Citrus trees aren’t typically known for their tolerance to cold temperatures, but some, like the Meyer Lemon, can survive a frost or two. When colder temperatures are approaching, it is essential to pay attention to how cold each of your citrus trees is allowed to get. It takes many years to get a good batch of fruit from a lemon tree, and if unprotected frost damage could take it all away, read on to find out the minimum temperature a lemon tree can handle safely.
Lowest Temperature for an Outdoor Lemon Tree?
An outdoor lemon tree can be wiped out by an unexpected cold snap, an extended cold spell, or cold damage caused by frigid wind chill. Planting in the correct Hardiness Zone between 8 and 11 can help, but even warmer zones have to deal with spontaneous freeze events that can wreak havoc on fruit-bearing trees. Understanding what happens to Meyer Lemon and other citrus trees in freezing temperatures and non-freezing temperatures can help you protect your trees better when the cooler temperatures come.
Below 40°F
This temperature will not harm a mature tree but can halt the growth of young plants. The branches and leaves at the tips of the tree can be damaged if the temperature drops below 40 very quickly and there is less sunlight per day on the lemon trees. Lemons in a canopy of trees will survive better than one or two fruits exposed on exterior branches at these temperatures.
Freezing 32°F
When the temperature drops below freezing, even cold-hardy lemon trees will suffer citrus fruit damage and dropping of blossoms and leaves. Outer branches may begin to die if frigid temperatures continue for several days. It is important to reduce the number of hours an entire tree has exposure to temperatures freezing and below using various citrus plant warming techniques found below.
Below 27°F
This is the critical temperature where citrus fruit begins to freeze. Larger lemons may be able to survive freezing temperatures longer, but at a certain point, all the fruit still on a tree at this temperature will be completely ruined. It is likely that cold damage to the rootball could occur in plants in pots, and it is a good idea to bring the indoor lemon tree inside before it gets this cold in your area.
Can Lemon Trees Survive Frost Outdoors?
If your average winter temperature stays above freezing, then you normally will not need to worry too much about your lemon tree dying. However, if it happens to be an exceptionally cold year, you will need to protect your tree, or you could lose your fruit and have a weak crop next season. Following the steps below can protect your plants without breaking the bank.
Pick All The Ripe Fruit
As the cool temperatures set in, you will want to pick all the lemons off of your tree. Try to get everything cleared before the frost, or you may see damage on some lemons. Moisture buildup in unpruned trees can lead to mold inside the canopy and rotten fruit. Make sure to harvest as soon as it gets cold out to help the tree go into dormancy and protect its leaves and branches from winter weather.
Wrap Trunk with Cardboard
If there will be intense wind chill or a fast frost, you can offset the damage by covering the trunk of your citrus trees with cardboard. The cardboard will block the wind and keep the cold air off of trees. Even raising the temperature a few degrees can prevent irreversible cold damage. Laying some cardboard on the soil can also help lock in some heat and protect exposed roots from cold temperatures.
Place Against a Sunny Wall
Usually, winter days will still provide a bit of heat when the sun is out, and if you set up your yard and potted plants correctly, you can capitalize on that sunshine. Place your trees against a brick wall or lay down black plastic on a patio to capture some of that heat and allow it to be released when the temp drops at night. Active compost piles and chicken coops also generate heat during the winter.
Cover Branches and Crown with Burlaps
If the temperatures will drop well below freezing and stay there for an extended time, you may want to wrap tarps or burlaps over the tops of your trees to shield them from frost and cold damage. Uncover the trees when the sun is at its hottest and recover them to still benefit from the brief winter sun. This may be a nightly task if you are caught in a cold spell and need to save your trees daily.
Protect Pots From Wind
Windchill and string gusts can break brittle fruit-laden branches. If you place potted plants in an area will they receive plenty of sunlight but are not blasted by the wind, they will do better in cold temperatures. Nighttime winds can be especially fierce, so at the very least, cover trees when the sun goes down if you cannot block the wind all day long.
Use Outdoor Lights
If you have ever been to a photoshoot or under studio lights, you may recall they can get hot. Lights generally generate heat, and with the exception of LEDs, that heat can add up to a good amount of warmth. Placing incandescent string lights on citrus trees and turning them on during the night can help generate enough heat to keep your trees alive. Outdoor lights can be positioned to shine on the root zone of trees and increase the soil temperature enough to help your citrus tree stay warm.
Caring for Indoor Lemon Trees
If you can bring your lemon trees inside, you will have a much easier time dealing with the winter. Not having to go out and brave the cold to cover and uncover your tree is all the reason you need to look into moving pots around a few times a year. If you will be bringing your tree inside, try to give it all of these requirements so it can thrive and be ready for a productive fruit season next summer.
| Tree Requirement | Materials | Process |
| Warmth | Heater and warmth-absorbing surfaces | Find the ideal growing range for your citrus trees and place a heater to stay at that temperature |
| Sunlight | South FacIng Window with Direct Sunlight or Grow Lights | Place the citrus tree in the window or shine a light so the lemon tree gets full-spectrum light for at least 8 hours |
| CO2 | Window, Door, or Vent | Allow an air exchange to help keep CO2 levels high for plant development |
| Water | Watering Jug or Bucket | Add water no more than once a week as needed and water in a single deep session |
| Airflow | Fan or Window | Increase airflow to move leaves, strengthen small branches, and reduce the chances of mold or powdery mildew. |
Warmth
The main reason to bring your tree inside is to give it extra warmth during the winter. When the temperatures drop, a tree may spend more time surviving than storing energy in the roots for new spring growth. Anything from blocking windchill to a heater can be used to warm up your fruit trees and recreate the tropical conditions lemon trees love.
Sunlight
Giving your citrus tree 8 hours of sunlight each day can help it store the energy it needs for new growth. Make sure the light you get is full-spectrum, or find a window that gives you all the natural light a growing lemon tree needs. Mylar and other reflective surfaces can be introduced to add more light and help backmost leaves get some extra light while waiting to be rotated to the front.
CO2
This is the air plants breathe, and there needs to be enough of it in the room that houses your lemon tree. Make sure a window, vent, or door can exchange air, or else your lemon tree will be unable to utilize the sunlight for photosynthesis. Small CO2 bags can also be placed in places to release small amounts into the air to help your trees grow even in the wintertime.
Water
Make sure to keep watering your lemon tree when it is moved inside in the winter. Often sprinklers or rainfall water our trees, but when they are brought in, we need to remember to add them to our indoor plant care list. Infrequent deep waterings are best for citrus trees, and the reduced sunlight, heat, and wind will make watering even more irregular than outdoors, but make sure to never water more than once a week.
Airflow
A steady breeze blowing through the leaves and branches has a huge impact on the health and productivity of trees. Without airflow, mildew and fungus could build up, and branches would not build strength to support growth. Weak branches cannot hold fruit and may split or break during seasons of heavy yields, so a constantly blowing fan is your best bet to keep your tree strong all winter long.