We started with growing a four-season garden before passive solar greenhouses for year-round growing became popular. Instead, we converted part of an old garage into a food production place and experimented with growing food year-round. Here is an honest 8 years of year-round growing in zone 3 review.
A bit of background information, we are in Alberta, Canada, hardiness zone 3, which means that outside temperature can go down to -40 degrees. We are 51 degrees parallel north, meaning our sun angle is low in winter, and we also have less than 10 hours of daylight from about mid-October to mid-February.
If you have not yet, read the Four Season Greenhouse/Growing Room Review first. A lot of what we write here will make more sense after reading it.
These reviews are not easy to write, we want to be honest and helpful. We know that year-round growing and passive solar greenhouses have gained a lot of popularity, and we know from personal experience how much we wanted to make this work.
With these reviews, we want to be an encouragement for those who have already invested in a year-round growing greenhouse and are looking for tips on how to make it most efficient. But we also want to be realistic and honest to those who are still considering investing in a passive solar greenhouse or year-round growing room.
Note, that all we write here is our personal experience and observations that we have gained over the last 8 years. It is possible that your experience is very different.
And last but not least before we get started I want to mention the “honeymoon” phase. Year-round growing in a cold climate is still very new where the excitement about what is possible overshadows the reality. It is a beautiful phase, and we personally have enjoyed it. However, for someone who is just looking for food security in challenging times, it might not be the right thing.
The beginnings of year-round growing
As soon as the windows were in, and our growing bags ready, we planted heat-loving summer plants. Our first summer was quite successful. We struggled a bit with keeping the grow bags watered, growing in grow bags is a whole other subject.
As the summer season was over, we started our adventure of winter growing in zone 3. Before that, we had already experimented with sprouts, herbs, and microgreens indoors. Since that worked great and is a great way to start, we wanted to see if more was possible.
In January 2015 we learned our first lesson about no growth during the cold and dark winter months. As you see in the picture above in two months, there was no growth worth talking about. That is also where we started to understand the difference between winter harvesting and winter growing. This is important, and we will talk more about it below.
We would have to start plants earlier in order to be able to harvest anything edible during the winter. At this stage, we had no idea how early. Could we still grow heat-loving plants during the summer and then after that greens for winter? We had so much to learn.
A local greenhouse grower shared with us: “Sunshine makes the plants grow and on cloudy days they stand still.” Read more here. It wasn’t also just about dates, the weather played a role too.
When spring finally arrived we had more greens than we could keep up with. Spinach, arugula, and microgreens partly planted in the fall, and partly early in March grew and matured quickly now.
We also finally had a place for seedlings that enjoyed the sunshine at the big windows. And we were ready for more adventures in our four-season growing room.
Especially in those early years of our experience, we were documenting everything. You can find all the garden updates by clicking on “growing” at the top of this blog and all the years for our garden updates will come up. The four-season growing started in ’14.
Winter harvesting vs winter growing
Let’s talk about winter harvesting vs winter growing. Gardeners often confuse these two, and we have done it too.
Winter harvesting is about harvesting cold-hardy fresh greens and vegetables from the garden or greenhouse that grew during the warmer months and are just kept alive and waiting to be harvested during the winter months.
Plants for winter harvesting need to mature before the temperature and light conditions make it impossible to grow more. After that, they just keep dormant for months. It’s a living refrigerator of some sort.
If you want to learn more about winter harvesting, here are some great books:
Inspired by great examples of winter harvesting, we wanted to be able to do that too.
Soon we learned that we also needed to start the plants for winter harvesting a lot earlier than we first assumed. Growing a summer crop, and after that, a winter crop for winter harvesting does not work in our short growing season.
In our first winter garden update, we shared the hard fact that in two months we saw no growth in our indoor garden. At that point, we thought the problem was a lack of light, since all the winter harvesting examples we knew about were much more south, meaning longer daylight.
We still were confusing winter harvesting with winter growing. Puzzled why we were not able to harvest anything. The fact that plants did not grow was very noticeable to us.
It is possible, that winter gardeners in a milder climate, and farther south do not make such a clear-cut distinction between winter harvesting and winter growing. Plants will grow when conditions are right, and under less extreme conditions some growth is always still happening. In our case though, there was non-worth talking about.
Winter harvesting is awesome if real estate for any given plant is cheap. For gardeners in zone 4 and colder, cold frames and simple hoop-house structures will not do it. We need a well-insulated structure (passive solar greenhouse) for winter harvesting. A well-insulated building is not exactly cheap though.
We also learned that we would have to give up on summer crops, at least partially, to have plants ready for winter harvesting. However, if we could get new growth during the winter months, the same growing space would give us more value.
For winter growing to happen, we needed more light and more heat. Read more about winter growing conditions in a greenhouse here.
The importance of the sun’s path
Speaking of light, when building a passive solar greenhouse or growing room like ours, it is important to take into account the angle of the sun. We covered that in our building review. The glazing angle and whether the roof is glazed or not will determine how much sunlight can come into the greenhouse/growing room at any given time of the year.
As growers, however, especially farther away from the equator, we also want to consider the path of the sun. The farther away from the equator you are, the longer the path becomes during the summer months, and consequently shorter during the winter.
Here is the path of the sun in our case. I made the above wheel during my Contour Map Generator training. If you want to know more about your light conditions, we highly recommend it.
As you see in the drawing I made, totally vertical south-facing glazing will catch the winter sun but only a small fraction of the summer sun. Since the summer sun is much higher in the sky, we would need rooftop glazing to implement it, and on the other hand, the lower winter sun can only be captured by front glazing.
In other words, with only front glazing, as is the case with our building, we catch most of the winter sun and very little summer sunshine. Even if our roof was glazed, we still would lose many hours of sunlight due to not enough glazing from the northeast and northwest.
Our growing season is very short, we can catch up on that due to our long sun path, which means many hours of sunlight. We have many sun hours during the short season, in our area 16:33 hours on the longest day. However, a greenhouse or growing room that has glazings only facing south loses that sunlight in the early and late hours of the day.
Since we have a well-insulated greenhouse/growing room facing south, and also a geodesic dome greenhouse, that utilizes the whole sun’s path, we can really see its impact on growth.
We can grow for example tomatoes at both places. In the insulated greenhouse we can start earlier and if choosing indeterminate varieties, grow longer than we are able to in the plastic poly-covered dome greenhouse. However, with a lot more sun hours, we get a much higher harvest in the shorter time in the dome, vs the greenhouse/grow room.
In the dome greenhouse, we usually end the season in late October but have still lots of green tomatoes to harvest that ripen indoors and we enjoy them till the end of the year.
In the indoor garden, tomatoes will produce till the end of the year, those are blossoms that set fruit before daylight hours are too short for that. So there is really no real benefit in keeping the plants longer, even though most years I still do.
Considering the building and running costs, it is way more efficient to grow in a geodesic dome during the summer months.
A passive solar greenhouse does by design not implement the summer sun’s path. The goal here is to have the least heat loss during the winter. Since our growing room has no glazing on the roof, we need less energy to heat it but that also translates into less sunlight during the summer.
Our sun’s path in the winter is very short, the shortest day is 7:54 hours. The angle of the sun is also very low and makes winter the most challenging time of the year to grow anything.
To our knowledge, passive solar greenhouses originated in china, whole landscapes are covered with them. Most of China however is between 30 -45 latitude parallel north. That means that the Chinese deal with a very different sun’s angle and path.
How well a passive solar greenhouse will perform for you, really depends on your location.
Challenges with growing in good soil
Before we talk more about light, let’s dive into the growing medium. A growing room like ours, as well as any well-insulated space, is more like an indoor room than a garden. This is partially true for any greenhouse, but the more air-tight a building is, the more challenging it becomes to still keep living organic soil in it.
The problems might not occur in the first couple of years but after time the lack of a natural environment with rain, wind, and a healthy population of bugs (good and bad), will deplete the soil.
In our case, the room does not have any access to the soil, so we have to bring in a growing medium to grow plants in.
As organic gardeners, growing in compost-rich soil is important to us. At first, we sew grow bags and filled them with Mel’s mix from the Square foot gardening book. It is a great soil mix for square-foot gardening outdoors. In an enclosed environment, things are a bit different.
At first, we faced the challenge to keep the soil moist. Grow bags dry out quickly, and being indoors, they dry out even more.
To help with watering we built a wicking bed instead of the grow bags. That worked much better for watering.
Organic soil is living soil. In an enclosed environment the balance between good and bad bugs can quickly go out of control. In fact, indoors it is best to keep the soil bug free. There is an option to sterilize the soil, and for seed starting, we do recommend that, but then it’s not organic soil any longer.
There is also the notion that soil is free, or maybe just an assumption. That is not so. Even though we did the soil mix ourselves, it was still an investment. To keep that soil fertile, we would need either more nonorganic compost (to avoid bugs), or fertilizers.
Struggling with bugs and aphids we wanted to find a better way.
Water instead of soil
In our eagerness to find a way to grow food year-round, we came across the aeroponic Tower Garden. Aeroponic is known for faster growth, and the tower comes with grow lights. A win-win, so we thought.
Till that time we had never even considered hydroponic and knew nothing about it. But since the tower garden came with everything we needed, it was an easy start. Read a review of the tower garden here.
That’s where we noticed that plants that were directed to the windows grew much better than those at the back of the tower garden with just grow lights. Could we grow without grow lights after all? We had to find out.
We started experimenting with other ways of hydroponic, the Kratky method, high-pressure aeroponic, and NFT Hydroponic. These new methods allowed us to use natural light alongside the windows, vs grow lights.
Grow light vs natural light
For the last couple of years, we have been growing mostly without grow lights just using the sunshine that we get during our cold winters in Alberta.
Growing without grow lights made winter growing a lot less costly. However, we are also more dependent on the weather. Remember the wise words from the experienced greenhouse grower: “Sunshine makes the plants grow and on cloudy days they stand still”.
Winter 21/22 was unusually overcast. Even though we have figured out the heating by now very well, the lack of light really showed a lack of growth. Plants that were planted in summer (early August) grew, but plants that were planted in the fall (late September), did not grow.
Supplementing with light during cloudy and short days is an option. At this point though, we are done with grow lights, we wanted to see how much can we grow with less operational cost.
This brings us to the timing of when to plant the greenhouse in order to get the most out of it.
Planting and harvesting schedule
I wish we could give you a real schedule on when to plant and when to harvest, to get the most out of a four-season garden. But in 8 years we have not come up with one that would be consistent.
What is consistent is the angle and the path of the sun. Since our room has no rooftop glazing, and the sun is high in the sky during the summer months, the room gets the least sunshine from May-August.
Due to the path of the sun, we have less than 10 hours of daylight from about mid-October to mid-February.
If you do the math we really only have about 2 months in the fall and 2 in spring with ideal growing conditions.
Adding glazing to the rooftop would make the summer months more efficient, however as we have said before, not as efficient as a building that is open to the whole circle of the sun (a geodesic dome for example). Having a well-insulated greenhouse for summer growing does not make much sense.
Adding grow lights in the winter would make winter growing more reliable but at a much higher cost.
There is one more small fact, with a huge effect. Aphids and other bugs usually have a life cycle where only eggs overwinter. That gives us a bug-free fall-winter season. Since the room is insulated and in our case heated, the eggs hatch as soon as the daylight gets longer.
Considering all of this we have come up with a more or less consistent schedule for starting the growing season in early August. Some of our favorite fall-winter plants to grow are romaine lettuce, kohlrabi, and Chinese kale. Over the years we have also grown about anything we could think of in our growing room.
Starting some cucumbers in August also works well. They do not have a long lifespan and are done by the time the room temperature drops due to a lack of sunshine.
Starting new seedlings later works in some years, but since cucumbers are super sensitive to cold, they do not always make it. However, a picture of a dying plant doesn’t usually make it into social media. But eh, we wanted to be real in this review.
If we get a sunny winter, we can continue to plant and harvest all winter long. However, if it’s more overcast, plants do not grow. So we often end up with either too many greens or non.
By the time new seedlings for the summer garden join the room, the winter growing season comes to an end. Again, this is very much dependent on the circumstances, some years we have so many aphids to deal with, that cleaning out the old growth only makes sense. In other years if plants are still healthy, we might continue well into spring.
In spring the space is mostly dedicated to seedlings. We also like to bring the fig tree out of dormancy early and grow lemons and limes year-round.
For the last couple of years, we have not been planting a summer garden anymore. Whatever we could grow here between May and August grows so much better outside or in the Geodesic Dome greenhouse.
Is it really worth it?
Every so often the question comes up: Is it really worth it? As you might have already guessed, if our food security would depend on the four-season growing room, it would be a very unreliable source.
Over the years we have shifted our focus from growing food year-round to growing an organic garden during the growing season and preserving as much as we can for the winter months.
We still do some winter growing, because we can, but preserving food makes more sense to us. You can read more about it in our article about where our homegrown food comes from in the winter.
All that being said, we really enjoy having a year-round growing room. However, we do not have the pressure any longer to grow as much as we possibly can.
If we did not have a room like that, we would want to build one again as part of a house, shop, or garage. Any room that is south-facing can be converted into a growing space for seedlings and some micro greens. Don’t forget to add a chair to enjoy the sunshine.
For food production, we would always want to have a greenhouse. We love our geodesic dome, but a simpler structure that lets in all the mid-summer light would do as well.
For people farther south with less extreme weather and light conditions, we would really recommend a passive solar greenhouse. During good years with lots of sunshine, we can glimpse the benefits of having one.
Feel free to share your experience or questions about year-round food growing in a cold climate.