure that the black plastic doesn't leach something into the spoil that gets into the spuds?


Comment by Stillcookin on March 26, 2011 at 10:48pm
The Kumera you grew there, I assume, is what we call a sweet potato? I have found that growing them in long, raised beds, with a soaker hose and covered in black plastic, works better than a tire. I think they just stay warmer. Heat is the key. I've grown regular potatoes in tires but found it too cumbersome. Finding enough dirt to keep them going higher and higher just wasn't worth the effort. As far as contamination, I don't really know for certain, but the article makes sense to me. I stopped using them 2 years ago, so if they were poisoning me, I'm hopefully not that close to death yet, and stopping has saved me! Use at your own risk I suppose.
Comment by Earl Mardle on March 26, 2011 at 8:39pm

Hi Stillcookin. I found that one as well, and I have a strong suspicion that he is right, but I'm not a materials scientist and, again, he makes an assertion without providing evidence so I used the other one which had the merit of at least offering some alternatives.

I think there is a case for some serious investigation of the question because tyres represent a very good way for people to grow their own food in small, controlled spaces. One day, when our governments wake up to the reality of the meaning of food security, maybe they will. My wife's nephew is a soil scientist and he is coming home from Aus later this year, maybe I can encourage him to apply for the necessary funding to do the science.

Comment by Stillcookin on March 26, 2011 at 12:55pm

There is no appreciable risk in using recycled tires in the vegetable garden. While it is a fact that rubber tires do contain minute amounts of certain heavy metals, the compounds are tightly bonded within the actual rubber compound and do not leach into the soil. One of the ingredients in the rubber recipe is zinc. Zinc, in fact, is an essential plant element. I also expect that rubber is safer to use than treated lumber that contains copper and arsenic. Tires are durable. The very qualities that make them an environmental headache make them perfect for our uses in the garden. Once they are in place, they won’t rot and will likely be there for your grandchildren to use.

Comment by Earl Mardle on March 26, 2011 at 10:09am


Good point. One that I have asked myself.

I have asked several people who assert the same to show me the proof that, in fact, toxins are leached from the tyres into the food that is grown in them. So far, nobody has been able to do that. Plenty of assertions that it "must" happen, but no actual evidence.

I did, however, come across this

On balance, until there is better evidence that there is a valid risk, I'll probably stick with the practice.
Comment by Matt Moir on March 26, 2011 at 9:39am
The Kumera look great good work however I am concernd. Are old tires the safest options? Old tires are full of toxins that are leached into the soil and plants absorb these toxins.  Even though this looks like a great way to recycle old tires I'm not sure it's the healthiest way to grow plants that we intend to eat.
Comment by Maree W on March 23, 2011 at 9:43pm

Well done.  I did the same last year with a golden kumara, got a good result.

Done the same this year with a purple and a golden kumara.  Just harvested the purple one, only about half your haul though.  I was a bit late getting it in though.  Might leave the golden one for a bit longer.  Tops are getting a bit rampant though!

Will keep you posted.  My fingers are crossed too.

Comment by Jane Maarie on March 9, 2011 at 4:54pm
Whoo hoo that's awesome Earl! You have just reminded me to go check on my kumara plot in my trial gardens too now.  Fingers crossed hehe.


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