Oi, Botanists, Answer This...

[Captain Spod]

What is the evolutionary advantage to herbs in having leaves and stems that taste nice?
Just wondering while I place my rosemary sprigs on my sausage and potato bake.
Thanks,
CS
Rosemary Sprigs? Didn't she use to be in Crossroads?

[jim360]

It can depend a bit on the plant, but at least half of the answer is that earlier on in the plant's existence, humans discovered that it tasted fairly nice and then started a programme of selective breeding, choosing only the tastiest plants to carry on for the next generation. So the advantage is often to us, and not the plant (or animal, as a similar procedure accounts for cows, sheep, pigs etc, that these days can sometimes be little more than living meat/ milk factories).

The other half of the answer is that the taste itself may sometimes be an incidental result of something that is beneficial to the plant -- in the same sort of way that eggs are tasty because they are just packed full of nutrition for a growing chick embryo. Alternatively, the taste can come from a chemical that is poisonous to certain animals that were natural predators, but is in too small doses to be a threat to us.

I suppose the short answer, then, is that the taste isn't important to the plant, but what causes it might be.

[rowanwitch]

Aromatic oils that evaporate in the air can be carried a long distance in warm climates. This is especially true of herbs like rosemary and thyme this means they are able to attract insect pollinators to their flowers more effectively.

[pixie373]

Interesting jim. Reading the OP made me question whether plants actually do evolve.

[rowanwitch]

Yes they do, including developing sub species in isolation just like animals

[Graham-W]

Alternatively, a nice tasting plant is more likely to be eaten and it's seeds spread more widely in the undigested bit of the fertilizer created.

[Peaspeculiars]

In my garden, the stronger tasting the herb, the less likely it is to be eaten by slugs. Rosemary, sage and thyme thrives, whereas parsley & coriander get slug-munched. So perhaps an evolutionary defence is the taste?

[rowanwitch]

Also rosemary Thyme and sage are tough slugs like juicy soft leafy greens

[pixie373]

Thanks rowan- just hadn't really considered whether they did or not.

[Peter Pedant]

evening capn

read a book on Bot -you will find it v v interesting ( altho I prefer zoo. myself)

Plants ( if they are not triffids ) are immobile as I am sure you have noticed...and so the question arises about the function of aromatic oils.
Honestly there will be a fascinating chapter on this....
attraction of insects ( pollination )
repulsion of insects ( nasty insect locusts )
communication ( telling the plant to flower not flower or sprout seeds )
communication between plants....

remember also that wild rosemary may not be anything like what you are using ( they identified the archetypal rose from around 1000 AD and it looks more like a strawberry plant...) - sort of like skunk and boring old cannabis sativa....

the current prog on teevee - science power proof....
seems tailor made for you.

There was one prog where the final shot ( 30s) talked about THE most successful species ( expectation : us H sapiens ) and it panned over fields and fields of triticum ( wheat to you ) - and the fact that Triticum has persuaded us to culture it world wide..... and that tastes nice !

so as you can see - I kinda did a double take on your question.

if it tastes nice it is more likely to be cultured by Man.

[Captain Spod]

See, this is why I love AB.
Impossible to choose a Best Answer as you have all put forward brilliant, cogent explanations.
I shall sleep easier now (apart from the Crossroads thing).
Night night, and thank you.
CS

[Peter Pedant]

There's quite a good fossil prog on repeat
Fossils where do they come from where do they go to?

on the Burgess shale and cambrian (fossil) explosion

[Old_Geezer]

If the leaves and stems are eaten with the seeds and they pass through the digestive system intact and end up at a new location covered in manure, it seems a very useful evolutionary adaption.

[I_Hate_Infinity]

jim360 offers the best answer I think.

You see the same is true of farmed animals (sheep, pigs, cattle, reindeer, chickens etc...) Because we have found desirable qualities of them like tastey meat, clothing materials, milk/eggs, by chance these animals have ensured their survival as a species because of our fondness of them.

Farming and gardening are the systems that we created so we could rear livestock and grow crops so we didn't need to hunt or gather and be at the mercy of wild nature, and possibley hunting and gathering them to extinction.... Anyway, pretty much what jim360 said

IHI