How Cold Hardy Are Collard Greens

Collard greens are surprisingly cold hardy and can survive temperatures as low as 10°F (-12°C) once they’ve been properly hardened off by gradually cooling weather.
 
If you’ve been wondering how cold hardy collard greens really are, the short answer is very cold hardy, especially compared to other leafy greens like lettuce or spinach.
 
These tough, leafy vegetables actually get sweeter after a frost, which is one of the reasons Southern gardeners love growing them through the fall and winter.
 
In this post, we’ll dig into just how cold hardy collard greens are, what temperatures they can handle, and how to help them survive the coldest nights of the year.
 
Let’s get into it.
 

How Cold Hardy Are Collard Greens Really?

Collard greens are cold hardy enough to keep producing through light freezes and even some hard freezes with a little protection.
 
Most varieties can handle temperatures down to about 20°F (-6°C) without much trouble, and mature plants can often survive dips into the low teens.
 
That’s impressively cold hardy for a leafy green, and it’s why collard greens are a staple in fall and winter gardens across the South.
 
Here’s what makes them so tough:
 

1. Collard Greens Have Natural Antifreeze Compounds

One reason collard greens are so cold hardy is that they produce natural sugars and other compounds that act like antifreeze inside their cells.
 
When temperatures drop, these compounds lower the freezing point of the water inside the plant, which helps prevent ice crystals from forming and damaging the tissue.
 
This is also why collard greens taste sweeter after a frost, since the plant converts starches into sugars to protect itself.
 

2. They Thrive in Cool Weather

Collard greens are a cool-season crop at heart, which means they actually prefer cooler temperatures over the blazing heat of midsummer.
 
Their ideal growing range is between 45°F and 75°F (7°C to 24°C), and they’ll happily keep growing as long as the soil isn’t frozen solid.
 
That natural preference for cool weather is a big part of why collard greens are so cold hardy compared to warm-season greens.
 

3. Mature Plants Are More Cold Hardy Than Seedlings

The older and more established your collard greens are, the more cold hardy they become.
 
A mature plant with a thick stem and plenty of leaves can shrug off temperatures that would kill a young seedling.
 
So if you’re planning to grow collard greens through winter, it’s best to get them in the ground early enough that they’re fully grown before the first hard freeze hits.
 

4. Hardening Off Makes a Big Difference

Collard greens that have been gradually exposed to cooling fall temperatures become far more cold hardy than plants that get hit by a sudden freeze.
 
This process, called hardening off, triggers the plant to build up those protective sugars and compounds we mentioned earlier.
 
So a collard green plant that’s been through a few light frosts is much more cold hardy than one that’s only ever known warm weather.
 

What Temperatures Can Collard Greens Survive?

How cold is too cold for collard greens?
 
Here’s a quick breakdown of what you can expect at different temperatures:
 

1. Light Frost (28°F to 32°F)

Collard greens handle a light frost with zero problems.
 
In fact, this is when they start getting sweeter and more flavorful, so don’t panic when you see frost on the leaves.
 

2. Hard Freeze (20°F to 28°F)

At these temperatures, collard greens are still cold hardy enough to survive, though the outer leaves may get a bit damaged.
 
A layer of mulch or a floating row cover can help protect them and keep them producing.
 

3. Deep Freeze (10°F to 20°F)

This is where collard greens start to struggle without protection.
 
With a thick layer of mulch and a row cover, they can often pull through, but you may lose some leaves.
 

4. Below 10°F

Once temperatures drop below 10°F, even the most cold hardy collard greens are at serious risk.
 
At this point, your best bet is to harvest what you can and hope for the best with the rest.
 

Tips for Growing Cold Hardy Collard Greens

If you want to push the limits of how cold hardy your collard greens can be, here are a few tips:
 

1. Plant in Early Fall

Timing matters when it comes to cold hardy collard greens.
 
Plant them early enough that they have time to mature before the first frost, but late enough that they miss the worst of the summer heat.
 

2. Mulch Heavily

A thick layer of straw or leaves around the base of your collard greens helps insulate the soil and protect the roots from freezing.
 

3. Use Row Covers

Floating row covers or cold frames can add several degrees of protection and make your collard greens even more cold hardy.
 

So, How Cold Hardy Are Collard Greens?

Collard greens are very cold hardy and can survive temperatures as low as 10°F with proper protection.
 
They get sweeter after a frost, they thrive in cool weather, and mature plants are tougher than seedlings.
 
With a little mulch and a row cover, you can keep harvesting cold hardy collard greens well into winter.