Allium
Onion
Allium cepa
Plant sets in March, harvest fat globes in August.
Full sun
Moderate
Well-drained
Easy
Yes
Bulb
Biennial
Hardy
5 L
15 cm
Root
Carrot
Onions repel carrot rust fly and carrot weevil through sulfur compounds while their shallow root zone avoids competition.
Root
Beetroot
Onions repel root maggots and thrips while their sulfur compounds suppress soil-borne fungal pathogens affecting beetroot.
Leafy green
Kale
Onions' sulfur compounds repel cabbage loopers and other brassica pests while kale's density suppresses onion-damaging weeds.
Situations where this plant is a reliable fit — from someone's kitchen sill to a wind-blown rooftop.
Balcony
A few pots on a flat outdoor perch — some sun, some wind.
Ladder planter
A tilted step-ladder with a shallow tray on each rung — sun-facing, five tiers of herbs, salad and strawberries in the footprint of one pot.
Wooden crate
A shallow wine or veg crate lined with hessian — perfect for salad and shallow-rooted herbs.
Raised bed
A traditional plot or timber-sided bed — deepest root run, widest planting choice.
Water jar
A jam jar of water on the sill — no soil at all. Regrow from kitchen scraps.
Recipes in the library that lean on this plant. Grown at home is grown for a reason.
Root in water, transfer to soil
30 days
★★★☆☆
Yes
How to do it
Use a sprouted onion from the cupboard. Slice off the bottom 2 cm with the roots intact, stand in 1 cm of water for a week, then plant in a 20 cm pot of compost.
What to expect
Green onion-flavoured shoots (use like spring onion); rarely produces a full bulb again.
Honest note
Honest rating: this is a green-tops crop, NOT a way to regrow whole onions.
Where to source
Get growing in United Kingdom
Shop local first
The best plants come from a real nursery, and the best trowel comes from the old-fashioned ironmonger down the road — people who know their stock and can advise. Try local first, both for the plant and the kit. It keeps small growers and small hardware shops alive.
Searching near London
For pots, compost, seed trays, twine and other kit — Amazon has the essentials if the local option isn't right. Not a plant nursery; use the local map above for the plant itself.
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