This definitely counts as cheating at gardening.
This is not a secret. I am not the first person to suggest this, out on the internet (I probably got the idea from somebody else, to start with). But I figured it was worth passing on again, for people who do not already know:
It is really, really, REALLY easy to grow spring onions by cutting off the root bits of a store-bought bunch, and planting them into some potting mix.
I mean it. Cut off the root bits of the spring onion, leaving about 3cm of stalk, stick the root bits into some potting mix with the stem-bits poking out above the surface, place in a somewhat sunny position, water, and watch 'em grow. New edible leaves will begin emerging immediately, and be ready to eat within a couple of weeks.
Considering you probably buy bunches of spring onions all the time for eating, and probably cut the root-ends off & chuck them in the compost, this is basically NEW PLANTS FOR FREE.
I've done this at least 3 times, and it's always been successful. One batch got left behind when I moved house, one batch eventually flowered, and one batch is still going a year later (although a little straggly now because the potting mix they're in is old and infertile now, and nobody remembers to water them- but still, they grow!).
So I should probably say things like: look for fresh, healthy spring onions, and ones where the roots look nice & intact. But to be honest I've never seen it make a difference. I've grown new plants from manky spring onion bunches that were already old & tired looking at the grocery store, and then sat in a dodgy sharehouse fridge for a week.
Compared to growing from seed, this method is a total winner. The few times I've tried starting spring onions from seed they took forever to come up, then came up as pin-thin strands that grew oh-so-slowly, and weren't even close to being table-ready when some ravenous slug or snail turned up and ate the whole pot-full of them. It was a recipe for frustration. This method made me much happier. Hooray for fast returns!
This post today was inspired by my passing this tip on to my parents yesterday at the greengrocer ("you should grow spring onions. In fact, you should grow them from that bunch you are buying right now"). As you can see, they have now planted the root-ends of that bunch, and are hopefully well on their way to a never-ending supply of fresh, free spring onions.