It’s currently 9ºF here in Austin, Texas, and while our Meyer lemon tree is sheltered indoors, I was wondering if it needed chill hours at any point to help it blossom. After some research, here’s what I found.
Since citrus trees are natively from warmer climates, they don’t need chill hours to develop buds into flowers. When it comes to the cold, avoid letting your citrus trees drop below 32°F (0°C), since it could permanently damage them. For best results, cover or bring them indoors.
In this article, we’ll also cover the following about chill hours and citrus trees:
- How temperature impacts their growth
- How cold citrus trees can be before becoming damaged
- Tips for preserving citrus trees when it’s cold outside
Let’s dive in.
Are Chill Hours Necessary?
Chill hours are an allotted time to keep plants below a specific temperature (32-45ºF) to encourage flowering and fruiting.
If you’re growing citrus trees, you don’t have to give them chill hours. Most citrus trees are native to warm, humid environments. With enough sunlight and hydration, your citrus trees will still grow and thrive with plenty of fruit.
So, while citrus trees don’t need chill hours, how do they affect other fruit trees?
- Chill hours allow other fruit trees to break dormancy for maximum fruiting and flowering. Since most fruit trees need this process, they could be slightly stunted if they don’t have enough chill hours.
- Without enough flowers, there won’t be any fruit. Fruit comes from flowers grown on trees, so when your fruit tree doesn’t achieve enough chill hours, it might not flower or grow properly.
Can citrus trees also get these benefits from chill hours?
- While they don’t need chill hours, citrus trees typically aren’t negatively impacted by them. If they’re chilly for days or even weeks, most citrus fruit trees will be fine. We’ll better review the range they can survive and thrive in with the next section.
- Contact the store or company you purchased your tree through if possible. If you’re worried about what type of tree you have or if it can withstand chill hours, they’ll have all the information you need. Know that all citrus trees don’t need chill hours, but there usually aren’t any negative effects if they do get some chill time.
Chill hours aren’t part of the nature of citrus trees. Citrus trees originate in sunny climates that often don’t reach freezing temperatures, so they haven’t evolved with the need for chill hours like many other fruit trees. They’re exceptionally resilient compared to most fruit trees and won’t cease to flower if it gets a bit chilly or warm.
Still, citrus trees aren’t immune to frost damage. Long exposure to below-freezing temperatures can cause harm to every part of the tree.
How Cold Can Citrus Trees Tolerate?
Citrus trees should not fall below freezing temperatures (32ºF, 0ºC). Below this temperature, the plant cells will begin to freeze and die. Depending on how long the tree is exposed to the cold, it can either individually kill flowers, fruit, leaves, branches, or the entire tree.
Here’s what you should know if your citrus trees get too cold for too long:
- The fruit won’t ripen properly. Normally, the tree sends water and nutrition through the branches to develop and ripen fruit. However, if the water inside the tree is frozen, the fruit won’t get what it needs, which can lead to fruit that’s hard and inedible.
- It could rot much quicker than it should. Because of the lack of water and nutrition, fruit can also start to die and rot. This can introduce disease to the rest of the tree.
- Dr. William Johnson at Aggie Horticulture suggests excessively cold temperatures could ruin the wood of citrus trees. Wood needs hydration, much like other parts of a tree. Freezing temperatures limit circulation, causing the wood to become brittle and cracked. It can also break branches that hold fruit.
- The roots won’t grow deep enough to sustain the tree’s growth. In freezing weather, citrus tree roots will also become dormant, which means they’ll stop the uptake of water. This is one of the biggest concerns since, without the ability to absorb water, citrus trees tend to die within a few months.
- Leaves will crumble and dry too quickly due to lack of hydration. For the same reason, the freezing weather limits water to the leaves. This causes leaves to die and when the warmer months do come around, the leafless tree isn’t able to perform photosynthesis and absorb nutrients from sunlight.
Freezing weather can be harmful to all plants. Notice how most frozen regions such as Antarctica, Siberia, and the northwestern territories don’t have the diverse plant life as you’ll find in warmer regions. The good news is that there are methods to protect your citrus trees, regardless of how cold it is outside.
How To Protect Citrus Trees From Frost
Although freezing temperatures can cause irreversible damage to citrus trees, there are a few actions you can take to prevent anything bad from happening. Try one or all of the suggestions mentioned in this subheading to find what works best for your trees. Note that if your citrus isn’t below freezing longer than 30 to 60 minutes, you don’t need to worry about it too much.
Tree blankets are precisely what they sound like. You can use burlap to wrap a citrus tree during excessively frigid nights. Once it warms up, remove the tree blanket, and it’ll be back to normal. Some prefer using tarp covers to wrap or block their trees from the wind and cold air.
Bubble wrap is one of the best insulators. It’s super lightweight, inexpensive, and easy to use. Wrap your citrus trees in bubble wrap if it gets too cold at night. Bubble wrap also has an air gap, which is a plus when it comes to insulation. It also protects your citrus tree from debris, hail, and snow.
Move Your Potted Citrus Trees Indoors
If you’re growing citrus trees in pots, you can store them in the garage overnight. Ensure there’s enough light if you intend to keep them inside longer than a few days. You can either place them next to a window or use a grow-light.
For us, we moved our Meyer lemon tree indoors for a while and put it next to a sunny window. It started to die, but we found out it was because it was near our central heater vent. Once we moved it to a cooler area of the house, it started doing well and even had new growth.
Here’s a quick recap that will help you with your citrus trees and chill hours:
- Since citrus trees are natively from warmer climates, they didn’t evolve to need chill hours.
- Anything below 32°F (0ºC) for longer than 30 minutes can damage the tree.
- Protect your citrus trees by using tree blankets, providing insulation, and storing potted plants in the garage or house.
For more information about protecting citrus trees from frost, watch this video: