What does it mean to "thin" plants?
In most cases, you'll have one seed per container, seed tray cell, pellet, or seedling pot. Thinning seedlings is a common method that's used to ensure proper spacing of plants in your garden.
Seedling that are growing too close together will end up competing with each other similar to the way weeds compete with our flowers and plants! And vegetable plants that get overcrowded don't produce as much food in the long haul as the ones that have plenty of room to grow. Some seedlings won't produce any food at all!
Left "unthinned" the crowded seedlings will still grow into mature plants, but their growth will be stunted. They will become weak and leggy. Indoor seeds in particular will also suffer from lack of air circulation which causes mold in your growth trays.
Do I have to thin my seedlings? (said in a desperate voice)
This is especially true when I look at my lobelia, viola and oregano seedlings. Those plants are so tiny that I know my fingers can't handle the job of separating. If I tried to pull them out of the soil, I'd end up dislodging all the delicate roots, even the ones I meant to stay put.
The job of carefully separating crowded seedlings is boring, time consuming and pointless as those plants almost always just die anyhow. When you are trying to pull their tiny root system out of the soil, you end up yanking almost all the plants out. You're lucky if you are still able to save the one plant! What a shame if you after futile attempts to "save" plants you ended up having none at all.
The problem for me is that I'm never convinced my seeds will germinate! Even when the packet promises a 70-90 percent germination rate per seed! Such a doubter. So I end up cramming too many seeds in each pellet thinking the worst. And of course, most of the seeds do germinate and I'm back to square one again thinning them out.
So carefully follow the instructions on the seed packet. Even so, you still might have to thin them. I can't tell you how many times I thought I only put one seed per container only to discover later that several germinated. Working with small kids + clumsy fingers + teeny tiny seeds can do that!
When to thin seedlings indoors and out?
How to choose which seedlings to thin out?
If your seedlings are all the same size, then random thinning them out is the route to take. If you want to give them a few more days to see if there's a clear winner in the group, that's okay. But it probably won't be a big deal either way. Whichever plant you choose should survive and thrive as long as you thin away.
How much thinning do I need to do?
The exception is if you used some more "unusual" pots, like the plastic dome chicken containers I recommend. I just use those good ole gardening instincts when considering how many plants to keep versus purge. Works like a charm! Well. Sometimes.
Seedlings that were sown directly in the garden rather than started indoors must be thinned to the spacing requirements on the seed packet. After all, this is their final destination.
Breakin' it down - Seed thinning step-by-step!
2.) Use the right tool for the job - Pruners are too big so I used my kids smallish hair cutting scissors. I didn't want to accidentally damage other seedlings in the process. But first, I washed the scissors with mild soap detergent to disinfect them. You could also dip the blades in rubbing alcohol or wipe them clean with a cotton ball soaked in rubbing alcohol.
3.) Snip seedlings at the base. Don't worry about the roots. If you try to yank the seedlings out of the soil instead of snipping them at the base, you could damage the roots of the one plant you are trying to spare. And if you are trying to save a few to transplant to other containers then you have to be super careful here. This is true for carrots and other root crops. Sometimes when you get deformed carrots, it's due to damage done to the seedling roots when the plants were young. They never got over it....should have tried therapy!
4.) Give the remaining seedlings a little boost of all-natural fertilizer. Chemical fertilizers are hazardous and can damage seedlings by burning tiny roots. Compost tea bags are great or you could brew your own. Seedlings also love liquid kelp fertilizer or fish emulsion.
My cauliflower confession....
If the transplanted seedlings don't make it, I'm not going to sweat it. But because these seedlings were a bit bigger and not as closely planted together, I'm confident that I was able to extract them without damaging any root systems. So regardless, I'll have my original ones to transplant to the garden (the ones in the round pot.) Some seedlings are bigger than others and their roots not as spread out. I would have never attempted this with the microscopic, (or so it seems), lobelia or viola seeds. I'll keep you posted if they pop back into action and end up thriving!
My pencil trick....
I discovered that I like using a pencil to plant seeds. It makes the perfect sized hole for either planting seeds or transplanting seedings/very small plants. It's also easier to control the depth of your seed better when you use a pencil. You know how it is. Some plants want to be planted 1/4 inch deep while others are a half inch. A pencil helps you regulate the process. Works like a charm. Try it! You'll like it.