Can Escallion be replaced by onion?

A little research seems to suggest that escallion is not scallion :

Escallion - The escallion (Allium ascalonicum L.) is a culinary herb. Grown in Jamaica, it is similar in appearance to the British spring onion, American green onion, Welsh onion and leek, though said by Jamaicans to be more flavourful. Like these others, it is a (relatively) mild onion that does not form a large bulb.

(from Jamaica Cooking Dictionary )

Now ... 'Allium ascalonicum' is not what most countries consider 'scallions' (that'd be the 'Allium fistulosum'); ascalonicum is what we normally call 'shallots' ... so it's possible that they have a variety of shallot (aka 'multipier onion') that's bred for the green tops.

A little further digging suggests that the Allium ascalonicum L. is specifically 'wild onion', which I know I have growing in my lawn (but only really harvestable in the spring, before I start mowing for the season). It's possible that there are regional variations, but I'd say that wild onion tops are closer to chives, but that might also come from my harvesting them before they've fully matured.

...

All that being said, I substitute things all the time. I'd probably cut down the amount of onion (or use a milder red or yellow sweet onion), go with chives or shallots, or as @belisarius mentioned, go with leeks.

update: and in walking through my yard today, I noticed that the wild onions are back up above the grass, so at this time of year, you might have a free (and closer) substitute -- if your yard has areas where it looks like densely packed chives, and if you cut some, it'll have an onion-y smell, then you most likely have wild onions.

Escallion = scallion = green onion.

I think it's possible to substitute regular onions in some situations, but there are a lot of variables.

First off, scallions have a sharper, more grassy flavor than onions, though they're not as strong.

Then there's the question of which kind of onion you want to substitute. White onions have some of that same sharp flavor, and are quite strong. Yellow onions are much milder and sweeter, and might not be such a close flavor match. Red onions are somewhere in between, in my experience. I would probably try white onion, but in much smaller quantity than called for of scallions.

It's also important to consider how the scallions are being used. If they're being cooked into the recipe, that's very different than if they're being added right at the end, or even as a garnish. I think the substitution is less of an issue if the scallions are to be cooked. If they're to be more or less raw, I'd suggest white onion, not too much of it, and sliced very very thinly, as a raw white onion is really strong.

Whatever you try, bear in mind that it won't be exactly the same. But that certainly doesn't mean it'll be bad--just different.

You may "almost" replace scallions by a mix of onion and leeks. Half and half is usually ok if your onions are strong flavoured.

You can replace escallion with green onion, but the flavor won't be identical. If you're concerned with cost over reproduction, green onions are cheaper and suitable.