Presumably only a few hobby gardeners want to multiply onions themselves. After all, there are plenty of seeds and onion sets to buy at affordable prices. If you get ambitious, you will make it with these instructions.
There are two ways to propagate onions yourself. The first option is to grow onion sets from purchased seeds and plant them in the spring of the second year in order to harvest large onions in the fall. The second option requires more effort and takes a gardening season longer.
The seeds are harvested in the first year, and the onion sets in the following year, which can grow into large tubers in the third year. The individual steps are described below. If you want to try the simpler option first, please start with step 2.
1st step: Harvest seeds
As the young bulbous plants grow, some of them form inflorescences. Normally, this bolting is not desired, since in such plants the flower develops instead of the tuber. However, if the plant is allowed to flower, the flower will later form a seed pod from which the seeds can be harvested. These are germinable for about 3 years.
Then proceed as follows:
- in autumn harvest the onion with the inflorescence like all other onions
- hang them upside down to dry out, possibly tying a paper bag over the inflorescence
- Store the dried inflorescences in a cool, dark place until next spring
- a month before sowing, store the inflorescences at temperatures of 25-35 °C
Step 2: Harvest the onion sets
The self-grown seeds are sown so densely that onions the size of hazelnuts can develop from them. Once they have reached the desired size, harvest the onion sets and let them dry thoroughly. They are stored in a cool place over the winter and kept warm (25-35 °C) for about a month before planting.
tips and tricks
To separate the good from the bad seeds, pour them into a glass of water. The shells and "empty" seeds remain on the surface while the good seeds settle to the bottom of the glass.