BBC Focus Magazine

[Esther]

I finally managed to log back in!

I have a little mystery for you all. Why do nettles catch fire in a microwave?



There's a thread on it here http://www.permies.com/t/13787/cooking-food-preservation-food-choices/Strange-nettle-reaction-Microwave#124137 but no real conclusions were ever drawn.

Ideas anyone?

[KingPhillip]

There's no mention in the linked thread whether the plate of nettles is resting on a turntable in the microwave oven. If the sparking and charring occur with the rotation, then the lensing would and should be ruled out.

My wildshot guess rests on the "capillary" system wherein the minerals serve a purpose bunched up near the joints where branches grow. Without the water, the carbohydrate fibers are susceptible as dry twigs would for a campfire.

[M Paul Lloyd]

Hello Esther, goodness me it's been a while. Hope all is well with you?

As to why Nettles, in particular, should combust quite so readily in a microwave............ I really don't think I can expand much on kingPhillips input to be honest.

Going by the photograph it appears that the microwave radiation has become concentrated in one particular place and caused it to overheat and carbonise, which suggests that the microwave in question was perhaps not equipped with a turntable? Or that the nettle in question had a significant metalic mineral contamination which could cause arcing in the way that foil or metal container might do.

Personally I have always prefered my nettles (sans the rather chewy stalks) lightly blanched in boiling water myself.

[Esther]

Well the photo was taken by someone who tried to replicate what happened to the person who originally asked why it did that. So it does seem as though it's repeatable. And they both seemed to burn in the same place - just below a leaf joint. I'm just very very short on nettles here so I can't experiment myself.

Glad to be back, by the way. Finally enjoying a bit of freedom after all that nursing duty!

[M Paul Lloyd]

"After all that nursing duty" .................. Right I think I get your drift. Oh well glad to have you back.

Interesting that it should be so localised but that would suggest a build up of minerals of some kind at that point?
Perhaps?
After all Nettles do tend to drag quite a lot of stuff out of the ground don't they?

I'll do a bit of digging and see what I can find out.

[M Paul Lloyd]

O......K.... Right well you know I think that this might actually be giving us an insight into the inner working of the Nettle that might not have been fully researched as I can't really find anything on this subject. That's not to say it isn't out there but for someone looking for a research project this would be worth a try.

As far as i can work out Nettles contain quite high levels of the metallic elements calcium, iron, magnesium and potassium and just as Peas tend to concentrate nitrates in their roots so I am inclined to think that Nettles do much the same sort of thing (as suggested by KingPhillip) which may explain the odd results when they are put in a microwave.

[Esther]

Nettles *are* supposed to be very high in iron, and they are considered to be 'dynamic accumulators', reaching deep down into the soil and bringing various minerals up into the rest of the plant. Maybe what I need to do is sacrifice one or two of my exceedingly limited supply to test, then find other plants that are considered to do similar things and experiment with them.

Hope my microwave survives the experience...

I originally thought it might be something to do with the silicon hypodermic needles they inject poison into you with when you pick them, but it doesn't seem to fit with where they burn.

[M Paul Lloyd]

Also silicon is a chemical element and although a tetravalent metalloid, it is less reactive than say carbon.
In the early days their was some confusion over silicon's properties and given its location on the periodic table was named silicium with the 'ium' part suggesting it was a metal, although this was later ammended when its true properties were better understood.

I would cheerfully conduct some experiments myself Esther but Nettles do not seem to thrive this far north, especially after a couple of really hard winters,

[Thinker]

More begs the question, why would you put them in the microwave in the first place?

[Shadowwolf]

I originally thought it might be something to do with the silicon hypodermic needles they inject poison into you with...

Thought similar meself but then thought that such would mean the leaves and elsewhere should also take a hit which they don't appear to have done.

Nettles *are* supposed to be very high in iron,

I'd be initially doubtful of iron content of the plant being responsible unless they somehow concentrate it as there are veg reputedly high in iron that can be microwaved without risk.

More begs the question, why would you put them in the microwave in the first place?

Apparently you can eat them, make soups from em and such, why I don't know but you can.

[Esther]

More begs the question, why would you put them in the microwave in the first place?

You never had nettle lasagna?? You don't know what you're missing. 'Course, they're best if you cook them in a cast iron frying pan, chopped, sauteed in olive oil with onion and stirred into rice or pasta.

And why eat nettles? 'Cos, assuming you have some growing nearby that haven't been peed on, they are free, very good for you, and very tasty so long as you cook them right.

Here's a link - check out the fifth video down for the lasagna recipe.

http://www.richsoil.com/nettles.jsp

[M Paul Lloyd]

Can't say as Nettle Lasagne appeals to me but I have eaten Nettles and enjoyed them... although I find hunger can be a great spice.