tedln
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Growing onion seedlings in trays under lights.

I've always purchased onion seedlings in January and planted them in mid January for spring/summer onion bulbs. This year, I want to plant onion seed densely in trays under lights to produce small seedlings for mid January planting in the garden.

How deep should the soil media be in the tray?
What is a good soil media for growing onion seedlings?
What is the typical time required to grow from seed to transpantable seedlings?
How densely should I plant the seed to produce 1/4" thick seedlings?
Should the newly germinated seedlings receive any fertilizer?

Ted

TWC015
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Joined: Sat Mar 27, 2010 8:43 am
Location: Jefferson Co., Arkansas

I'm trying onions from seed inside this year as well.

I just started some onions from seed. I sowed most of them on September 25. Right now mine have 2 leaves and a third should be visible soon. I sowed mine in an 18-cell flat with 8 plants in each cell. The soil mix is regular Miracle Gro, the same I use for all plants.

I plant to set my plants out in the ground around late November to let them overwinter outside. They probably won't be the 1/4 inch thickness as the plants I've bought, but I don't want them that thick since I will put them outside before winter.

I'll probably start a few more onions from seed in early December and plant in early February just in case these bolt from winter.

garden5
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Location: ohio

I did for the first time last year.

I used mainly dirt, amended with a little compost and screened. I then took it and put in one of those 72 cell propagation trays (each cell was about 2 in deep).

Next I sowed 3 seeds to a cell, and only sowed them about 1/4 in deep. That's as deep as is usually recommended to sow them. They were planted the beginning of February.

I lost a lot from a low germination rate and from damping-off. I recommend watering them with some chamomile tea every once-in-a-while to help prevent this (it's a natural anti-fungal).

I grew them like this, without any fertilizer (in hindsight, some fish-emulsion probably wouldn't have hurt) and without grow lights. I kept them in front of a window and had a shield of aluminum foil behind them to help keep them from pulling towards the window. Lights would have been much better, but I didn't have any more room under them.

Also, I cut the tops back to about 3 or 4 in. whenever they got long (this helps promote stockier sets).

I planted them at the end of April, at which point in time they were about 1/8 in. in diameter and about 4 in. tall......the store-bought sets dwarfed them.

As the season progressed, very few were lost to the elements. Despite their small size, about 1/3 of them produced good size bulbs 3 1/2 to 4 in. across, 2/3 of them produced small/average size bulbs 2-3 in. in diameter, and one didn't do anything. The soil they were growing in was also marginal at best with lower organic matter

All in all, I think if you start 2 1/2 to 3 months before you plant out, sow a good amount of seeds (but not so much that they are unbearably crowded), keep them under lights, give them a light fertilization periodically, and grow in good soil, you will be enjoying some nice onions next year.

Oh, and if you use lights, there is a certain time-frame to give the onions light and to give them darkness. This is done because onions are light-sensitive and will go into production too early if they get the wrong amount of light and darkness each day.

I'm not too familiar with this system, but I believe it's less than 16 hrs/da for long-day onions. I think you grow short-day, which I have no experience with given my location.

Gix did this as well, this year, so hopefully he will lend some of his experience as well. Oh, and there are some members on here (Applestar?) who know more about night/day cycles of the lights, too. It's not as hard as I make it seem :lol:.

I hope all this helps you out. Good luck :D

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gixxerific
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I used a plastic to-go bottom. I just threw the seeds in there like grass, and well they came up like grass very thick. I may try to start them in individual cells this year. I also started them later about the time G5 did. We talked back and forth this spring seeing how each others onions were doing. Jan might be good for me maybe late Dec. The soil I used was a homemade mix of compost, potting soil and humus etc. They didn't as well as G5's but they did produce some small bulbs.

Good luck.

As far as the lighting periods for onions I'm not sure it matters as much when seedlings. But the photo-period length determines when they will start to form the bulb. There is a ton of info on the web.

garden5
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Location: ohio

Another thing I should mention is even if you grow your own onions from seed, you should still purchase some back-ups from the store.

Gix and I both did and I think we're both glad we did. I don't know about Gix, but my store-bough ones did overall better than my home-grown ones.

That's not to say it's not worth it to grow your own from seed. It worked for me, I just have to refine it more to work better :wink:.



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