For houseplants in old compost that has run out of goodness, so new leaves come in smaller and paler than the last. Worm castings are the gentlest way to bring a tired mix back: a natural, slow-acting fertiliser that also brings life back into the soil. Mix a handful into fresh potting soil, or scatter it over the top of a pot you'd rather not disturb. 3L resealable bag.
Castings are what earthworms leave behind once they've worked through organic matter: fine, dark and crumbly, with almost no smell. They release their nutrients slowly, through the microbes living in them, so there's no sudden rush of feed and no risk of scorching roots. They also help the soil hold water and keep a looser, more open structure. They're one of the main ingredients in many of Sybotanica's own soil blends. These come fresh and are still alive, so you may find a few worm eggs or the odd small worm in the bag. Both are harmless to your plants.
How to use
- In a new mix: stir a handful or two through fresh potting soil before you repot, or blend it into our Base Soil Mix when you're making your own.
- As a top dressing: scrape away the top centimetre or so of old soil, add a thin layer of castings, and water it in. It's an easy spring refresh for plants that don't need repotting yet.
- Use it fresh. Castings are at their best within about six months. Keep the bag closed, cool and out of the light.
At a glance
| What it is | Worm castings (earthworm humus), a natural slow-release fertiliser and soil improver |
| Origin | Netherlands |
| pH | About 6.4 |
| Organic matter | About 31% |
| Lasts in the soil | 2–4 months, depending on watering and what it's mixed with |
| Volume | 3 litres, resealable bag |
- Suitable for organic growing.
- Listed by the maker as pet safe. Still, store it where pets can't get into the bag.