Trimming onion seedlings

gjcore(zone 5 Aurora Co)March 4, 2013

I notice a lot of people recommend trimming onion top seedlings. I planted two flats about 3 weeks ago one NY Early and the other Red Bulb. Right now the tallest ones are about 7 inches. Not sure how much taller they will get indoors but it doesn't seem they are bothered by growing into the lamps or falling over a bit.. The bulbs are old school T12 cool whites and also 2 40 watt CFLs.

I've read people's opinions saying that trimming promotes stronger roots and thicker stems but have yet to find a single incident of anyone doing a side by side study.

How necessary is trimming onions? And what is the science behind it?


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To sum up lots of mentions in various threads, it seems that those of us who start early and must keep onion seedlings under lights for months favor trimming. Those who have lots of natural light to work with, either from a nice climate or a greenhouse, often favor not trimming.

I am among the trimmers, mostly to keep the January-sown plants manageable and upright, and to increase light penetration to new leaves. In the next couple of weeks, when I can put the onions outside at least a little bit, they will stiffen up nicely and I'll stop trimming.

    Bookmark   March 5, 2013 at 12:35PM
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I too trim. It's still a bit too early for them to go into the ground here in Vermont plus they are absolutely delicious in salads and other foods. I've not run side-by-side studies to determine the size of the bulbs but they sure get leggy if I don't trim them.

    Bookmark   March 10, 2013 at 6:33AM
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