[Daisy]

I have loads of nectar rich plants in my garden. So why is it that all the butterflies ignore everything, except the Verbena bonariensis?
This plant is clearly the creme de la creme and the Top of the Pops as far as the butterflies are concerned.
The bees and hover flies, love it too, but they will also collect the nectar from the other plants as well.
But not the butterflies. Only the Verbena bonariensis will do for them. 
Daisy

[MikeHardman]

Daisy - nice!

You've done well to photo the swallowtails, especially atop those tall verbena, probably swaying in the breeze.

I've watched swallowtails feeding in my garden and it seems to me they tend to keep fluttering while feeding; I've wondered why; perhaps their weight might bend the flowers down. When they are ovipositing, they are much calmer. But anyway, nectar is obviously a very rich source of energy - some butterflies (and moths) do a lot of flying versus the amount of time they spend nectaring. So one might argue that their high-octane fuel allows them the luxury of being fussy - perhaps ignoring some flowers nearby for others further away. And if those further flowers are the best nectar source locally, then so much the better.

I think there are lots of aspects of lepidopteran feeding behaviour that we don't understand. How does a butterfly remember which florets of which flowers it has already drunk the nectar from? (if it does). Why do butterflies favour certain flowers over others? (not just a question of ultraviolet honey guides). How do they know when to give up on the flowers in one locality when another locality is becoming more nectariferous (if there is such a word)? Many such questions assume a certain efficiency in their behaviour, which may or may not be valid.

I do not know the real answer to your question, Daisy.
But I do know that first we have to be curious, then observant, and then formulate a question. You've done all of those.

[John]

Hi, I will mention another plant that swallow tails went mad for on Crete which is the wild Heliotropium dolosum. Just by the road between Neo Horio and Agii Pandes in western Crete where this annual formed a carpet it was covered in these butterfies. This was the one time I managed to catch a picture of them.

[MikeHardman]

Yes - the small-white-flowered heliotropes are favourites of swallowtails and other butterflies. This spring, my bare soil bank was transformed into a field of these plants, and it was thick with various whites, and coppers.
As well as H. dolosum, there are H. europaeum, hirtsutissimum (of some butterfly books), etc.

[John J]

Every year the swallowtails present me with the same dilemma. Every year their caterpillers appear on my Crithmum maritimum plant. Every year I have to decide whether to allow them to decimate the plant or transfer them to something that will bear the damage better. I solved it this year by transferring them to my wife's parsley patch. With her permission, of course!!!!

[hilberry]

The swallowtail caterpillars in my garden feed on fennel, wild carrot and MY carrots. The butterflies favour the buddlaeas.  I have some good photos, but haven't worked out how to post them on here yet.  However, this year there were none, that I spotted anyway.   There were plenty of the more common butterflies. 

I remember climbing a pic in the Pyrenees to find a huge cloud of swallowtails.  What a delight!  I was too puffed to see what nectar flowers were about for them. 

[John]

John J does this mean that you prefer to eat Crithmum to parsley?

[JTh]

Both V. bonarensis and many of the Buddleias are very attractive for butterflies, I have been wondering if the purple colour is part of the attraction. I saw a reference to an article: ‘Butterflies show flower colour preferences but not constancy in foraging at four plant species’ (N. B. POHL, J. VAN WYK, D. R. CAMPBELL. Ecological Entomology, 2011, Vol. 36-3, 290–300). Only the abstract was available, so I don’t know which colour was the most desirable one.
I am sure the caterpillers are colourblind.

[John J]

I've never tried Crithmum, John, what's it like? It's just that as the swallowtails begin to lay their eggs the Crithmum is starting into flower, not spectacular I know but better than a skeleton of a plant after their offspring have finished devouring it. At this same time the parsley is past its best and they can clean up the old growth before the new stuff comes through.

[John]

Well I have to say that I can't remember ever trying it. I believe in Britain there is some sort of tradition of pickling it. It may just be cooked or added to other horta but I should try to get round to looking this up. I do have a few books on horta but not the time right now. I have to say with few exceptions e.g. celery and it's root celeriac and parsnips I don't generally like eating Umbellifereae. Certainly not parsley or coriander.

[hilberry]

I have a buddlaea weyeriana [yellow] that the swallowtails like as much as the purple one.  It's an untidy shrub, but flowers for 8 months of he year.

[John J]

Having consulted my copy of Georgios Hadjikyriakou's book 'Aromatic and Spicy Plants in Cyprus' I see that Crithmum maritimum (Samphire, Sea Fennel, Peter's Cress) has a long history of being eaten. Dioscuridis wrote that their '...leaves are similar to those of purslane, but broader and longer and with a salty taste,...it is eaten as a pot-herb boiled or fresh; it is also pickled in brine'. Apparently the young, fleshy leaves are still pickled and used as an appetizer and salad ingredient. I'm still not tempted.

[JTh]

We have a lot of it on our beach and I have tasted it, it was slightly salty and bitter/sour; not bad, but not my favourite either

[David Bracey]

Rock samphire is sold in France ( and now a days even in the UK) to be eaten with shell fish and fish.  It is eaten raw and is delicious along with coriander and parsley.  How can you be serious and not like parsley or coriander let alone samphire. David

[John]

I am serious, I suppose it's a taste thing. Personal taste that is!