Is it mainly to weed out the weak ones and just replant/repot the stronger ones

No, it is for stimulating root development while slowing top growth.

Search out the recent post titled "Question for Carolyn" for all the details and links.

Skipping potting up stages may be easier on the gardener but it isn't as good for the plant. ;)

Dave

From that post--

Yes, if you removed all the soil from the seedling in the 4 inch pot and then planted it outside it should form a fibrous root system.

I transplant young seedlings directly into the garden...I don't waste my time with transplanting into containers to watch them grow some more and transplant again and again before they go into the garden. It's a pointless waste of time.

Go for the longer taproot to precvent much of the issues associated with inconsitstant watering or drought.

To each his own of course, Trudi. But it is hard to dispute the photographic evidence in the article linked in the post.

One need only compare for themselves the difference in root development between 2 of their own plants - one transplanted and one not. After 1 week, carefully pop them out of their container and look at the root ball differences. It's very convincing.

Dave

I'm deeply confused. The article Dave links to is not terribly easy to read, but it says:
--%--
Since the root system is disturbed and the development of the plant more or less checked at each transplanting, it might be concluded that plants grown from seed sown directly in pots or other containers would grow more vigorously and give a higher yield than those once or twice transplanted. In fact this has been shown by numerous investigations to be the case. That transplanting in itself does not promote an early crop nor an increased yield has been also clearly demonstrated.
--%--

So, why would I transplant? Or am I misreading this?

Not misreading Mark, just noting different goals. If your primary goal is early production then likely stage transplanting would make little if any difference. But in this case the primary goal is not early crop or increased yield (although that is a secondary benefit of healthier plants).

The goal of stage transplanting is sturdier, healthier, longer-lived plants better able to resist disease and better able to absorb soil nutrients, moisture, and oxygen via a fibrous root system rather than a single tap root. The expansive root system that comes from transplanting is in balance with the amount of top growth so better able to support it. It also makes them more tolerant of shallow growing conditions such as raised beds and containers where a long tap root would be in trouble.

An additional benefit of the transplanting is to slow top growth as I mentioned above. This is especially important to those who start their transplants way too early and need to slow them down. It helps prevent the 16" tall seedlings with the root ball of a 4" plant that so many find themselves dealing with - the ones that now have to be trenched into the garden rather than just planted.

I hope this helps clarify it a bit but please keep in mind this only applies to plants you grow from seed yourself. If you buy nursery plants they have already been stage transplanted at least 2x, possibly 3x so it isn't necessary with them. That's what convinced me years back - comparing root systems, life span, disease problems, production, etc. at season's end of nursery bought plants versus those I grew myself but never transplanted.

Stick with what works for you but as time allows, experiment with and compare other approaches too. ;)

Dave

Heck some of us just like to play in the dirt more often.

Patrick - Shreveport, La.

Think of it this way..when you're born ..you wear diapers..when ya get a lil older ya wear big boy/girl pull up pull down diapers..when ya graduate,,ya wear underwear..
I know..bad comparison..but young seedlings as they grow, as I do it, get bigger they get transplanted into a lil larger container..and as they grow,,another home..
The final result is a healthy plant..that was hardened off ready for life out in the real world.

But as Dave said..to each his own and what works fer ya..

One of the reasons for changing pot sizes in stages rather than going for the big pot right away is the difficulty of taking care of many large pots. They take up lots of space, and it is cheaper to have a smaller area to take care of in the early stages of seedling growth. Less cost for lights and heat. As my pots get larger I have to turn on more sets of lights to cover the larger area.
Bob B.

I do it mainly for the energy/space and labor savings.

Dave & Trudi, new to growing myself, I'd love to engage you both a bit more on this topic with regards to winter sowing. I think I read you're experimenting Dave? do you plan to repot your WS toms too?

Though I haven't pulled up any of my WS toms yet to see their root systems, I actually had to plant my cosmos and nasturtium out yesterday as their root systems threatened to overtake my entire flat of 72 cells, though the cosmos were only wee little 'uns all of 2" high and one set of true leaves, they had roots 6" long on them. I don't know enough about gardening to know if this extensive root system is normal for all plants, or enhanced by the WSing.

So, as I read in regards to maters, the purpose is to disturb the tap root to encourage it to become more fibrous...

So then,in theory, rather than going through the expense and labor of starting a seed in one pot, only to have to repot up larger, why not take the seedling and just repot it in its own larger pot?

For instance, I sowed all of my seeds in 16oz solo cups, rather than potting to something else, could I just disturb the plant by taking it out of the cup, and then repotting it back straight into the same cup? Would that disturbance suffice, or do the root systems need to become crampt and then given room to roam?

I realize there may be many more reasons of convenience for people to start small and pot up, especially when growing indoors and using heat mats, etc... So I'm just asking purely on a theory basis.

Sorry to be playing devils advocate here, but I'm intensely curious about this and have been considering repotting, or rather, my intention to not repot since last year when I decided to buy all these seeds and give WS the 'ol college try : )

since I have to repot some of the ones that have 2 or more plants growing in the same cup, maybe I should keep notes and see what develops.

Curious to hear your feedback though!

thanks! -buck

There is positively proof seedlings have setback every time you pot up or out. So the less you repot the better.

First, I'd like to say that I have always encouraged people to follow their hearts in their gardens...you start by doing what you feel comfortable with and then you tweak that based upon your experiences.

Personally, I have no stomach for coddling seedlings because it weakens them and I don't want extra work now or anytime later in my garden. I never re-pot any of my seedlings as for me that's a waste of time.

My tomato seedlings go into the ground at around this size.
{{gwi:382756}}
They are quite tolerant of cold but initially I need to protect from slugs and snails which are prevalent in my damp coastal climate. If you look at the link below you'll see how to do it--it's very easy to do, very fast to do, and as reclycled water bottles are used it won't cost you a nickel!

Here is a link that might be useful: {{gwi:382756}}

with regards to winter sowing. I think I read you're experimenting Dave? do you plan to repot your WS toms too?

Hi buck - yes I did. I let them go longer in their milk jug (2 sets of true leaves) than I normally do those done in seedling trays (I normally transplant at about the cotyledon size in Trudi's picture above) and I only transplanted them 1x rather than the 2x I do with the greenhouse grown plants. She doesn't like coddling and neither do I - it kills plants. But then I don't consider stage transplanting to be either coddling or a waste of time. ;)

I don't know enough about gardening to know if this extensive root system is normal for all plants, or enhanced by the WSing.

For the most part it is normal for cosmos, they are rooty buggers but it is likely enhanced somewhat by WS too. If the weather permits planting them outside by all means do so. Mine doesn't yet so I would just transplant them to a larger cell/cup.

So then,in theory, rather than going through the expense and labor of starting a seed in one pot, only to have to repot up larger, why not take the seedling and just repot it in its own larger pot?

Crucial point. Many of us don't start our seeds as you did. If I was to use a 16 oz. cup to germinate seeds in I'd plant at least 15-20 seeds in it, not one. But I wouldn't use one as it just wastes soilmix and makes it much more difficult to heat the soil up and maintain the proper temps for germination. I use shallow seedling trays with no more than 1-1 1/2" of mix in it to start 100's of seedlings - on average 25-40 in each section in the pic below. Easy to heat, better germination rates, and faster germination.
{{gwi:1303312}}

Obviously they can't continue to grow in such crowded conditions so once sprouted they get their 1st transplant to individual cells in 6 or 9 packs. Transplanted deeply to just below the cotyledons. Very easy to do at this stage. The cell packs are filled with fresh mix with a mild time release fertilizer added. They grow in those until they develop the second set of true leaves. The they get transplanted again, deeply to just below the bottom leaves, to fresh mix in individual containers to grow to garden time.

could I just disturb the plant by taking it out of the cup, and then repotting it back straight into the same cup? Would that disturbance suffice, or do the root systems need to become crampt and then given room to roam?

You could assuming fresh mix and deeper planting. In that big of a cup to begin with it should be easy to do. But no, it isn't that they have to become root bound first for it to work.

since I have to repot some of the ones that have 2 or more plants growing in the same cup, maybe I should keep notes and see what develops.

Excellent idea! ;) And as Trudi said, go with what works for you.

Dave

PS: billtex: There is positively proof seedlings have setback every time you pot up or out.

Exactly, that's the idea. ;) It sets top growth back a bit so that the roots can develop/catch up. End result is a healthier plant rather than a long leggy one that has to be trenched in when planted. As I said above, "If your primary goal is early production then likely stage transplanting would make little if any difference."

I am in zone 6 NY. I use this method:
http://forums2.gardenweb.com/forums/load/strucs/msg0416124122376.html

As of today, most of my plants are blossoming and a few have set fruit already.

I planted my seedlings in ground on 4/01 when they were 28" tall.

dcarch

Dave/Trudi thank you so much.... I really appreciate your having taken the time to really explain things...

I know I'm over thinking things quite a bit, there is just so much to know, and I find it all very fascinating. Thank you again.

Dcarch, very interesting, thanks!

>>That transplanting in itself does not promote an early crop nor an increased yield has been also clearly demonstrated.
So, why would I transplant? Or am I misreading this?I *think* you did misread. I read this with an emphasis on "in itself." The experiment described (in too little detail) after this comment seems to be one in which seedlings were transplanted repeatedly into the same 6-inch pots. So transplanting into successively larger pots is helpful; transplanting in itself, is potentially harmful.

I have typically planted seedlings with very immature root systems. I'm beginning to wonder if it has any connection to my frightful rate of death by fungi and bacteria.

I start my seed in those lil peat plugs..I can hear it now(boo
-hiss) but it works for me...and yes I take off that net before transplanting..I wait till they have at least 2 sets of leaves.., or more and start seeing the roots shoot out from the sides of the pellets..and then put them into a 20 cup..burying them up to the leaves..and then wait till they graduate to the hardening off period and then bam,,in the ground..by that time they several sets of leaves and and as I always have..water them,,,then gently message the cup to loosen root ball and gently put them into their new home...but this time up to the first sets of leaves..roots lookin like they haven't been bound, but wanting to stretch their legs..
I think I posted earlier it was a 3 stage transplant..but actually a 2 step..

I'm hoping to try tomatoes from seed this year (with nursery-grown seedlings as a back-up option!) for the first time, and I just wanted to say that this thread has been incredibly helpful, especially digdirt's post with the photos. I think I 'get' the point of potting up a lot more now!

I had no idea you could pot up at the cotyledon stage, I thought any time prior to true leaf development, any disturbance at all would kill the seedling. I'm keen to give it a go in a few months time when I'm starting my tomato seeds.

If anyone has links to threads or sites that have pictorial timelines of the various potting up stages that would be wonderful. Also, do you guys think that the same technique would work on other tomato-related plants like eggplants & bell peppers?

pepper and eggplants don't shoot roots through the stems as tomatoes do,,I'd say as soon as peppers are at least 4inches tall..harden off for a week and plant them into their new home..the ground..or container..peppers are really hardy.

happy gardening..

the same technique would work on other tomato-related plants like eggplants & bell peppers?

Yes, regardless of the source of the roots, stage transplanting to encourage root development will work on most anything.

Think of all the nursery-produced seedlings you buy to plant - none of them were initially planted in the container you buy them in. They were all transplanted at least once and most twice. They are germinated in seedling flats or plug trays, transplanted to cell packs at least once and often twice, and many are further transplanted to larger cell packs or individual pots. All this before they ever reach your garden at home to be transplanted yet again. ;)

Dave