How to Grow a Key Lime Tree Indoors or Outside

key limes growing on a branch — Credit:
Getty / Constantine Johnny

If you enjoy decadent foliage, delicate flowers, and a bountiful harvest, then a key lime tree is a great choice. These plants will thrive outdoors in a consistently warm environment, but they can also be grown in containers with the right care.

Growing one of these trees at home is a wonderful way to indulge in homemade key lime pie, bars, and more. Here's how to properly care for them, according to experts—no matter where you live.

Lisa Tadewalt, an ISA-certified arborist and co-founder of Urban Forest Pro
Caroline Ervin, landscape designer and owner of The Georgetown Garden Shop
Ondrea Kidd, lead floral designer and founder of Sowing Joy Farm

When to Plant

A key lime tree has beautiful evergreen foliage and can be grown indoors or outside.

“[They] can be planted in USDA zones 10 through 11 any time of year, but it's best to plant in spring or early fall when the soil temperatures are not too cold or too warm,” says Caroline Ervin, landscape designer and owner of The Georgetown Garden Shop.

Lisa Tadewalt, an ISA-certified arborist and co-founder of Urban Forest Pro, prefers to get a locally grown key lime tree that's already accustomed to living indoors. “Then it doesn’t matter what time or year you plan to plant [it],” she says. “Indoor trees are not held to the same planting restrictions that outdoor trees are.”

How to Plant

When planting a key lime tree outdoors, Ervin suggests these steps:

Dig a hole that's a bit wider and the same depth as the root ball. It's best to loosen the soil at the bottom of the hole.
If your soil is in poor condition, mix in some organic conditioner and sand.
Place the tree in the hole, ensuring the flare of the tree trunk sits just above the soil surface.
Fill the hole around the tree and firmly press the soil around the rootball.
Thoroughly water the soil, and make sure that any air pockets are removed.
Apply a light layer of about 2 to 3 inches of a natural mulch—such as triple-shredded hardwood and pine straw—to help retain moisture, keep the soil temperature more consistent, and suppress weeds. Remember not to pile mulch right next to the tree trunk.

When planting a key lime tree in a container, Ervin suggests similar steps:

Choose a large container—at least 27 inches wide and 24 inches deep—so there's ample space for the roots to grow.
It's very important that the planter has at least one hole in the bottom so that it can drain, which will prevent root rot. If no holes exist, create them in the container before you plant.
Add about 2 to 3 inches of gravel at the bottom of the container to help with drainage.
Place a piece of filter fabric. This is a geotextile that will allow water to flow through, but will keep the soil from settling in between the pieces of gravel.
Partially fill the container with quality organic potting soil and set the tree in the container so the top of the root ball is about 2 inches below the top of the container.
Fill the container with more potting soil, packing it firmly around the root ball. The flare of the trunk should just barely sit above the top level of the soil.
Water the container thoroughly, and make sure all air pockets are removed.
Apply a light layer of about 2 to 3 inches of a natural mulch—such as triple-shredded hardwood and pine straw—to help retain moisture, keep the soil temperature more consistent, and suppress weeds. Remember not to pile mulch right next to the tree trunk.

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Care Instructions

Follow these best practices to help your key lime tree thrive.

Temperature: It's important to keep your tree in an area that will not drop below 50 degrees Fahrenheit, says Ondrea Kidd, lead floral designer and founder of Sowing Joy Farm.
Sunlight: Ervin says key lime trees need at least six to eight hours of bright, direct sunlight for optimal growth and fruit production.
Fertilizer: Fertilize your key lime tree regularly using a citrus-specific fertilizer, says Kidd. “Fertilize in early spring and add new compost, making sure that all roots are covered,” she says. “Make sure to only apply it to the dirt around the tree, as key lime trees can burn if the fertilizer touches the trunk or foliage.”
Water: Key lime trees, both in the ground and in a container, like consistent moisture—but don't overwater. Ervin recommends watering deeply and thoroughly and allowing the top inch of soil to dry between waterings. Keep in mind that trees in a container will dry out faster than trees planted in the garden. “A tree with too little water may show signs of curling or drooping leaves,” she says. “A tree with too much water will have yellowing leaves.”

How to Repot

When potting up a key lime tree, choose a container that is only slightly larger than your existing pot.

“Remove the tree from its old pot and loosen any circling roots,” says Kidd. “Also, remove any roots that appear to be dead or damaged. Then, plant the tree in the new pot using fresh, well-draining, and slightly acidic potting mix at the same depth. Backfill with soil, making sure to cover all roots, then water in well.”

Pruning Tips

Key lime trees do have thorns, so Ervin advises pruning with caution. However, it's an important process.

“Pruning can help maintain the shape of the tree, allows for good air circulation, and encourages new growth,” she says. “[It's] best in winter or early spring before new leaves begin to grow. Remove any crossing branches to improve air circulation, and thin some branches in the canopy to allow light to reach all parts of the plant."

Of course, remove any dead or disease branches as needed—and remember to clean your pruners with rubbing alcohol between sessions.

How to Overwinter

Temperatures below 35 degrees Fahrenheit can severely damage or kill a key lime tree, so bring the tree indoors once the overnight temperatures drop into the mid-40s.

“Even in winter, the key lime tree will need direct sunlight for six to eight hours to thrive,” Ervin says. “Pick a bright, sunny location with southern or western exposure, and monitor the soil to make sure the tree has consistent moisture."

Common Pests and Diseases

Like many citrus plants, key lime trees are susceptible to leaf miners, scale, and aphids. “Monitor the tree for any signs of pests, and use organic products to manage them,” says Ervin. “Neem oil, insecticidal soaps, or even a simple spray of dish soap and water will work.”

“Citrus canker is another disease affecting key lime trees, which causes raised, cork-like lesions on the leaves, stems, and fruits, and can lead to defoliation of the tree,” says Ervin. “To manage this, prune off all affected areas of the tree and apply copper-based sprays to prevent [it] from returning.”

Frequently Asked Questions

How long does it take for a key lime tree to bear fruit?

A key lime tree can bear fruit in its first year, Tadewalt says. However, it will often take several years for a newly planted key lime tree to produce fruit.

“The trees flower in the spring and fruits develop later in spring or summer,” Ervin says. “If the flowers fall off the trees before creating new fruit, it just means the tree is not yet mature enough to bear fruit.”
Do key lime trees grow well in pots?

Growing key lime trees in containers allows you to protect them and control their environment, ensuring a healthy tree.

“Make sure the container is large enough to accommodate the tree's roots, and closely monitor the soil to make sure the moisture is consistent,” says Ervin.
How tall does a key lime tree get?

Typically, key lime trees can grow 6 to 12 feet tall. “They do grow more quickly when planted outdoors in the ground,” Ervin says, “but definitely can thrive when grown in containers.”

In pots, Kidd says they will only reach six feet or so. “The dwarf varieties can reach six feet outside and 3 to 4 feet in a container,” she says.
Do key lime trees need to be hand pollinated?

Key lime trees are self-pollinating, so a single tree can bear fruit. However, it’s often better to have several trees to produce a bigger harvest.

You can also significantly increase fruit production by hand pollinating. Use a soft tool, such as a Q-tip or small paintbrush, and go from bloom to bloom.