Growing lemon trees indoors is popular in many parts of the country. At 3 to 5 feet tall, they make an excellent houseplant next to a sunny window, or in a greenhouse. By keeping the trees indoors, they are not subjected to the climate fluctuations, and are able to remain lush and green year round. If properly cared for, you can even produce your own lemons from an indoor tree. When purchasing your lemon tree, look for one that is 2 to 3 years old.
TIP: Our expert gardening advisor, Rachel Klein adds, "Given the right conditions, you could grow your own lemon tree by planting a grocery store variety lemon seed. However, these trees could grow to be 20 feet tall! Instead, buy a nursery store lemon tree. These are usually dwarf varieties, like the Meyer Lemon."
Keep it Sunny
The most important thing for growing lemon trees indoors is to make sure that they have plenty of light. For the best growth, provide your lemon tree with 6 to 8 hours of direct sunlight a day, however, it can be placed in a darker corner and given artificial light. It might be a good idea to install artificial lighting at least during the winter, when the plants needs 8 to 12 hours of sunlight to flourish. The leaves will be a dark green if there is enough light, and begin to yellow around the edges when not enough is provided.
TIP: Rachel says, "Lemon trees thrive with an average temperature of 70 degrees F during the day and 55 degrees at night. If temperatures dip below 55 degrees F, the tree will go into dormancy."
Water your lemon tree often. The soil shouldn't be wet, but it should always be kept moist. Citrus trees live in wet environments, and are able to resist excessive soil moisture far better than the shock of dry soil. It cannot be stressed enough that plenty of moisture is important not only for the growth of the lemon tree, but for it to be able to grow juicy fruit as well. Select the right size container for your tree. A 2 to 3 year old lemon tree prefers to grow in a "5 gallon" (12 inch diameter) nursery pot. Make sure it has adequate drainage holes.
TIP: Rachel suggests, "Do not water your lemon tree if the surface of the soil is dry without checking the moisture at root level. This will lead to over watering. A simple moisture meter, available at garden supply stores, is an inexpensive way to measure exactly when your tree needs a drink."
Moisture and Misting
Humidity is important to proper lemon tree care. Citrus trees are at home in regions where the humidity is often 70 percent or higher and daily summer rains are commonplace. To mimic this, use a spray bottle and give the plant a light misting once or twice a day (more like a heavy dew fall than simulated rainfall). Or, wipe the tree down with a soaked sponge. This light misting allows moisture to be absorbed directly by the leaves, which in turn allows easier transference of moisture to the fruit where it is needed most.
Fertilizing a Lemon Tree
Once a month, dissolve 1 cup of sifted compost in 1/2 gallon of water. Over the course of a week, use this fertilized water on the plant, mixing it up well before each application. Alternately, mix a thinner solution by adding more water, and use it daily. Citrus trees need a lot of organic compounds from the soil, so rejuvenating it often will have beneficial results. Lemon trees prefer a slightly acidic soil, so use a peat moss based growing mix.
TIP: Rachel adds, "If using a commercial fertilizer, select one that is high in nitrogen, such as a 2-1-1 or 3-1-1 preparation. In some regions, you may be able to find specialized citrus/avocado fertilizers. Follow the package instructions for application."
Pruning a Lemon Tree
After the budding and fruiting season has passed, prune the lemon tree to keep a nice rounded shape. If you do not prune the tree back occasionally, it will quickly expand past what is acceptable for an indoor plant, and lose the natural rounded shape of the plant crown. It is not a good idea to prune branches during the bloom or fruiting seasons, as too much of the energy of the lemon tree is being allocated to the growth of new fruit and leaves.
Indoor and Outdoor
During the summer, when the weather warms up, move your lemon tree to a sunny spot outside. If the tree remains indoors during the entire season, bees and other insects will be unable to pollinate it. Though some trees can effectively self pollinate indoors, a little help can go a long way to increase harvest size. Place the tree outdoors in the summer unless you want to pollinate it by hand. To pollinate by hand, use a small paintbrush or cotton swab to brush pollen into the flowers.
Prune Fruit Clusters
As the lemon tree is blooming, you will notice that 2 or more clusters of fruit appear at each bud. As the fruit begin to grow, remove all but one or two of the fruit, giving the remaining ones more access to vital nutrients and encouraging healthier fruit growth.