I'm a kitchen gardening expert and here is what I've learned about how to care for a potted lemon tree in winter

Lemon trees make a fantastic addition to any garden space, though do need protection during winter in many climates. The trees are popular choices to grow in pots on decks or patios and the benefit of growing lemon trees in containers is that they can be moved indoors to shield them from damaging frosts and snow. 

Growing lemon trees in pots is a great way to add these Mediterranean fruit trees to your backyard, and their fragranced flowers and fruit can appear year-round. Citrus trees in pots, however, do need extra maintenance when it comes to watering and feeding.

I spent several years as a professional gardener for the National Trust in the UK, working at a historic garden that had a large citrus collection, which included many lemon trees. This extensive collection of citrus was grown in pots and maintained throughout the year. The lemon trees in pots were housed for winter in an orangery and brought out for the warmer months to create formal displays around the garden.

A simple guide to overwintering lemon trees

Lemon trees are one of the best indoor fruit trees you can grow and their beauty and fragrance can brighten up spaces. However, these citrus trees do benefit from the extra light and warmth of being outdoors for the summer months, where they can bring a Mediterranean garden vibe to your backyard ideas. The trees are not fully hardy, and will need to be protected in winter if you live in a cold climate. There are some important care points to be aware of to overwinter lemon trees successfully.

How to care for lemon trees in winter

Lemon trees can handle low temperatures, but only for a short time. Extended periods of cold weather will harm the trees, so they do need protecting from frosts, cold winds, and snow. 

Lemon trees in pots are at an increased risk of cold weather, as their roots are more vulnerable than when grown in the ground. Before the first frosts are due for your US hardiness zone, you want to proactively start thinking about protecting your lemon trees.

Moving trees indoors 

Lemon trees will overwinter happily in a frost-free and cool location. We used to keep the collection of large lemon trees in an unheated orangery, but the likes of a shed, unheated greenhouse, or garage would do the job if you have a small number of trees. 

Smaller lemon trees in pots can be brought into the house to overwinter - though they will need to be closely monitored for signs of stress throughout their time indoors.

Light and heat

When growing lemon trees indoors, getting the levels of light and heat correct is very important. Light is particularly important when growing citrus inside and you want to make sure that the trees are still getting several hours of direct light a day, even through winter. 

Plants indoors can be kept on a south facing windowsill, while a conservatory or greenhouse is ideal for larger lemon trees in pots. Even if they are in a shed or garage, putting them next to a window can provide enough light to sustain them through the colder months. 

Lemon trees need temperatures of at least 40°F throughout the winter. If the plants are being overwintered indoors it is important to avoid them getting too much heat. This means not placing them near central heating or radiators, as they can struggle with too much dry air that is produced by home heating systems. The stress caused by being placed near fluctuating extreme temperatures can cause the plants to shed leaves.

Watering and feeding 

Reduce the level of watering throughout the winter months. Lemon trees do not like sitting in wet soil, especially during the colder periods. Overwatering stresses the plant and can cause lemon leaves to turn yellow and drop, and it can even lead to root rot if they sit in sodden soil for long periods. 

When watering plants in containers, check the moisture level a few inches down using your fingers. If the soil has completely dried out, then give the lemon tree a deep water and leave it to dry out before watering again. It is recommended to raise pots up on feet to help water to drain away, such as these Garden Gecko Invisible Pot feet available at Amazon.

Fruit trees in pots always need a lot of feeding throughout the year. Lemon trees do benefit from regular fertilization, however the regularity should drop during the winter months. 

In my years looking after potted lemons, the trees were fed every two weeks during the summer and this dropped to once a month once they were moved inside for winter. Use a balanced feed that is formulated specially for citrus trees, such as the Expert Gardener Citrus Plant Food available at Walmart.

Pests 

The likes of aphids, red spider mite, and scale insect can all affect lemon trees and come to the fore when they are indoors over the winter period. Regularly monitor your trees throughout their time inside and act quickly if you spot any signs of pests. 

Spraying trees with insecticidal soap, available at Amazon or other retailers, or a homemade bug spray solution of water and soap, can often be a good way to get rid of aphids or other small pests.

Pruning 

The time to prune a lemon tree is usually from late winter to early spring. Lemon trees do not often require lots of trimming, but plants in pots can be pruned with clean and sharp tools to manage the shape and help promote a bushier tree.

FAQs

The likes of air conditioning, underfloor heating, and indoor fireplaces can all cause potential issues when caring for houseplants in winter. The simple solution of moving plants as far away as you can from extreme heat sources and fluctuating temperatures is all you need to do to protect houseplants from central heating during the colder months.