The Q&A Archives: Starting Onion Seed Indoors

Question: I start my onion seed in potting soil under lights. I use two 40 watt flourescent bulbs and planted the seeds about 10 weeks before planting time, but the plants do not fill out like they should. They grow fast enough because I have to trim the tops back 2 or 3 times but they are spindly. Last year I planted them in the garden and none of the bulbs got any larger than a quarter. Can you give me any suggestiopns to give me healthier plants?

Answer: When you are starting any plants from seed, they require the right conditions. It's best to use a commercial sterile, soil-less seed starting mix, and make sure that you keep the soil is kept moist but not soggy. Most seedlings will grow best at temperatures between 60 to 70 degrees F.

Onions are unusual, in that they are day-length sensitive. There are short-day and long-day onions, and you need to choose the right varieties for your region. Since you are in the north, in Wisconsin, you should choose long-day varieties. Short-day varieties will not form bulbs properly in your region.

Onions can take up to 120 days to reach maturity when planted from seed. You may want to grow onions from sets instead, since they will mature much faster.

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