Photoperiodism is a technical way to explain light and dark cycles. Anyone who’s spent any time here in the north understands that we get a LOT of light in the summer. The sun simply doesn’t set for months on end. This is great for some types of plants, but not all plants can deal with the extended light well.
The issue is that many plants have genes that use light cycles to decide when it’s time to flower. This works great in the lower 48, where these typical light cycles will tell the plant when fall is approaching and it’s time to start flowering. Up here, that midnight sun can trigger the flowering response way too early – even early summer – to the point where it’s hard to get much of a harvest. The plant will typically send up flowing stalks extremely early, or start to show flower growth in the case of herbs.
The plants we’ve consistently had problems with early flowering include:
- Spinach – Even slow to bolt varieties
- Summer Savory
- Boc Choy
The herbs mentioned above are understandable. There are not vast varieties of most herbs, at best you might have two or three types that you can try. These have long been grown in areas that don’t experience our extreme photoperiodism and so it’s understandable they could have problems dealing with so much light. Many of our herbs come from latitudes in the 40’s, growing them at 65 degrees north might as well be a different planet.
With spinach, though, we’ve spent a lot of efforts trying to get these to grow without early flowering. We’ve tried the varieties that are known to be “slow to bolt” and are less sensitive to photoperiodism. Even these show early flowering issues. In 2016, we got our spinach in the ground early enough to get one, perhaps two, harvests. After that, though, we couldn’t get spinach to grow without flowering within a couple of weeks, well before they were mature. This year, we didn’t get spinach in the ground until late May and unfortunately, all of our plants have started to bolt within weeks. That said, you can plant spinach in both the early season (late May) and the late season (mid-August) and get a harvest or two.
Bok choy does seem to grow really well here, but will quickly go from a nice plant to flowering-ready in a matter of a day or two. We haven’t observed that this negatively affects the taste, we simply cut the flower stalk and harvest as soon as possible. It would be great to get this fast growing plant to deal with succession planting, but by July, they will put all their energy into flowering as opposed to growing larger.
We love growing cilantro, it’s a basic staple in our garden. Thus we’ve put a lot of effort into finding a variety that resists early bolting. Practically every variety out there bolts extremely early, except for one. Calypso cilantro is a slow to bolt variety that does what it says. We’ve found it resistant to bolting, almost to the point where it’s impossible to get coriander – the seeds of cilantro. Calypso is the only variety of cilantro that we grow anymore unless we’re specifically trying to produce coriander.
I’m sure there’s a few more plants out there that we haven’t tried to grow that would have these problems, but otherwise, we haven’t had issues. Many herbs like thyme, sage and mint will hold out into July and begin their flowering processes slightly later in the season. Many of your larger cool climate crops, like broccoli, will start to flower at the right time when you’re also ready to harvest.
As for herbs, we’ve countered the northern challenge with quantity of plants. Sure, we might not be harvesting monster oregano plants. But, if we harvest a half dozen smaller plants in early July, we still can get plenty to last us through the year. We end up drying most of our herbs as this preservation technique is the most useful to us. For everything else, we just enjoy the brief seasonality and any harvest is particularly special.
One thing we will be doing this year, though, is trying to bring some of our gardening indoors. We are very interested in having access to fresh food year round. Indoor growing allows us to control the elements more precisely, so we can easily induce a period of darkness that the plants need. There is little doubt we will be looking at growing some of the plants that have given us the most challenges!
Growing vegetables up north here is not without its challenges. This one is unavoidable, it’s just how things are this far north. Sometimes you just have to deal with it and go with what grows.