How to Grow Citrus Indoors
The amazing orangery at the gardens of Versailles, with more than 1,000 perfectly kept potted plants, might be the world's most famous showcase of citrus trees, indoors or out. But you don't need to be Louis XIV or have nearly as grand a setup to grow, display, and even harvest citrus at home.
The best pick for homegrown citrus is a dwarf variety, a plant that is grafted onto special rootstock that prevents the tree from growing too large. Many citrus trees can be grown as dwarves, including Meyer lemon, kaffir lime, and 'Trovita' and calamondin oranges, which are amenable to indoor cultivation.
Soon enough, you could be harvesting oranges for marmalade, preparing desserts with Meyer lemons, or picking kaffir lime leaves for an authentic Thai curry. What a wonderful way to beat the winter blues.
For a plant that will produce fruits and blossoms right away, choose a two-to three-year-old dwarf tree. Calamondin orange trees, which have a high tolerance for indoor conditions, are a good choice for beginners. Buy one from a reputable nursery to avoid diseased or inferior plants. We like Four Winds Growers.
A vessel with adequate drainage is essential. Select a clay, ceramic, or plastic pot slightly larger than the root ball. It should have several holes at the bottom. Fill the drainage dish with stones to provide air circulation.
Well-drained soil is also crucial. Use a slightly acidic (pH 6 to 7), loam-based potting mix. Better yet, buy premixed potting soil formulated specifically for citrus trees.
Most citrus trees require eight to 12 hours of sunlight daily. When growing them indoors, position your plants beside a south-facing window with good airflow. If necessary, supplement sun with a grow light during dark winter months.
Dwarf citrus perform best when temperatures stay between 55 and 85 degrees; an average of 65 degrees is ideal. And they dislike abrupt temperature shifts, so be sure to protect them from chilly drafts and blazing heaters. Avoid spots near exterior doors, radiators, fireplaces, and ovens.
Come spring, the tree can spend more time outdoors, being brought inside during cold spells. When all threat of frost has passed, slowly acclimate your citrus tree to its new outdoor home by placing it in a semishaded spot for a few days, then slowly bring the tree into the sun. It's very important to make a slow, smooth transition to avoid shock and scorched leaves. Select a protected location in full sun with good airflow. Patios, balconies, and terraces are all great spots. To move the tree indoors for winter, slowly reverse the process well before the first anticipated frost date.
Care and Watering
Regular watering is key. Adding pretty, decorative mulch (such as pebbles or moss) will help reduce evaporation and retain moisture at the critical surface-root zone. But keep in mind that your tree's potting soil should be kept on the dry side of moist, particularly in winter, to prevent fungal infections and root rot. Using a water meter (available at most garden centers) to measure the soil's moisture level will help. Citrus trees also like moist air. Positioning your plant near a humidifier or regularly misting the leaves with a spray bottle will help keep foliage looking its best in dry winter months.
From spring to summer, feed your tree every three weeks with a high-nitrogen fertilizer made for citrus (a tomato and vegetable formula can be substituted). Feed half as often in fall and winter.
Watch for Pests
Citrus are vulnerable to scale, spider mites, mealybugs, and aphids. Be on the lookout for early signs of infestation: curled, speckled, or yellowing leaves; sticky residue; and silky webs between the branches. Use the least toxic treatments available, such as insecticidal soap or neem or horticultural oil, to combat pests as needed.