Updated: Jun 15, 2021
Now that the weather is getting consistently colder, you may begin to think about protecting your frost sensitive plants to help them survive. What does it mean for a plant if it is frost sensitive? Also, how do you help keep these frost sensitive plants alive?
Plants are typically 80% - 90% water. When water freezes, it expands, causing plants to swell. When they receive warmth, they begin to thaw and they shrink. Late in the spring or early in the fall this principle can wreak havoc in a sensitive plant if the change is drastic.
Many plants are perfectly suited to handle the fluctuations of temperature. These are known as Frost Tolerant plants. Biennial plants like kale, cabbage, carrots, onions, are examples. As well as many perennial trees and shrubs and lots of other flowers are frost hardy or frost tolerant.
Some plants cannot survive even the slightest freeze, these are known as warm weather crops. These include the annuals that you sow or transplant after the last frost, like squash, peppers, sunflowers, etc. Some climates can actually support these plants year round due to the lack of frost. Of course this is not the case for most high elevation farms or gardens, and that is why today we are focused on the frost sensitive plants, which are in-between these two groups.
Frost sensitive plants typically include soft fruiting bushes and trees, like legumes, tomatoes, fruit trees, herbs, and some others. They can survive slight frosts, but are more prone to damage because of them.
When frost sensitive plants experience a freeze and the moisture content expands, they are technically still alive. However when the frost passes and the sun comes out, they can essentially explode on the molecular level if thawed too quickly. That is what makes them frost sensitive.
Frost sensitive plants can also be frost hardy! But how can this be?
The answer is in microclimates. Most growing locations have various microclimates. This is basically where the environment is consistently different than the surrounding area on average. Some are warmer due to lack of shade, angle of the land (toward the sun), or lack of moisture. Some are colder due to being positioned away from the sun, being positioned under leaf cover, or perhaps they are in the shade of a building. Wind exposure also plays a large role. You can easily create these microclimates with some intuitive planning.
This is how you help frost sensitive plants!
It may sound backwards but frost sensitive plants can actually perform better in the colder microclimates. The reason is that when a plant is in a shady or sheltered location, it takes longer for the plant to thaw from a freeze. This works in two ways. In cold climates it forces these cold sensitive plants to stay dormant longer into the spring, usually once the warm season has officially arrived. The other way is by allowing them adjust easier when it has experienced a freak or unexpected freeze late in the spring or early in the fall.
A lot of fruit trees and bushes actually benefit from being planted in a shady location. Whole crops can be lost from an unexpected frost after flowering, and this way that risk is minimized. As well, fruit develops better when it is chillier on hot summer days, making them sweeter and even more nutritious! So the cooperation with these frost sensitive plants is essential to making the most out of your garden.
Hopefully this clears up some confusion surrounding frost sensitive plants, establishing the difference between frost tolerance and sensitivity. As well you should be better suited to planting and growing these frost sensitive crops, saving you some wasted effort and seed.
Be sure to follow High Altitude Homestead for more no-nonsense know-how when it comes to growing a garden or farm at high elevations!