Seedling Thinning Basics

[applestar]

Can we do a thread dedicated to thinning seedlings? If we get a compilation of useful details, this can be made into a stickie.

At the very basic level, you always want to SOW only 2-4 seeds per cell and/or place seeds so that they are at least 1/4-1/2 inch apart. In a community pot the groups of seeds could be about 1/2-1" apart.

You then almost always thin to one per cell or every 1"-2".

Sometimes you thin by leaving one and clipping off the others at soil level.
Sometimes, you can gently dig them up ("prick them out") pull them apart and re-plant them separately.
Often this depends on what kind of plant and/or how closely they were growing to begin with, and how big they are.

It would be good to go into specifics of what can tolerate fairly rough handling -- be it naked roots or broken off roots, and what needs premier treatment with plenty of soil cushioned around the roots at all times.

Beets and Chard come up several seedlings per seed capsule and they are notoriously prone to getting uprooted if you pull on their sibs. But I understand they need to be thinned fairly early on. So do you clip the culls at seedleaf stage or do you let them grow true leaves first?

I also want to ask about thinning when seeds are sown directly in the ground. Same principle applies -- few seeds every so many inches apart (in rows so many inches apart), or broadcast -- and thin. Surely, you don't painstakingly pull or clip them individually like you would with indoor starts. But it seems wasteful to draw a hoe over them all. Should you wait and dig up and transplant after true leave grow or cut them as micro-greens and eat them? What about carrots? They need to grow quite a bit before they have any serious baby carrot roots to them.

What kind of tools do you use?

So, who wants to start?

[gumbo2176]

I consider myself a pretty frugal person when it comes to plants, seedlings, etc. For my lettuce, beets, chard, kale, I'll flatten the top of one of my rows, make two or three shallow furrows and place the seeds in the furrows and cover with the soil, tamp it down a bit and water them in.

After the plants emerge, I'll wait until they are a couple inches tall and have their true leaves then I'll separate them to proper spacing and transplant as needed. I'll use a small garden hand shovel, dig a couple inches from the starts and go down deep enough as to not cut roots. Then I'll painstakingly pull them apart and transplant. Lettuce takes to this with little loss, beets wilt a bit more and for a longer period but have bounced back. Chard and kale are real hard to mess up and transplant with ease.

If I start things in seed trays or 2x2 inch cells, I'll generally place 3-4 seeds in each cell, spacing them a bit. After they come up, I'll cut out the weaker plants with scissors. I did this with Juliette Tomato seedlings and they are ready for the garden to keep my Creole's already in the ground company.

[digitS']

There are two problems for which I have found reasonably good solutions.

The agony of destroying an otherwise healthy seedling : No matter how small it is - tiny, right down to the size of a dog hair - I carry it off to the compost. The plant then has served a purpose much as cover crops serve a purpose in the garden.

Pulling the neighbors out of the ground : When I thin more established plants in the garden, I try to drag the plant in a horizontal fashion rather than lift it straight up. If there are entangled roots from those plants that will remain, this horizontal extraction seems to just displace the roots of the other plants a little. This is not the best way to take out something you may want to transplant. Being drug out of the soil sideways doesn't leave the thinned plant in very good shape. But, off it goes to the compost.

Steve

[jal_ut]

In thinning outdoor planted things, do it when the plants are small about 2 inches tall. If you wait longer, you will damage the roots of those left by pulling some out.

I have had good success transplanting corn, cabbage, broccoli, and lettuce. I usually plant cabbage seeds about 4 inches apart then transplant some to another row and space them 18 inches. In the original row they will end up 18 to 24 inches apart. Broccoli seems to do OK if planted a bit closer.

Sometimes corn comes up patchy, so I will move some of the close ones to the open spots just to fill in the gaps.

Lettuce often comes up volunteer and first thing, so I will move some to a row rather than having it just at random where I want to plant something else.

With all of these things I just use a garden trowel and dig a hole first then go dig up the plant being careful to keep as much soil as possible on the roots then go set it in the hole and compact soil around it then water it. The success rate is very good when the plants are about 2 inches tall.

Seed is quite pricey these days, so I have taken to being much more frugal and placing the seed about as thick as I want the plants to be rather than just throwing some in a furrow and later thinning 80% of it. If I want one plant in a seed starting cell, I put one seed in. If I want radishes to grow 2 inches apart, I put a seed every 2 inches. Yes, they never germinate 100% but its OK if they don't. Those that do germinate will make a harvest. None get wasted just because they were too close.

Beets, seem to always need thinning. It is the nature of the things since the little capsule has several seeds in it. It is best to clip those you take out instead of pulling so you don't damage the roots of those left.

[rainbowgardener]

Starting seeds indoors, I put the large seed things like squash one to a cell. The things like tomatoes and peppers, I plant 2-3/ cell and then transplant. But then there's things like petunias, impatiens, spearmint, etc with seeds like dust. I always end up with a whole bunch of them in a cell. Since I hate throwing plants away, I do transplant most of them.

What works for me with really crowded things like that is to lift the whole bunch out of the cell together - run a wide plant label stick or something down the side of the cell and then lift from the bottom.

Once they are out of the cell, you can gently tease the plants apart with a toothpick or the narrow end of a plant label stick. The advantage of this is that you can then see all the little root systems. It's a better indication of which ones are healthiest. So then I plant all the ones with nice healthy root systems and yes, toss the rest (compost).

I do keep a little bucket by my seed starting operation for all the swept up dirt, little sticks that come in the potting soil, plants that are culled, etc, to be emptied in compost later, so that I don't have to run out to the compost pile with one little seedling. But I don't waste anything!

[applestar]

rainbowgardener's bigger root system to keep is a good indicator of what to keep. What about the upper growth? Bigger seed leaves and thicker stems?

When culling by clipping, and the leaves and the stems look about the same, I clip the taller ones and keep the shorter ones.

Most of the time, if I have to choose, I cull the mangled seed leaves and keep the perfect ones. But this time I had an Arkansas Traveller tomato with poor germination and one of them looked like a stub - NO seed leaves at all -- just a slightly thickened tip to the hypocotyl. I kept it anyway and gave it it's own tiny pot when I separated and uppotted the rest, and gave it a place under the lights with the rest of 'em. Well guess, what, the little champ has been growing true leaves from the side of the lumpy tip.

[digitS']

Good luck with that little champ, Applestar.

Tomatoes are different than some plants in that they can grow roots along their stems. They are also - nearly clones of the parent plant since offspring are usually a result of self-pollination. Your champ may have nothing genetically wrong with it, Applestar - a physical problem may have started it off wrong or, maybe, the seed wasn't quite mature.

Having said that - I am often disappointed in how weak sisters perform. Usually, I transplant out of a container into cells. Weaker plants go into the compost or they are separated from their stronger sisters. My experience has been that those plants never perform as well thru their lives.

It is performance that we are hoping for in the garden, altho' sometimes a plant is just wanted to produce a few valued seeds. However, simple survival isn't usually what we are hoping for. Robust seedlings usually are robust garden plants and robust garden plants usually produce what it is that we are looking for - beauty or something to take into the kitchen.

Culling out the weaklings may keep us gardening . . . having an unproductive garden isn't much of a trick . . . and, growing a hodge-podge of over-crowded plants is just a recipe for poor results.

Steve

[SPierce]

For me it could go both ways, and I've learned never to underestimate the underdog- of course, I am very small so I have the room and the time to let what others would throw out go for a little bit longer.

I currently have a pepper seedling in which I accidently knocked off (literally) the top where the seed leaves come from. I kept the roots in the ground of the pot just to see what would happen- and it's growing taller/starting to grow seed leaves!

Also, out of 4 zucchini plants from last year, 3 of them looked very strong/thick, so I planted them in the ground- while one looked fairly thin and weak. I hardened them all off, and decided to plant the "weak" plant in a container. While my 3 stronger plants didn't produce any zucchini at all, the weak one kept going strong and producing a LOT of zucchini untilI pulled it after a hail storm. I'm pretty sure it was about 2 feet long and 4 feet wide.

[rootsy]

For beets grow the new monogerm varieties such as Solo...

[jal_ut]

Posted: 03 27 12 Post subject:
Starting seeds indoors, I put the large seed things like squash one to a cell.

Squash (and cukes) will do much better planted directly in the garden where it will grow. They do not appreciate their roots being messed with, and growing them in a container for any length of time just makes their roots curl around in circles when they should be going somewhere. I dare to bet you can plant a seed the same day you put a start in the garden and the one started from seed where it will grow will do better in the end than the one started in a pot and transplanted.

Onions, on the other hand, can be grown for a while and yanked out and shipped from Texas to Utah bare root, then planted and they do very well.

I have pulled cabbage plants, (bare root) then planted them and watered them. Doing that they will wilt right down and lie flat on the ground for one day, but they usually recover and stand up the second day. Most other plants are not this resilient. I prefer to dig plants and keep a rootball intact if I can, but sometimes it doesn't work out that way.

[soil]

I eat most of my thinning plants.

as far as what to thin it all depends on the species of plant, the method of propagation/production,soils involved, and desired end product.