Cosmos (Cosmos bipinnatus) is a favourite of mine. Under the right conditions, they can be light and ethereal, with starry flowers that live up to their name – like white, pink, mauve and cerise constellations.

Rotten things.

“Right conditions” means that they grow better in sidewalk cracks than they do in my garden.

When too well-fertilized, such as when they’re growing in the average flower garden, cosmos pump up the foliage. The flowers can look like tiny heads on a huge body. Sidewalk cracks give them just the paucity of soil they need to create the ideal ratio of foliage to flower.

Cosmos fall into the category of hardy annuals: annuals that reliably self-seed even in our wintery climate. Self-seeding is how they end up growing in sidewalk cracks in the first place. They’re like nature’s guerrilla gardeners. I’ve seen California poppies (Eschscholzia californica) and purple coneflower (Echinacea purpurea) do the same. I suspect the cooler, moister root zone, protected by the concrete or cobblestones, has something to do with the way they thrive.

It isn’t often that you see the pure white cosmos – perhaps ‘White Sensation’ – popping up, as here. Usually, these happy self-seeders cross-pollinate until all you get are the pale mauvey-pinks. Not that it’s a bad colour. However, I always like to see them punctuated by the full variety of shades, with a strong showing of the whites and deep cerise flowers.

Grow in a crack, break your mother’s… heart. But, bloom on, cosmos. That’s all right with me.