Seed bombs are balls of (you guessed it) seeds – usually wildflowers – held together with clay and compost. But what are they for? How do they work? And how can you make them? This essential guide to seed bombs will answer all your burning questions about these pocketable guerrilla gardening tools.
What are seed bombs?
Seed bombs are a staple guerrilla gardening tool. They're subtle, pocketable pellets that you simply throw to grow – letting you plant anytime, anywhere (with no time, effort, dirty knees, or unwanted questioning needed).
There's a bouquet of reasons this is a great thing to do: wildflowers support our key workers – pollinators – in turn supporting the wider wild ecosystem; they keep soil stabilised and nutrient-rich; all while bringing mood-boosting colour to otherwise grey areas.
How do you use seed bombs?
You don't have to plant seed bombs; just throw them onto some exposed soil as you walk, cycle or drive around, and let nature take care of the rest.
Spring and autumn are the best times to use seed bombs. There's enough rain, and the right amount of sun to help the seedlings grow without scorching them. Check the recommended sowing months of the specific seeds you're using to find out when they most like to be scattered and sown.
Where should you use seed bombs?
Neglected street planters, tree beds, roadsides, roundabouts, and vacant lots are all great targets. If no one's looking after them, you know that no one's going to come along to strim down your seedlings. If they're too bare, beware, they may be being sprayed with herbicides (which would kill your seeds). So look for soil with some signs of life.
How do seed bombs work?
The clay holds the ball together until it gets rained on.
Then, once the bomb has met rain and sun, the seeds will begin to germinate as the ball breaks apart. The compost the seeds are encased in helps them get started before they root into the ground, and chilli powder can deter any creatures from nibbling on the seedlings.
How do you make seed bombs?
This is a tried and tested seed bomb recipe that will produce about 50 small seed bombs (depending what size you roll them).
You will need
Large mixing bowl
1/2 cup powdered red clay
50ml water
1 cup peat-free compost
Fork (optional)
1 tsp chilli powder (optional)
2 tbsp native wildflower seeds
Cardboard box
Method
Pour the clay into the mixing bowl, breaking up any lumps with your fingers.
Add water in bit by bit, mixing with the clay until it forms a paste-like consistency. You want as little water as possible so that the clay holds firm. Too much water means the seed balls will take too long to dry out, and make process of making them a lot messier!
Chuck in the peat-free compost and mix it together with the clay thoroughly. This can be tough work – pushing through the mixture with a fork can help integrate the two.
As an optional step, you can add chilli powder in at this stage, and combine it into the mixture. This will deter squirrels and the like from eating your seeds.
Shake in the native wildflower seeds and gently distribute them throughout (no fork at this stage – it could crush them).
Take small lumps of your 'dough' and roll it into balls around 1 inch (2.5cm) in diameter. As you make them, pop your seed bombs into a cardboard box (where they will dry out).
When they're all done, close the box's lid and leave it in a warm, dry place for 1-2 days. The quicker the balls dry, the less likely the seeds are to germinate. If they do start to germinate, no problem, just make sure you get them out onto some soil ASAP.
Now you're ready to leave bright bursts of biodiversity in your wake – no time or effort needed! Simply keep your seed bombs by the door so you can grab some whenever you head out, or carry a tiny pouch of them in your pocket, and you can grow on-the-go.
Tick, tick, bloom!
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Won’t the seeds be overcrowded as they germinate all in one spot?