Can Rice Plants Survive Winter? An Overwintering Experiment
Last year I grew black forbidden rice (Oryza sativa) for the first time and compared several growing methods. Surprisingly, rice grown in shallow water with azolla performed best in my garden. If you'd like to see how the rice was grown during summer, you can read my earlier article on the rice growing comparison.
This winter I wanted to answer another question: can rice survive winter in my climate, or do I need to start from seed each spring?
Rice is naturally capable of behaving as a short lived perennial in frost free tropical climates, although almost all cultivated rice is grown as an annual crop.
I wasn't sure whether black forbidden rice could survive my cool winters in the Canberra region even with some protection. I decided to protect some plants from frost using several different methods to see whether any would overwinter in my climate until spring.
All of the plants were moved into my unheated greenhouse for the winter. This would prevent the soil from freezing, and would keep the frosts off. Some tender plants, such as chilli and tomato, overwinter easily enough in my unheated greenhouse, while others, such as kangkong or rice paddy herb, usually do not.
I wasn't sure which category rice would fall into, so I decided to find out.
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| Black forbidden rice plants |
Method 1: Overwintering Rice in Soil
Starting out from my rice growing comparison, I had some rice plants in a pot of soil. I moved these into the greenhouse long before the first frost.
These plants had set seed, so I cut off the seed bearing stalks and left all other growth to remain and act as an insulator to protect the plants.
Once the temperatures dipped, all of my rice plants turned yellowish, but they didn't die. As winter went on, all of the plants became increasingly yellow. I didn't remove any of the dead growth in any comparison, as sometimes leaving this can protect the plant just enough for them to survive.
Method 2: Rice in Shallow Water
I grew some rice plants in shallow water for my comparison. I had heard that rice under water tends to rot and die over cold winters.
Rather than risk them rotting under water, I kept my rice plants in their pot of soil, and tipped off most of the water so the soil was damp.
Method 3: Rice in Water with Azolla
I grew several rice plants in shallow water with azolla. The azolla was quite thick, and I wondered if perhaps it could act as a bit of a blanket.
To over winter I kept one pot submerged under shallow water. While I have read that rice plants may rot like this, I was willing to sacrifice one plant to try it. I wondered whether the insulating layer of azolla might improve the rice's chances of surviving winter.
I allowed the water level to drop in most of the other pots. The soil stayed damp, but most of the pot was above water. Kind of like when you grow carnivorous plants in a tray of water. These plants yellowed quickly with cooler weather, and became more yellow as winter went on.
Method 4: Rice with Azolla but No Standing Water
I kept some pots out of water, but covered in their thick blanket of azolla. The soil was never dry, but it was not as damp as the pots that were sitting in a little water.
Like the other treatments, these plants yellowed as temperatures fell and became progressively more yellow throughout winter. As winter went on, the plants all became more and more yellow.
Winter Survival Results
I found the results truly surprising.
Most of winter the foliage and above ground parts died off early in winter, but the roots poking out the bottoms of the pots appeared very much alive.
Then as spring approached...all of them died.
Every plant died, not during the depths of winter as I would have expected, but they died once the weather began to warm.
The ones in soil died, the ones in shallow water died, the ones with a blanket of azolla died. This winter was pretty mild, so I had expected at least one plant to survive if they made it through the worst of winter. For reasons I still do not understand, they died in mid-September once the weather warmed noticeably. I kept the plants for some time, just to see if some dormant part was still alive and would bounce back, but they eventually just rotted.
What I Would Do Differently
I saved seed from my rice plants, and have planted a little of that. So far I have half a dozen plants, which is more than enough to grow some black forbidden rice again. This variety tillers well, and more seed may germinate soon, so I don't know how many rice plants I will end up with this year.
When I try this again, I plan to use larger pots. A larger amount of soil could act as an insulator and keep the plants alive.
Leaving the top growth, and the azolla, to act as a blanket seems good, and I plan to do that again.
Conclusion
Disappointingly, I still don't know if rice can survive my winters with protection.
I plan to try again, but at least now I know if all else fails I can save seed and replant that. Maybe rice should be treated like a tomato plant, and replanted from seed each year in my climate. Or maybe rice will be able to survive my winter and produce a larger and earlier crop the following year. Either way, I plan to save some seed just in case.
Related Articles
This winter survival trial is just one part of my ongoing rice growing experiments. If you'd like to see how the plants were grown, or learn more about some of the methods used, the articles below may be helpful.
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