Aug, Sep, Oct
Choose a couple of healthy tomatoes and mark them with a tag, so you don't pick and eat them by accident.
When the tomatoes are very ripe, pick them off the plant and cut into them over a plate.
Scrape the tomato seeds out into a glass jar and discard the flesh. Cover the seeds with water.
A mould will develop after about four of five days. This helps to remove the gelatinous coating on the tomato seed, which can prevent germination.
Pour the seeds into a sieve and wash thoroughly with water to remove the mould. Arrange them on a plate or piece of kitchen roll to dry.
Once the seeds have dried out, store them in a paper envelope in a dark, cool place until spring. Make sure they are clearly labelled.