Compost enriched with worm castings for transplanted plants

On a long crop, such as a tomato grown from May to September, the reserve in the potting compost only covers the start. You then take over with Bio-Grow, at 2 ml per litre on this rich compost, then add Bio-Bloom when the first flower clusters appear. Before each round of feeding, a drop-based pH test tells you whether the watering water stays between 6 and 7. The worm castings that enrich this mix are the same amendment as that produced by a worm composter, as the article on vermicompost explains.

Let the potting compost dry on the surface between waterings. This cycle draws fresh air into the grow medium each time the water drains away, which the roots and micro-organisms need just as much as the water itself. A pot watered while it is still heavy stays saturated, soil life slows down and the roots turn brown. Weigh the pot in your hand rather than following a calendar: a pot of 10 litres of damp compost weighs noticeably more than one that is ready for watering, and you quickly feel the difference. In summer, in a greenhouse, the rhythm can become daily for fruiting plants in full production.

In an aquaponic system, the roots sit in the fish water and draw up the nitrates produced by the filter bacteria. The grow bed therefore needs a inert, pH-neutral medium that does not alter the water quality, such as volcanic gravel or clay pebbles. A peat and humus compost meets neither of these conditions: the organic matter breaks down in the circulating water, clouds the pond, clogs the pipes and adds an organic load that the filter has to deal with. So keep All-Mix well away from the fish circuit.

It does, however, find its place alongside the system. Plants that you do not grow in a grow bed, such as trailing squashes, potatoes or fruit bushes, do well in large containers of rich potting compost. Plants intended for the system are started instead in an inert medium, in a slotted net pot filled with rockwool or coco fibre, then move into the grow bed about two weeks after their first true leaves, with no soil clinging to the roots. Worms, finally, are also used in aquaponics, but live in the grow bed, as the article on vermiponics explains.

The 20-litre bag weighs about 5 kg and fills two 10-litre pots or one balcony planter. The 50-litre bag, at about 13 kg, fills a vegetable bed or five 10-litre pots for tomatoes. Keep the potting compost in its resealed bag, sheltered from frost and full sun, so that its microbial life stays active until use. The remainder of an opened bag can be reused to top up the surface of pots during the season, or mixed into a tired potting compost to restore its vigour before a new planting.