Why You Should Cull Most of Your Seedlings
My name is Lukas Wallmann of Uttendorf, Austria where I live in a tough 900 meter-high climate that is cold, windy and wet. I love to breed and test the limits of tomato resiliency. I throw away more than 90% of my seedlings- they may look good, but they are not great genetically. I normally want 1 plant per strain, most people that grow many tomatoes are only keeping one. So why are seeds packaged 10, 15, 20 seeds per package for private users? You might get the wrong idea. If you only want one strong tomato plant, you should place at least ten seeds in a small pot, close together.
All heirloom seeds are stable strains, but their genes vary a bit, they are doing so to adapt to nature. In nature, if a tomato plant dies, the fruits fall to ground. Some might get eaten by animals, but the main part will lay on the ground. What happens is they will start to rot and the seeds will stay… So there are thousands of seeds laying on a relatively small space. If they grow, some will dominate the others, maybe because they germinate first, maybe because they are a bit bigger. The ones that are smaller will not get enough light and will stay small or die. It is good that way, because the plants will inherit all information through the seeds and carry it on to the next generation. If some poor genetics were allowed to stay alive, this would kill the whole population in a few generations, because the genetics get worse each time a bad trait survives.
So what you should do is sow at least 10 seeds and allow them to grow, wait until the strongest ones show up and cull the rest. This might sound brutal, I often hear things like “A plant is a living thing, you can’t do that!” But this is the way nature protects itself and people make too much drama over it. For example, if a seed simply germinates later, and you keep that plant, take your seeds and grow them again they all will germinate later, some even later yet, and if you take seeds from these, they will germinate even later, and so on.
If you select your seedlings in this manner for several seasons, you will see a large improvement in the strain. It will germinate faster and grow better. The seed will also save information on how it was treated, don’t spoil it a lot. If you water six times a day and give some seeds to a friend that waters once every two to three days, this will be a problem for him. It could also be a problem for you, if you can no longer do that anymore. So don’t baby them too much, think about simulating mother nature. It does not rain every day, and sometimes there is drought, or too much water. If you simulate mother nature on the more extreme side, you will harden the strain to that given situation, providing a stronger plant for future generations.