From an Agriculture standpoint, growing food in the Winter is literally what Florida does best. Cooler temperatures plus less hours of sunlight means a longer growing season, but the presence of less pests and better weather to harvest in makes up for the longer time between planting and harvesting.
We do get the occasional freeze here, and it can have dramatic impact on food farmers if the freeze wipes out a crop. This is a rarity, however, and for the most part, Florida does its best growing starting in the Fall through the Winter time.
In today’s blog I wanted to highlight some fun and helpful facts about cold-hardiness and best practices for Gardening in Florida’s Winter.
The Biology of Vegetable Antifreeze Systems
Many veggies labeled “cold tolerant” are labeled as such for a reason. These particular vegetables have mechanisms in their biochemistry that protect them from the effects of cold with minimal intervention.
Have you ever heard people say that their lettuce or kale or carrots taste sweeter having been through some cold weather? Well, they weren’t kidding!
First, when the weather starts to get cooler, plants start to manufacture their own antifreeze sugar solution that helps to keep the water in the cells from freezing. This process happens over time as the plants are exposed to cool weather (about 60 degrees F or below). This is a self-preservation tactic of plants to prepare for colder weather so that they can continue to survive with little to no damage.
Additionally, many of these cold-tolerant plants have an additional failsafe tactic. They increase the amount of fat-based compounds into their cell walls to give the cellular structures some extra flexibility in the event that the plant DOES have the water frozen inside of it.
Side note about physics: When water freezes, it expands. Ever frozen a bottle of water that was too full and found the plastic cracked? That’s what happens to plant cells of plants that don’t have extra cold protection mechanisms – the cells burst and the plant turns to mush.
And finally, cold-tolerant plants have a final secret weapon to minimize the effects of freezing: They release the water inside the plant through the leaves to freeze on the OUTSIDE of the plant. You’ll see these plants wilt during the freeze and then spring back to life when the air warms up again.
Plants are pretty brilliant, are they not?
Not All Veggie Plants Are Prepared
Unfortunately, we can’t save them all. Not all veggie plants can weather a true freeze. Crops that are considered Spring and Summer plants are excluded from Winter Gardening for the most part (except you adventurous souls who tell me they grow tomatoes all year round and “risk it”…oh wait…that’s me too…lol).
This is because the plants that are Spring/Summer crops don’t possess the nifty anti-freeze making and fat-insulating capabilities of their Fall/Winter brethren. It’s simply not in their DNA. If they’re tropical zone rated only (Ag Zones 10 and up), they most likely won’t survive no matter what you do. At least not the current leaves. The roots/rhizomes may survive and if so they’ll sprout again in the Spring when the daylight hours extend again. You’ll just have to be patient!
There are certain veggie plants that survive better in the cold and possible freezing temps. I know we’ve talked about some of them in past blogs! Here I wanted to remind you and add to the list, with a little bit of the nerdy science behind their amazing frost-proofing qualities. Knowing that helps you prepare your garden for the weather appropriately!
Past Post #2 – Grow These in Florida This Winter, November 2018
Past Post #3 – Top 5 Winter Garden Ideas, February 2018
Here’s a quick guideline chart for good stuff to grow in Winter and their cold temperature threshold.
Keep in mind a few things:
- Some individual cultivars of different plants are more susceptible to freeze damage than others.
- Preconditioning is so important! If you have a season that goes from balmy to suddenly frigid overnight and the plants have had no time to become cold-tolerant, the plants haven’t had time to adapt and use their innate freeze-warding systems, and they will likely succumb.
- Remember wind and humidity are also factors, not just cold (N-Sulate Freeze Cloths are FANTASTIC for controlling these factors! In fact that’s what they’re built for!)
- Temperatures that are 20 or below for significant periods of time will affect even the cold hardiest plants, slowing their growth and production, possibly degrading their harvest production, even if it doesn’t kill them.
When Freeze Damage Happens Anyway
Often freeze damage to cold-hardy plants happens due to dehydration – as we learned above, these plants “compartmentalize” their susceptibility to freezing by moving their water supply to outside the leaves. So, some freeze “burn” is simply dessication, or complete lack of water. It’s like mummifying your leaves.
Normally your leaf tips will succumb first, or the smallest youngest leaves that are exposed.
This is caused by low humidity (which often accompanies cold weather) and harsh wind taking the water that the plants excreted out of their leaves and moving it away from the plant. Leaves can take water in through their leaves as well on a limited basis. But when the wind dries that water off, it’s gone, never to be recuperated by that immediate leaf. Sometimes the roots can’t get the water to the leaves fast enough and the leaves “burn”, or mummify.
Many times this doesn’t mean your whole plant is dead. You can remove the damaged leaves and often the plant will regrow and recover when it warms up again – if there’s other leaves that can perform photosynthesis or an established root system that can restart the growing.
For more information on recovering from a freeze check out this blog article:
The best thing to do is to use a frost cloth cover when you know there’s a freeze coming. Used as directed, these cloths insulate the plants from the cold by trapping warmth from the ground inside a bubble, and also keep the wind from blowing away any water that the plants have extruded from the leaves, controlling the local humidity. Basically, it covers everything needed to protect the plants from freeze.
I hope that this was a helpful article for you. When I scan the gardening groups I see literally hundreds of questions about preparing for a freeze and what can be done for plants that can’t be moved indoors. I just wanted to try and help our readers understand the science behind cold and the plants that can, and can’t, handle it.
Until next time, Keep Growing!