This week I get to introduce you to another fixture of the aquaponic world - Vlad Jovanovic from Serbia. Known as the Aquaponic Alchemist, over the years Vlad helped myself and many others with our questions about biochemistry, plant pathology, water chemistry, and dozens of other topics. This week he shares with us about his experiences growing in a cold climate. You can also find him at his Kansas-based store Atria Aqua Gardens. Enjoy!
If you are reading this, chances are you’re not gardening in Barbados. Everyone here is probably very familiar, and thankful for Frosty Fish/Jeremiah’s insights on things like heat retention, insulation, along with other smart ways to help protect your aquaponic system from the menacing threat of the freezing cold. Gardening of any sort during the winter can certainly be a challenge, and we who live in Northern climes would do well to take his tips and tricks and good advice to heart.
What I’d like to do now though, is present some other, hopefully more positive aspects that this frore and frigid phenomena called winter may bring to our gardens, aquaponic or otherwise.
Hopefully everyone reading this has by now given up on the fanciful idea that they will be able to grow and harvest tomatoes and peppers in February…in a hoop house…outside…in sub-freezing temperatures…without breaking the bank. As the mercury falls, we’ve relegated our horticultural en devours to the realm of rutabagas, collards, Swiss chard, and other cold tolerant crops.
Frost Tolerant Plants
So what is it exactly that makes one plant frost/freeze tolerant, while others turn to mush at the slightest bite of frost? Well, here’s a hint: Have you ever tasted a carrot or rutabaga that was grown in warm weather? The taste is not exactly inspiring is it? Bland and rather flavorless (or bland and very woody in the case of the rutabaga). Carrots, parsnips, rutabagas, Asian greens, collards, turnips, beets, brassicas, etc… grown in cold weather taste fabulous. They’re full of sweetness (hint, hint) and turgidity.
Part of what makes a frost tolerant plant able to do well despite the cold, is that they have developed the ability to convert portions of their carbohydrate stores into simple sugars. This accumulation of simple sugars helps protect their tissue from freeze damage. Though this isn’t the only mechanism at play, but it’s one of the major ones (and it’s the mechanism most favored by my taste buds). In the growing industry this is called “chill sweetening”. The taste of my Bok Choi and lettuces grown in the Spring/Summer can’t hold a candle to their winter grown counterparts.
Turnips grown in the cold taste crunchy and sweet, and tend to lose most all of that spiciness that kids don’t seem to enjoy. I know a certain 10 year old who thought that she didn’t like tomatoes. It turns out that all she had ever tasted were of the bland, store bought, grown out of season variety. Her thinking changed when she tried a fresh homegrown one…grown in it’s proper season. Same with turnips, beets, parsnips, etc…Many of us have only tried growing (and eating) these things in the Spring, out of their true season. Sure, they’ll grow just fine then, but they also certainly lack the flavor that chill sweetening brings them.
As temps begin to get fall, frost tolerant plants also begin to produce anti-freeze proteins (believe it or not, that actually is the scientific term for it). They begin to alter the composition and structure of their cell membranes to be able to withstand the deleterious effects that the freezing cold would normally have on things like cell wall structures. Alterations in leaf polar lipids, starch, sugar, fatty acids, polypeptides, soluble proteins, all contribute to their enhanced ability to withstand the otherwise inhospitable winter and below freezing temperatures. Some of these biochemical changes and alterations in physiology take some time for the plant to employ. So really drastic, quick plunges in temperature will sometimes damage even the most cold tolerant of crops (especially if accompanied by low humidity). If the decline in temps is somewhat gradual however, cold tolerant plants have time to kick these various freeze protection mechanisms into gear.
Humidity and the Cold
Something that a cold weather aquaponic greenhouse already has going for it, is it’s environment of high humidity. While high humidity and low-ish temps do tend to breed certain fungal pathogens (especially if you don’t vent at all during the day); high humidity is somewhat desirable in the winter time. This is because it’s not the freezing temperatures per say that damage cold tolerant crops, but desiccation. Since the cold weather crops have moved much of the water out of their cells to keep from freezing (re-crystallization of water molecules) the cold, dry winter air simply dehydrates them. That’s why frost damage in a cold tolerant plant looks like a scorching or drying. While the freeze damage to non-frost tolerant plants tends to manifest in the form of “mushiness”, and not dried out scorching (desiccation). Again, this damage to otherwise frost tolerant crops generally only happens when temps fall quickly and are accompanied by low relative humidity.
Most of our aquaponic greenhouses are anything but dry in the winter time. At times, walking into my 2,100 sq.ft AP greenhouse, is like walking into a cloud. Especially in the early mornings after cold Winter nights, or anytime the air temperature inside the greenhouse is less than my water temperature. All of the cold surfaces get foggy and moist with condensation. As painful as it might be, you need to open the doors and vents and invite some of that cold dry air inside, to take care of some of that moisture. If you don’t, you run the risk of things getting out of hand with pathogens.
Heating for Dehumidification
Heating the air at night also helps to keep things from getting too moist. My home built pyrolytic gassifier stove helped keep things tolerable on brutally cold Winter nights. It’s pretty much a “Rocket” stove on steroids built out of old, super thick walled East German and Jugoslav army barrels and some scrap metal.
It’s not your typical double barrel stove, though it may look like one from the outside. Inside, it’s a different beast entirely. I wanted “rocket stove” type efficiency, but didn’t want to have to feed the ‘classic’ rocket heater “chintzy little splints” of wood every 30 to 45 minutes. I needed something that I could load up and forget about until morning. I built it and started using it a few years ago. Jim Fisk provided the basic design, I just tweaked and suped it up a bit. It works like a charm, and I must admit…it was fun to build…and operate.
At any rate, cold weather aquaponics can present some interesting (and fun to solve) challenges. As well as provide us tastier crops than ones grown during the warmer seasons.
Have you ever tasted frost-sweetened vegetables? Which ones? Share your experiences with us below.