Growing Citrus Indoors

Several species of citrus are excellent houseplants if the proper environmental conditions are met. 

Citrus trees are easy to purchase online or at local garden centers. Purchase grafted plants as this helps keep trees more compact (under 6 feet) compared to full-sized trees that reach over 20 feet. Citrus can be grown from seed, but the size and flavor of the fruit may be inferior.  Additionally, seed-grown citrus is much more likely to have long, sharp thorns (which can be cut off if needed) and grow to a very large size, often outgrowing its indoor location.

Species  |  Care  |  Flowering & Fruiting  |  Propagation  |  More Information 

Species to Consider for Indoor Environments

There are several species that are popular with home gardeners for their abundant fragrant flowers and occasional fruit.

Care

Light

All citrus prefer bright, direct light when grown indoors during the fall and winter. A west- or south-facing window that receives at least 6 to 8 hours of direct light is often required for citrus trees.  If needed, provide supplemental light.  Citrus can acclimate fairly well to low light levels but will not flower and fruit if they don't get enough direct light.

Moving Outdoors

Move your citrus outside for the summer to a partial shade location to take advantage of the better growing conditions and abundant light.  It is essential to acclimate plants when moving them outdoors in the spring.  Move plants outdoors once nighttime temperatures are in the 50s°F.  In the fall, move plants indoors once nighttime temperatures drop below 50°F.  More information, including details on acclimating, can be found in this article: Moving Indoor Plants Outside for the Summer.

Temperatures

While citrus trees benefit from being outside in partial shade during the summer months, they will not overwinter outdoors in Iowa.  Warm temperatures are essential. Plants prefer 65-85°F during the day and 55-65°F at night. Temperatures below 50F can cause leaf loss. Freezing temperatures or lower are lethal. 

Soils

Citrus plants also insist on moist but well-drained soils that are slightly acidic. Too much water and the roots rot. Too little water and the plant starts dropping leaves. In winter, place a humidifier near the plants to keep them healthy and thriving. 

Fertilizer

In spring and summer, citrus benefit from fertilizers.  Apply a slow-release fertilizer in April or May, and it will continue to lightly fertilize plants through the spring and summer months.  

Pruning

Plants can be pruned any time of the year to help control their size and balance the plant's crown.  Always remove branches back to their point of origin to promote a natural shape.  Most commercial types of citrus are too large for indoors, so buying a variety grafted to dwarfing rootstock is beneficial.  Always remove any suckers that form from below the graft union as soon as they are noticed.

Potential Pests

Citrus attracts several insect pests like spider mites, whiteflies, and scale. Inspect plants frequently for insects.  Wash leaves occasionally to prevent insect infestations.  When pests are observed take immediate action to eliminate the problem.  If you choose to use insecticides, be sure they are labeled for edible fruit plants.  Always follow all label directions, including the pre-harvest interval, should you plan to harvest the fruit. 

Flowers and Fruit

In late winter or early spring, citrus may bloom indoors. Their highly fragrant flowers are welcome by indoor gardeners.  

Pollination

Not all citrus will set fruit without the assistance of pollinators.  This means the gardener sometimes must transfer the pollen from one flower to another to ensure fruit set. If the plant is blooming but not setting fruit, manually transfer pollen.  

Manual pollination can be done in several ways.  You can "play bee" and use a small paintbrush or cotton swab to move pollen from flower to flower.  You can shake the plant or gently flick the flowers when the pollen is ripe to spread the pollen.  Sometimes, pollination can be achieved by setting a fan to move the flowers around and help transfer pollen.

Once pollinated, the fruit will form.  Gardeners will have to be patient as fruit often takes 6 to 9 months to fully mature and ripen on trees grown indoors.

Lack of Flowers

Flowers are not always a given, especially when plants don't receive enough light and nutrients.  Since it can be difficult to have reliable flowering and fruit set, it may be better to grow citrus as a lovely houseplant and treat any fruit that may form as a pleasant surprise.  

If you are not seeing flowers (and the subsequent fruit), it is typically due to insufficient light or nutrients.  Moving plants outside for the summer can help provide the abundant light needed for flowering.  Fertilizing regularly, as outlined above, will also promote blooms.

Some species and cultivars of citrus will bloom on an annual cycle, often developing flowers in spring for fruit harvest in fall or winter.  Other types, including lemons, limes, and kumquats, will flower and fruit year-round.

Citrus must see a temperature drop of about 5 to 10 degrees F from day to night.  Without this nighttime drop in temperature, plants will not flower.

Propagation

Citrus can be propagated in several different ways.  

Cuttings

The most reliable way to propagate citrus is with stem cuttings.  This type of propagation produces a genetic clone of the parent plant, ensuring you will have the same tasty citrus.  If the cutting material is harvested from a grafted citrus tree, the propagule will not be dwarfed and could grow quite large.  Learn more about this propagation method in this article: How to Propagate Houseplants by Stem Tip Cuttings.

Seed

Citrus is relatively easy to grow from seed harvested from within the fruit.  The seedlings will be similar to the parent plant but not identical, and these plants seldom set fruit, and when they do it is typically inferior.  Seed-grown citrus often develop large thorns and get too large to grow indoors. Learn more in this article: Can I germinate the seeds from a grapefruit?  

Grafted

Most dwarf varieties purchased from garden centers are grafted. By selecting the right rootstock, desirable cultivars and types of citrus can be dwarfed, allowing you to have the desired fruit on a smaller tree that fits better indoors.  Grafting is challenging to do at home, but it is possible.  It looks much like the grafting of any fruit tree.  Learn more in this video: Grafting Fruit Trees.

More Information

• How to Care for Houseplants
• Indoor Plants (PDF)
• Diagnosing Houseplant Problems
• Propagating Houseplants
• Growing Indoor Plants Under Supplemental Lights.
• Moving Indoor Plants Outside for the Summer

Photo credits: 1: Cindy Haynes; 2: DimaBerlin/AdobeStock; 3: Cindy Haynes; 4: Remberto/AdobeStock