Dense planting and root bound before true leaves
 

This was my first year trying the dense planting method, using 50 cell trays and a 50/50 mix of Coir/Coarse Perlite. I started my seeds on April 2nd.

I was curious to if anyone has ever encountered their seedlings to go rootbound in their densely planted trays, before their first set of true leaves are fully developed. That is the situation I'm faced with. I got 2 to 3 inch seedlings, with some seedlings not even showing true leaves yet. Some have visible true leaves but they are puny. A further investigation of the soil shows the roots filling up the cell and starting to come out of the drain holes.

As before mentioned I was using a 50/50 mix of Coir/Coarse Perlite (no nutrients added, but have watered with Actinovate once), watering maybe once a week (allowed the soil to dry out), 1020 trays on heat mats with soil temps ~75-80 F. Using artificial lighting (over driven T8 ballasts with 3000K and 6500K bulbs) for 16 on 8 off.

I have transitioned the plants outside and try to get them out there as much as I can, depending on the weather and if I'm going to be around to bring them in.

I also notice some yellowing on the seedlings in blotches, kinda like a spray paint like pattern. Not sure what the cause of this is, I'm going to attach some images:

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*One of the seedlings has brown tips and yellowing, though others don't*

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I'm going to start potting them up into 16 oz cups and hope for the best. The only thing I did different this year was the dense planting and the usage of heat mats because I had problems germinating peppers last season in my cool basement. I hope somebody knows what I did wrong :O.

Yes, you have to tear the roots apart when you repot. It's not a big deal. But roots growing out of the bottom is usually due to moisture under the pots and seedlings will do that as soon as they have a chance.

Not a problem at all. the point is not to save all of the roots - it is to ease the plants apart with some of their roots and reward them with their own living space! I did that to 6000 seedlings this year (some were at 50 seedlings per cell)...and lost none! I've often been a bit rough and ended up with one with no roots. No worry - plant them deep in damp mix, and leave under the grow lights until it roots, which happens pretty quick.

Thanks for the replies guys. I'm not worried about tearing or losing roots. I'm worried about the lack of true leaf growth or top growth. The years prior my seedlings were greener, and put out true leaves before I had to pot them up. This year they seem stunted and I was wondering if its because they have become root bound? Or maybe its something else. Either way I'm in the process of repotting them and so far got about 50 done.

[quote=nctomatoman;166682]Not a problem at all. the point is not to save all of the roots - it is to ease the plants apart with some of their roots and reward them with their own living space! I did that to 6000 seedlings this year (some were at 50 seedlings per cell)...and lost none! I've often been a bit rough and ended up with one with no roots. No worry - plant them deep in damp mix, and leave under the grow lights until it roots, which happens pretty quick.[/quote]

I've snapped seedlings before and simply stuck them rootless into soil up to the cots, they've survived. Tougher things than we give them credit for.

I would say that lack of nutrients had alot to do with the slow growth. also, the 3000K lights are not helping as much as all 65000K

It was my thought that the seedlings could grow true leaves without nutrients? I've always used the combo of 3500 and 6500, but you've had better luck with just the blue spectrum?

I bought some composted chicken manure last year that's still sitting in a bag. I'm going to make a tea out of it and dilute water them with it.

Red light is mainly needed to induce flowering, and the 6500K bulbs have comparable amounts of red to the lower temp tubes, they just have more blue, so more of your electricity is getting to the plants.


I have not tried to grow seeds in straight sand so I don't know how far development will go on just water, but I have dense planted in low nutrient mix (which said it has starter nutrients in it) and had plants stall with very small first leaves. Coir is often rinsed repeatedly to get rid of sodium so chances are good that it doesn't have much in the way of residual nutrients. I would go with a balanced fertilizer rather than the chicken manure, which will be high nitrogen, low P,K.