Small dimensions, glossy-green leaves and fragrant white flowers make the Meyer lemon tree (Citrus x meyerii) a desirable houseplant for cold-winter climates. Meyer lemon normally grows outdoors in U.S. Department of Agriculture plant hardiness zones 9 through 11, where the temperature rarely dips below freezing. When grown indoors, it may not fruit without pollination assistance.
Potting Mix and Fertilizer
Grow Meyer lemon in a pot with drainage holes that's at least 1 inch deeper than its nursery pot. Use a porous, well-drained commercial potting mix or make your own with equal parts of sterilized potting soil, perlite and peat moss.
Starting one month after planting until its growth rate slows in early fall, fertilize every two weeks with high-nitrogen, 30-10-10 fertilizer for acid-loving plants.Dissolve 1/2 teaspoon, or the brand's specified amount, of the fertilizer in 1 gallon of water and pour it around the plant.
Don't fertilize from late fall until the first flush of new spring growth appears.
Light and Temperature
Give the tree between 8 and 12 hours of daily sunlight. Strong, direct spring and summer sun that weakens slightly in winter is ideal. The best location is in an unobstructed window with southern or southwestern exposure.
Where that's not possible, five or six hours of direct daily sun supplemented by 3 to 6 hours beneath timer-equipped, full-spectrum fluorescent plant lights is adequate. Set the lights far enough above the tree that its topmost foliage remains cool.
The tree performs best with indoor temperatures of around 65 F in the daytime and 55 F at night.
Water and Humidity
An indoor Meyer lemon needs consistently moist -- not saturated -- potting mix. When the mix feels slightly dry to the touch, water until fluid runs from the drainage holes.
To compensate for winter's dry, furnace-heated air, set the pot in a drainage saucer containing a layer of pebbles barely submerged in water. As it evaporates, the water increases the humidity around the tree. Top off pebbles as necessary. Misting with a spray bottle of water every other day also helps.
Spider mites, whiteflies and scale insects occasionally infest indoor Meyer lemons. Spider mites spin fine webs on the backs of the leaves, whiteflies swarm from the plants when disturbed, and scales look like tiny barnacles clinging to the stems and branches. Whiteflies and scales also cover the leaves with sticky honeydew.
Discourage the pests by periodically rinsing the leaves with water. Treat existing infestations with ready-to-use insecticidal soap. Move the tree out of direct sun, cover surrounding objects and spray until the soap drips from both sides of the leaves. Repeat weekly, or as often as the label recommends, until the problem subsides.
Dress in protective clothing, including waterproof gloves, safety goggles and a respiratory mask and follow the label application instructions when working with insecticides.
Pollination by Paintbrush
The lack of natural pollinators is the biggest drawback to growing Meyer lemon indoors. To compensate for missing bees and butterflies, use a soft-bristled artist's paintbrush to transfer pollen from one flower to another. If the transfer takes, the flowers drop their stamens and petals and tiny lemons develop.