Planting For Fall Harvest?

If you plant onions now, they’ll start bulbing (pushing away the surrounding soil) very soon, even though the onions have not fully developed. This is because bulbing is triggered not by plant size, but by daylength.

Spring planting allows time for the onions to grow and mature before days are long enough to start the bulbing process. Late summer planting simply doesn’t provide the proper conditions for onion plants to grow before bulbing┬ábegins.

bolting onion plants

Overwintering Onions

An alternative that is by no means guaranteed is to plant in the fall, when days are short enough that bulbing will not occur, with the intention of harvesting the onions the following spring. This process, called overwintering, poses two risks.

One possibility is that the onion plant will not develop much before cold weather sets in. Tender young plants are not likely to survive frigid winter temperatures.

If the plants do make it through the winter, in spring they will be prone to start flowering, a process known as bolting. Bolting results in decreased bulb size, shorter storage time, and the possibility of decay. When an onion bolts, a hardened stem shoots from the plant producing a flower pod at the top. This is called a “seed stem” as there are onion seeds in the flower.

While overwintering onions requires Mother Nature’s full cooperation, you’ll end up with extra large onions if you’re successful.

Green Onions

If green onions are your objective, you can plant long day varieties that require at least 14 hours of daylength. Here in South Texas, we can only grow extremely long day varieties in the early fall because other varieties start bulbing just two weeks after we plant. 

Your Best Bet

If you want to enjoy home-grown onions for as much of the year as possible, your very best bet is to grow plenty of storage varieties in the spring. Planting when conditions are ideal is far safer, and we offer plenty of varieties that store well for many months of enjoyment.