Last year was the warmest March on record: this year it has so far been the coldest. Spring ain’t what it used to be. None the less, it’s reliably time to harvest the ‘spring onions’.
I don’t mean the things you buy in the shops as spring onions (or scallions) since I don’t grow them. Let’s face it, onions are a pain to grow from seed. You need lots of added soil fertility and fanatical weeding of things that look regrettably similar to grass seedlings. Then, just as they are starting to look after themselves, you dig them up and eat them. By this time it’s usually August, which isn’t spring, not even here in Aberdeen.
Fortunately there are two perennial vegetable species which produce excellent spring onions even when it’s still snowing and with very little fuss for the rest of the year: tree onion (Allium cepa proliferum) and welsh onion (Allium fistulosum).
Tree onion is the same species as the ordinary onion. A lot of allium species can produce either flowers or tiny bulbs called bulbils (or both) in their flower heads and tree onion is a kind of onion that goes for all bulbils. These often sprout when they’re still on the plant, giving it a tree-like appearance. The stem then usually falls over, giving the plant another of its many names – walking onion – as the bulbils put down roots and the plant ‘walks’ around the garden. It also reproduces by bulb division underground, like a shallot or a daffodil.
This gives two ways to exploit tree onions for spring onions. First you can dig up the parent plant when it resprouts in the spring, divide out some of the bulbs and replant the rest. The other way is to gather the bulbils when they are produced later in the year and plant them out into a bed where they will grow on into very well shaped spring onions. It’s kind of like having a free supply of onion sets for spring onions and yet another name for this plant is ‘topset onion’ (You can also let them grow on into bulb onions, but they tend not to be very big.). You can plant some in the autumn for spring growth as they are extremely hardy but they will also keep well if you store them in a cool, dry place, so you can make successional sowings later on in the year too.
Welsh onion is a different species from regular onion but it’s very similar to tree onion. Instead of bulbils it produces a rather fleshy flower head which can also be used as a flavouring or left to produce seed (picking the flowers stops the plants producing seed and diverts their energy back into making bulbs). Like tree onions they divide underground and can be lifted and divided as spring onions in March and April.
Both species can also be harvested by picking leaves in the summer. I find that welsh onion makes bigger and more regular-sized spring onions by division and tree onion is better for leaves, partly because you can use the bulbils to produce a really dense patch. So the best use is probably welsh onions for division in the spring and tree onion for leaves and sets for growing on. If you allow welsh onions to flower you will be very popular with the bees.
Real spring onions can be used in all the same ways that you would use the seed-grown ones. My favourite is spring onion sambar: you fry a large handful of whole spring onions until they are soft, then add tamarind, coconut and spices to make a sauce and simmer for a few minutes. It’s a great way to forget the sleet driving at the window.