I’m a big fan of homemade lemonade. Many people who own and grow their own lemons are unsurprisingly fans as well. If you are looking to grow some lemon trees for your own consumption or simply to add an interesting feature to your backyard or property then you need to take a few things into consideration. Frost is one of them. A serve frost could put the health of your lemon tree in great peril.
Overall, the best way to protect your lemon tree from frost is by using coverings, proper pruning, lighting and certain watering mechanisms. The location of where you plant the tree can help, as can the time of year you plant it. Using a frost resistant root-stock also aids in frost damage prevention.
Lights can be attached to the tree in order to warm it up during the night so is it is less likely for it to receive frost damage. You can place a 100 watt outdoor light inside the canopy. Once attached, you can turn this on during the night. Be extremely careful that the light doesn’t come into contact with water. If it does come in contact with water this could prove very dangerous, so caution needs to be taken. An alternative to a powerful outdoor light is to just use Christmas lights that are durable in outdoor conditions. These Christmas tree lights can be wrapped around the trunk and around the canopy branches itself. This can be a great idea in and around the run up to Christmas and the new year. Not only are these lights providing some needed heat for your lemon tree during one of the coldest periods of the year, they also are a great decorative feature during the festive season that your neighbors could admire.
Location of planting
Planting your lemon tree in the right location can do a great deal at reducing frost damage. Having the tree exposed to the sun from a south westerly direction is also beneficial because this means it will potentially receive more sun. It goes without saying that you should bare in mind the sunniest positions in your backyard or property and consider planting you tree there. You should also consider planting your tree on some of the highest points in your backyard, as the air is slightly warmer at an elevated level compared to a lower surface. Additionally, planting your tree by a south facing wall that receives a lot of sun could also be beneficial for your tree. The wall in question may retain the heat from the sun and heat up the tree during the colder evening.
If your lemon tree is very small then you may be able to just wrap plastic sheeting around the entirety of the tree at night. This will do a lot to prevent frost damage. At the other end of the scale, if the tree is extremely tall and well established you may consider putting individual frost cloth or plastic over the trunk and the most important branches with protective.
There is another protective option to consider for small to medium-sized trees. Wooden stakes or plastic pipes can be placed in the ground around the tree at equal distances, each a few inches from the tree’s corners. A sheet of plastic or frost cloth should snugly be able to wrap around them. This will offer protection for the tree. Make sure that the number of pipes are about 12 to 24 inches higher than your lemon tree. This would ensure that covering should easily be able to go over the top of the tree and cover all of it. This simple improvised cover protection, even with plastic sheeting, will do a world of wonders in the prevention of frost and freezing conditions from negatively affecting your tree.
Freezing conditions mightn’t only affect your tree’s branches, but it can also affect tree roots. Therefore, it is favorable if you have a rootstock that can withstand frost and doesn’t become damaged with cold weather. There are several different types of rootstocks that you may consider for your lemon tree before you plant it. Sour orange is an example of a rootstock that is quite good at withstanding frost damage. With that being said it is best to talk to your local nursery or garden center about what rootstock to use. Unfortunately, it is often times hard to get the rootstock that you wish for your tree, as you may only be provided with a select few. Therefore, you should be willing to shop around and look for businesses that offer a wide variety of rootstocks.
Time of Planting
You should hold off planting your lemon tree until about February or March. The springtime could be a preferential time to grow your tree, because if it is grown earlier in the winter a young tree mightn’t be able to cope with the freezing cold weather. If you purchase your lemon tree during the autumn time then you can always just place it in a container and leave it in a warm area near the house. If things start to get really cold then the lemon tree can be easily moved inside the house. When the worst of the winter weather is over you should then try and move your lemon tree to the outdoors. Although, this will do little to prevent the tree from being damaged or frozen in the future, but it will greatly reduce the chances of suffering from frost damage within the first year of you purchasing it which is often the time when such trees are most susceptible to frost damage.
If you water the ground below the canopy then this may help in the fight against frost damage. Moist soil is better at capturing and retaining heat then dry soil. Sprinkling the leaves with water throughout the night can also be an effective anti-frost measure. It needs to be highlighted that the water should continuously flow throughout the night and that there is no break in the flow of water until the morning. By doing this the leaves will be kept at an increased temperature and protected from the frost. This constant flow of water can be turned off once air temperature has increased from the sunlight. The temperature for stopping the flow should be when the air is at about 37 degrees Fahrenheit.
Unfortunately, freezing conditions can do a lot of harm to the leaves and branches of a lemon tree. If a bad frost afflicts your tree then many parts of your tree could be killed. However, you should wait a few months before trying to distinguish what part of your tree are alive and what parts are deadwood. By waiting until the end of spring or into the summer you will clearly be able to see what parts of the tree are dead. Scraping the bark on the part of the tree that you may think is dead can also provide an answer as to whether this tree part is is alive and not. If there is green beneath the bark then it is alive. If not, then it is probably dead.
 The University of Arizona, College of Agriculture and Life Sciences, Protecting a Citrus Tree from Cold (March 2001)