Well, we didn’t exactly scream from the mountain tops that we were conducting a basil trial this season, but we did briefly mention it earlier this season.
We were seriously looking at basil production outdoors in subarctic climates and comparing it directly against the relatively well protected environment of a climate controlled greenhouse. The results are in and we can talk about what we’ve learned.
For a long time, we’ve known that outdoor production of basil is possible, even at subarctic latitudes. We were doing it in our earliest days of growing here. But, it didn’t do great. Basil benefits from soil warming techniques like raised beds and container gardening. But, it’s also one of those plants that we know benefits from warmer ambient air temperatures. So, once we had built our greenhouse, it was one of the very first plants promoted into growing in our greenhouse.
At the same time, we’ve been evolving our container gardening techniques quite significantly. We felt we were finally at the point where we could provide greenhouse and outdoor grown basil a “fair shake” and offer a decent comparison between both outdoor and greenhouse grown basil. So, exactly that happened this year. Our sub irrigated container gardening technique is perfect for a plant like basil that can benefit from constant access to water and nutrients.
As often happens in our trials, we aren’t conducting “science grade” studies. The biggest flaw in our “study” is that we’re growing different types of basil outdoors than we are in the greenhouse. But, we do try to control enough variables, like growing technique in this case, that we get a sense of truth. Honestly, that’s good enough for us and it helps inform our well developed instinct when it comes to growing.
Our early season performance was neck and neck. Honestly you could barely tell a difference between outdoor versus greenhouse grown basil. But, as we approach our “final harvest” time of basil, the differences are becoming more and more obvious. Our outdoor grown basil is succumbing heavily to the realities of outdoor growing in the subarctic. Sure, we’ve had our warm days that are perfect for a plant like basil, but we’ve also had “record levels” of cold and wet.
While we can expect differences in leaf size among basil varieties, it’s fairly obvious that our greenhouse grown basil is a clear winner here. We’re also seeing a lot more nutrient deficiency in our outdoor grown plants, on account of nutrition being washed away by heavy, seasonal rains. The cold stress on our outdoor plants is fairly obvious, despite having the warmest soil temperatures we can achieve. Curiously, our outdoor basil also flowered earlier and with more vigor, an indication that our plant is more focused on reproduction than it is “loving life.”
I think had we been focused on a very early season harvest of our basil, there would be very little benefit to outdoor versus greenhouse grown. But, if you’re looking to maximize your “cut and come again” trips to your basil plants, that also help them grow more healthy, it’s very clear that the warmer ambient air temperatures of a greenhouse provide maximum benefit.
We were hopeful that we could kick our basil out of our greenhouse, but for our production goals, this doesn’t look like it’ll be a reality. Outdoor grown might actually work for some of you, though, especially if your primary objective is to grow enough to preserve. If you don’t need or want that late season August harvest of massive, bifurcated basil plants, then you can definitely ride those early heat waves in July and call it a day!
We may do this again, perhaps with different varieties, but we suspect the results would be similar, if not identical. Sure, those super warm seasons are going to just be winners all the way around. But, that’s not our “average” season and we try to grow into that average, which helps us win when there’s any kind of seasonal difference.
