Recarbonize the world
Exploring Biochar for carbon sequestration

Seed Compost Biochar

Tomatoes in Biochar

I made up a biochar compost a few months ago using crushed hardwood charcoal at about 10% to 15% by volume, leaf-mould, blood and bone fertiliser with a little mycorrhizal fungi. On inspection I decided it was a bit too glutinous, so I added some horticultural sand to make it more seed friendly.

The seeds I decided to sow are tomato, rocket, sweet and chilli pepper, lettuce, leek and broad-bean.

  • Tomato varieties; Tigerella, Money Maker, Golden Cherry, Gardeners Delight.
  • Pepper varieties; Long Red, Bell (mixed), Long red Chilli.
  • Lettuce; Little Gem and ‘lambs lettuce’.
  • Wild Rocket.
  • Leek; Blauwgroene Winter – Bandit.
  • Broad Bean; Saved seed, longpod.

The Tomatoes were sown on the 15th March and put in a propagator. The germination was good with only a couple of duds among the saved Golden Cherry seeds. Once they emerged the rate of growth was rapid so I removed them from the propagator and potted them on, planting them deep so that they grow more roots from the buried stem. I used the biochar mix when potting on. After a week on a south facing window sill, roots were already emerging from the base of the pots so they were potted on again. On day 17, the average height is 20cm.

Peppers are slower to germinate, a few of each are just showing. They are in a propagator.

Lettuce are beginning to germinate but they are not in a propagator. Some are in a greenhouse and some are in a north facing conservatory.

Wild rocket came up within 24 hours in a propagator so to stop them getting too spindly they were removed from the heat. They are still at the primary leaf stage. As soon as they form true leaves I will plant them out in the greenhouse.

The leeks were sown in deep pots fairly crowded. The plan is to wash the soil off and separate them as they are planted out on the allotment. They are about 2cm tall after 17 days in the greenhouse.

Broad beans have been slow, only one has broken the surface after 17 days in the greenhouse. The seed may not have been very viable.

It is early days but the tomatoes are showing promise. Once the weather warms up a bit I shall plant some directly in the greenhouse soil that has already been charged with biochar and blood and bone fertiliser. I shall plant them deep, up to the first true leaves to encourage more root growth making them more resilient to watering fluctuations.

to be continued, assuming the seeds grow.