Seen at The Festival of the Tree

...if you would be happy all your life, plant a garden ~ Chinese proverb

Friday, 7 September 2012

Red vs Green Lettuce: What Do Slugs and Snails Really Like?

Luckily this snail was exploring the possibilities of compost digestion before deciding to attack my lettuce 'Amaze'. ...Or was it?
As reported previously in August's Salad Days, we've been having an interesting #saladchat on Twitter recently about the seeming aversion slugs and snails have to red lettuces.

The majority of you reported this is so with the varieties you've been growing this year. This is a top tip, particularly for any wet year which leads to a population explosion of these pesky pests. Resistant varieties particularly mentioned were Red Salad Bowl and Dazzle.

Others said they hadn't noticed any difference, or indeed their slimy populations seemed to prefer red varieties such as Lollo Rosso, so it seems it's not quite as simple as red vs green. @littlesaladco said he'd found sappiness and leaf thickness was important, with the more sappy, thinner leaved varieties being preferred.

During this conversation, I vaguely remembered something I'd studied in A Level biology, where slugs  showed an aversion to plants producing compounds from the cyanide family (thankfully not enough to be poisonous to us!). I believe this is what Alys Fowler was referring to at a talk I went to earlier in the year when she mentioned lettuces produce bitter tasting compounds when nibbled. It's a defence mechanism which usually prevents further eating: probably not enough for a wet year like this one with slugs and snails in abundance though :/

Then came the breakthrough. Zoe Lynch came back with a reference showing the presence of anthocyanins in red lettuces might be a key factor. I'm also wondering if these levels are higher in sappier lettuces irrespective of their colour. Of course there may be other factors at play, all contributing to a sliding scale of nicer tasting  (probably sweeter) and juiciness, with mainly red at one end (not so palatable) and mainly green (oh so tempting) at the other.

Some saladchatterers said they found red lettuces weren't as nice as green ones, as they tend to be more bitter tasting. It looks like it's not just our pesky pests which have a preference for sweeter tasting, generally greener lettuce ;)

With thanks to Annemieke who originally posted the comment which led to our conversation on #saladchat. Also thanks to the people mentioned above plus @CarlLegge, @CountryGate, @karlasparlour, @maogden, @nicelittleplace, @PatientGarden, @Swanimages, and @wellywoman for joining in the conversation.

I feel the need for some field trials next year :)

NB I also found some other references around this subject if you're interested:

8 comments:

  1. Fascinating. Thanks ever so much for this. Perhaps the answer to bitterer leaves is a sweeter dressing.

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  2. Slugs prefer the green lettuce in my garden - the red, thankfully, they have left alone so far this year..

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  3. Slugs and snails might have a preference but rabbits certainly don't care, anything goes! I wonder if its the same with green and red cabbages?

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  4. Now this I have to test. I have seedlings of both salad bowl red and salad bowl green, perhaps I'll plant them side by side in a known snail area and monitor the results - of course I may end up very sad and with no lettuce but at least I'd be wiser for it I guess.

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  5. It seems completely random in my garden. They demolished the spinach, ate most of the rocket but ignored a whole row of green lettuces. The lettuces were quite boring and didn't have much flavour anyway. Perhaps slugs do have some good taste then!

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  6. Oooh, that is interesting. I wonder if this carries through to oriental leaves. Weirdly, my red Pak Choi seems to be being nibbled more than the golden form, which is also growing away more strongly. You almost tempt me back to twitter - get the behind me! It took over my life, I have no willpower...

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  7. The slugs in my garden are generally not discerning at all, but I have also noticed that they tend to leave the red varieties alone, or at least only eat them if there is nothing else around. But it's probably correct that they like the bitter ones less, I have a green one, can't remember the name right now, but it's slightly bitter and I never see any slugs on it. They might happily hide under it, but they don't nibble. Or devour.

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  8. Helen - that's a good idea. I also need to do some further research on the cause - a book I'm reading at the moment mentions a couple of compounds associated with bitter taste. I need to find out whether they're the specific names for the more general ones I've referred to in this post.

    Dani - welcome! Another vote for the red ones.

    Andrea - yes the topic of rabbits (and deer!) changes things massively. Luckily I have neither to deal with. @Carllegge also speculated the same re cabbages. I can't say because I've only grown red ones! What's your experience?

    Liz - that's exactly what I'm hoping to do next year. Perhaps we could compare notes next year :)

    Claire - welcome :) It seems your slugs prefer stronger, more peppery tasting leaves!

    Janet - they're certainly trying to have a go at the oriental leaves I've just sown. But then, the Amaze lettuces next to them have now transformed into a totally red lettuce since I took the photo. If you do get back on twitter, my chatty id is @malvernmeet and I'm always happy to have a #saladchat :)

    Helle - let me know if you remember the name of your resistant green lettuce, it would be great to add it to the trial

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