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onions from seed

Posted by veggiecanner Id 04 (My Page) on
Tue, Dec 12, 06 at 1:55

I have grown onion from seed for 4 years now. But I need some advise on how to get larger transplants. I start them late january/ early february under shop lights. i use starting mix and water with blue fertilier at half strenth.
I need to know about how deep the soil should be. I am starting to think the 6-pk cells are just not deep enough.
I start Walla Walla, white and yellow spanish and a red type. But would like to get more than hair sized plants to plant in April.

Follow-Up Postings:

RE: onions from seed

It sounds like the shop light is to far away from the slips. With fluorescent lights you have to keep them 1 inch from the plants until they reach the desired height.

RE: onions from seed

I start my seeds in late Feb (seems you are starting them too early to me but I don't think that is your problem) also growing them under 4' shop lights. I use 4" X 6" squares (tried cells and I prefer the 4 X 6 containers) and drop a seed about every 1/4" getting 5 or 6 rows per 4 X 6 container. Tight spacing when seeding containers does not seem to cause small plants at transplant time. Ever see commercial onion plants? They are so jammed together you would think it would adversely effect them but they are quite tall and have large tubes.

I agree with the other poster, I think the light that the plants are receiving is too weak because it is too far from the plants. Use regular shop lights nothing fancy. You have to (MUST) keep the lights no more than 2" above the tops of the plants for 16 hours per day, even 1 1/2" is good but higher than 2" is not correct for seedlings - onions, whatever. I water them when dry but only fertilize 1 or 2 times at the most with dilute organic fertilizer. The lights are hot at this close proximity so even in a cool 50-55 degree basement the onion plants dry out fast especially when small so be sure to look at them every day. I have to cut them back several times when they get 4-5" tall. I think/believe that letting them grow tall also creates a larger tube. If you cut them say at 3" tall back to 1" that may (not sure) create smaller diameter tubes, like hair. I cut them back to say 3" tall. By April 20 they are ready to go out based upon outside temps. The tubes may be large or smallish but they grow fine. The depth of the container seems to not matter based upon my results over the past several years. The roots just grow together in a 1 to 1 1/4" deep 4 X 6. When transplanting, I just gently pull the plants' root systems apart, poke my finer in the soil and swirl the root system into that hole and back fill it.

I think the spacing of the plants when transplanting is important. When I spaced Copa, Mars and other normal sized onions at just 2 or 3" on center the bulbs were small. I now space them 4" on center and the bulbs grow much bigger. I strongly recommend 4" spacing and if you have lots of room use 6", it can't hurt, tho onions will grow to their normal size and not just get bigger and bigger cause they have extra room. For large onions like Aslisa Craig, I use 6" spacing and again if you have the room to waste 8 or 10" would be better.


RE: onions from seed

Are you trimming the seedlings?

I'd gotten into the habit of giving them a haircut to keep them at 4" height. This prevents them from flopping over. But I noticed that it also produces thicker "stems".

Like the others, though, I don't give much thought to the thickness. A hair-like seedling and one as thick as a pencil both grow about the same once transplanted.

Rather than cells I merely broadcast seed in small containers; the kind that mushrooms come in at the market. Spacing seems to be totally unimportant. These containers, btw, are the same depth as a cell pack. So I don't think soil depth is your problem.

I remember an old Victory Garden episode where he recommended using egg cartons, planting one seed in each cup. Yeah, right. I've got lot's better things to do than plant onion seeds one at a time. But the point would be that they have no soil depth to speak of, but grew seedlings just fine.

>seems you are starting them too early to me<

I don't think so, Tom. He's allowing 10-12 weeks from seed to transplant, which it perfectly fine. I set seed the beginning of January, for a mid-March transplant, which is about the same timing as his.

RE: onions from seed

i used to start my seeds on 2/22 (all 2's was easy to remember) but i shifted to 3/1. i assumed (!) the longer growing maybe be detrimental (8 days is not a difference i'm referring to a full 30-45 days earlier), kinda like 'root bound' cabbages that sit too long, they do lose their green color and get a tad yellow but recover just fine once put out. perhaps i should start mine in early feb? i'd like larger transplants (larger tubes are easier to work with) but since bulb formation is triggered by the mid june day length i figured it did not matter.

====> he recommended using egg cartons, planting one seed in each cup

what! i'd need approx 40 egg cartons! what a waste of space! i did an experiment one year. in 1 container i did the usual row planting and spacing (4 x 6 container with 5-6 rows with 12-14 seeds per row) vs another container where i just broadcast them. the former takes a while to seed using tweezers vs 5 seconds for the latter! the germination was a definately better in the row planted container tho the other container's seeds, once sprouted, grew ok. since seeds are good for 1 year (onions will germinate in a 2nd year but at a lower rate so i just buy new seed each year) i probably should just plant all of them in 30 seconds but i have to admit i do like planting the seeds 1 at a time in rows.


RE: onions from seed

Hi Veggiecanner,
I start my onion seed in either January or February, and have noticed little difference in how they come out.
I use those styro mushroom containers filled with soiless mix that is about 3/4 full. I plant in rows in these containers using the side of a Popsicle stick to make an impression, then sow them quite close together - it doesn't seem to matter either! They grow in quite thickly, always look kind of measly - but turn out just great. I keep them so close to the fluorescent light that they almost or do touch. I also give them haircuts at around 4", since many can be very different in height on their own. I never feed them in this seedling state even thos i do not use soil. A few times, i have put an inch of real pottig soil in the containers topped by fluffy soiless mix - then the roots grow downward and find a bit of nutrition to carry them thru to transplant time. That may help, but i have only done that twice. When i take them out to plant in April, i just pull them apart and space about 4" at least. It really never fails using this method.
Good Luck!
Glad- zone 6a

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