How Low Can They Go?

As we approach the cooler seasons of the year, I get asked a lot of questions regarding just how cold is too cold for certain plants! So, let’s break it down!

What is a “Cold Crop”?

Many plants are labeled as “cold hardy”, including a lot of our favorite greens! So, what does that mean? A “cold hardy” plant is one that thrives in cooler temperatures, in comparison to “hot crops” which require warm temperatures to thrive. They are also commonly called “cool crops” or “cold crops”.

Cold crops are best grown in the fall and spring but can be grown all winter long in mild climates. They are usually not susceptible to light frosts. For most cool and cold crops, their ideal daytime temperatures range from 45-80°F.

Multiple Plants

So, how cold can my cold crops get?

Let’s look at a list of our most commonly grown fall and winter greens & herbs here at Planted Places!

  • Arugula: Hardy to 25°F
  • Bok Choy: Hardy to 25°F
  • Chives: Hardy to 0°F
  • Cilantro: Hardy to 10°F
  • Kale: Hardy to 10°F
  • Lettuces: Hardy to 20°F
  • Mizuna: Hardy to 10-20°F
  • Oregano: Hardy to mid-30’s to low 40’s
  • Parsley: Hardy to 10°F
  • Spinach: Hardy to 15°F
  • Swiss Chard: Hardy to 10-15°F
  • Tatsoi: Hardy to 10-15°F

So, can I leave my seedlings outside all fall and winter?

The answer is… maybe! Temperature is a great first indicator of how hardy your plant is. But, there’s a lot more that goes into the equation! Some other factors to consider include:

  • How established the seedlings are: Established healthy seedlings will adapt much better to cooler temperatures, including frost. If your seedlings are young and still establishing, it is best to shield them from freezing temps until they can get established.

  • Microclimates: Microclimates can largely affect temperature. If your plants are in a sheltered sunny spot, they will likely not experience as cold of temps or as hard of frosts as those with an exposed shady or Northern exposure. Try to create or find microclimates to help your plants stay as warm as possible on cool nights.

  • How often your plants experience frost/freezing temps: Most cold hardy seedlings, even young ones, will spring right back from the occasional frost. However, if it is freezing night after night and not warming up much during the day, it may be harder on your plants. Established plants can handle consistently cold temperatures better than younger more susceptible plants.

  • Other weather factors including wind chill, rain & snow pack: Beyond temperature, other weather conditions can also impact our plants. Extreme wind chill, lots of rain and layers of snow can all take their toll on our plants! Be sure to monitor all of these conditions as well.

Putting it all together:

Gardening is as much an art as it is a science. So, while it would be great to have a consistent temperature or formula for when to cover or bring in your plants, that just simply doesn’t exist! There are numerous factors that will affect how our plants will react to different climate conditions.

It’s important that we as gardeners use our instincts to make the best-informed decisions that we can. And hey, we won’t always get it right! But, failing forward (especially with gardening) is one of the best ways that we can learn what to do and not do in the future. It’s all a never-ending process and gardening teaches us to just keep on growing!