As you can see in the picture, the seedlings were about 1" on March 10 - so 7 weeks old.from sprout. They are a mix of better boy, farm stand, super 100, and best boy.

I upgraded to T5 lights this year, and am using a new mix of supplements and nutrients. It seems to be paying off :)

Anyone have any tips for hardening off bigger plants? I assume the normal approach - but would appreciate any input.

You’re pretty lucky to have such tall seedlings. You could use the Trench Planting - L shape method: 1 ft. horizontal - for more roots - and at least 1 ft. vertical - to avoid splashing on leaves. Mulching - straw bail…- is always a good idea.

But transplanting at that size is going to require extra work and care - much deeper holes or deep trenching and stripping off all the lower branches first - so I assume you know that transplants that size aren't really desirable?

Dave

Is the only downside the extra care - or are there other factors. I always plant my seedlings deep, etc, So do taller transplants lead to more problems overall - or just some more care? What is the ideal size, and why? Thanks again!

I have T5 lights too, and my tomatoes grow very fast. I'd have to plant out at 4 weeks to have seedlings under a foot tall. So I'm used to big plants. They do seem to produce fruit a couple weeks earlier than the tiny plants my neighbor gets from the big box store and plants at the same time.

The ideal size for a transplant is 6-8", maybe 10" tops depending on the inter-node length.

Much beyond that they are much more prone to breaking, more difficult to support adequately, more prone to wind damage, and most importantly, more transplant shock. Thus they tend to take longer to recover from transplanting than smaller transplants do. Their root development has often been retarded so is insufficient to support all the top growth. That means it takes the root development needed that is triggered by transplanting longer to catch up. The result is a stressed plant that has to be monitored carefully.

Plus if they are so large that they have already kicked into boom mode those blooms have to be removed to put them back into growth mode.

Trench planting horizontally so that only the very top set of leaves is left above ground will lessen the problems. It brings the top growth and root development back into a sort of balance and lots of new roots will develop all along that buried stem as well.

Many folks seem to feel that the bigger the plant when they buy and/or plant it the sooner they will get tomatoes. But research shows that just the opposite is true. Smaller, less stressed transplants will always catch up quickly and surpass the bigger stressed plants in long term health and production.

Dave

Everyone seems to want to rush the season. Not sure why when the price one pays can be very high.

Dave

Being in zone 5b, I suggest you to repot. It will be a while until transplanting, and by then, the roots will be too crowded in the 4’’ pot. I suggest you to use these CowPots - 6".

>Is it too early to start hardening off?

I think it’s too early.

>Some of my seedlings are about 2", some smaller.

They are way too small to harden off, imo. I think they should be at least 5-6'' high.

I would have to disagree with using the cow pots, or any of the fiber-type pots, however. Far too many issues with them to suit me. if you do use them please be sure to strip off all the pot prior to transplanting them.

Dave

Can you elaborate on that? Will a hardened off seedling not continue to do well if brought back inside? I've been taking my seedlings outside on warm days, thinking I was helping them along. Is that a mistake? I'm still 2-3 weeks out from planting.

Dave replied: > Can't really say without seeing them but if they are only 2" tall and smaller then 4" pots should be fine IMO.

The reason why I suggested repotting is because Sharonie - being in Montreal, Canada (5b) - will probably transplant her seedlings in about 1 month from now. In one month, imho, a 2’’ seedling will grow pretty tall, with crowded roots in that small 4'' pot. I don’t know what kind of pots Sharonie is using: if she uses plastic pots, the roots will be contorsionated in the 4’’ pot. If she uses cowpots, the roots will penetrate the pot’s wall, and that is not a big problem.

Dave wrote: > I would have to disagree with using the cow pots, or any of the fiber-type pots, however. Far too many issues with them to suit me.

Can you share with us those issues? I used cowpots for the last 2 years and everything was fine, no issues whatsoever.

I really believe what I see in this picture where they compare two plants in two different types of pots: plastic and cowpots. I like the plant in the cowpot.

Dave wrote: > if you do use them please be sure to strip off all the pot prior to transplanting them.

While some say, it's ok NOT to strip off the pot, I always did and I mixed the pot with the soil where I planted my tomatoes. It’s cow poop, a fertilizer after all.

Sure. Taking young plants out for an hour or so to get some sun and fresh air is one thing. Is it necessary? No. Is it beneficial? Maybe, if done very carefully. Can it be risky? Yes. But that is not hardening off.

The process of hardening off is done to permanently adapt the plants to the totally new and different environment they will now be living in. Take them in and out and in and out over long periods of time and they never adapt because the environment is constantly changing.

Think of it as moving. You bought a new house, go through the process of gradually moving all your stuff to it a little at a time, and 1/2 way live in both houses for a week or so with all those frustrations. Finally you settle in to the new house. Are you then going to go back to the old house to live when everything is over at the new house? Nope, once you are moved, you are moved, right?

So when it is getting close to planting time they need to adapt to that environment. Gradually they go out into it, learn to live in their new house. Now if you take them back to the old house for any length of time after they have adapted to the new one, they have to re-adapt all over again and again.

Make sense?

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Daniel - if she needs to repot later on that is fine but she sure doesn't need to do it now. And a 2" seedling would be over-whelmed in a 6" pot.

And how much growth the plant has in 1 month all depends on the growing conditions provided. If they are given the proper cool growing conditions with plenty of light then a 4" pot will be fine for a month and the plants will be approx. 7-8". Will it be rootbound? Possibly but plants can survive just fine for a brief period until they can be planted.

If they are exceptionally warm conditions with not enough light then yeah they will be taller and lanky. But even transplanting to a larger pot won't prevent that from happening.

If you are happy with cow fiber pots that's fine but I have tried them and been sorely disappointed. The issues associated with using them are well documented and have been discussed here may, many times. The search will pull up all sorts of discussions about them as well as Jiffy pots, many with pics of the problems.

They do not compost in the soil unless you have lots of clay that will retain water for a long time around them. Folks have posted pics of them in the soil a year later.

Roots do not penetrate them as advertised unless the pots are kept overly wet. Folks have posted pictures of pulling up plants with the pot still intact and filled with roots but none outside the pot.

To keep the pots wet enough that means the plants have to be kept overly wet since the pots pull the water right out of the soil. That leads to root rot and stunted plants, yellowing leaves, fungus gnats, etc.

It's your choice but IMO plastic pots will always outperform any of the fiber pots. If one wants truly direct planted pots of some kind use newspaper pots.

Dave

Make sense?

It does. I've often wondered if plants spending time outdoors get (for lack of a better word) "tanned", such that they don't photosynthesize as well when they come back inside. If that's true, then it would make sense that it would take some time for plants to get used to the indoors again.