Over the past couple of years, we have done some work looking at overwintering onions here in New Hampshire. We found that some varieties of onions could be seeded in August or September, transplanted in the field, covered with low tunnels, and harvested as beautiful bulbed onions in May and very early June. (You can read about that here). We think that this has some potential throughout the state, since it worked well in North Haverhill as well as down in the banana belt (Durham).
There are some challenges, of course. For one, we have yet to find red varieties that perform as nicely as the yellow ones. Second, low tunnels are a bit finicky to manage (you can read more about that here). Lastly, it seems as though it may be difficult to get the planting dates exactly right – too early and you end up with bolted onions, and too late, and the onions don’t size up well.
Because we know that variety and planting date are very important factors, we set up what we think will be a very interesting and informative experiment. Right now, we have eighteen varieties of onions that were transplanted at 6 different dates throughout the fall, in low tunnels as well as a high tunnel. Things are looking good out there!
Varieties include several red ones, short-, intermediate- and long-day types, and one sold as sets (rather than seeds). Stay tuned – we should have some very interesting results as spring rolls around!