It can be difficult to grow lemon trees outdoors if you don't live in their preferred tropical climate. Luckily, dwarf varieties of lemon trees such as Meyer lemons (Citrus x meyeri) can be grown in large containers in the home or in a greenhouse, so long as they get ample light. Sun rooms, large bay windows and most any large, south- to southwest-facing window can provide enough light to grow and enjoy your lemon tree indoors.
Transplant a nursery-grown Meyer lemon tree into a very large container. The bigger the container, the better. At minimum, a 30-gallon size container will provide room for a decent root system for your lemon tree. The container should have drainage holes at the bottom and a saucer to catch water. Because of the size of the pot, it's easiest to do the transplanting near where you'll be housing the lemon tree.
Fill the large container one-half to two-thirds full of potting mix. The University of Minnesota recommends a lemon tree potting mix of equal parts potting soil, finished compost and vermiculite or perlite. Water this in so it settles.
Hold the lemon tree on its side and gently pull it from its original container by the lower trunk. You may need to work the sides of the pot with your palm to work the root ball loose from the pot. Work the bottom roots loose gently, especially if the tree has become root-bound.
Set the root ball down into the pot easily. Add more potting mix below the root ball or take some away so that the top of the root ball is 1 inch below the top of the large container. Add more potting mix around the sides of the root ball until it is filled to 1 inch below the top of the pot. Add water as you go to settle the soil and remove air pockets.
Set the potted lemon tree in the brightest area in the house. If it's close to a window don't let the leaves come into contact with the window pane, as they can burn when the sun heats the glass.
Water when the top inch of soil is dry. Continue watering until water comes out the drainage holes in the bottom. Avoid watering too frequently, as this can rot the roots.
Rotate the pot a quarter turn every two weeks if the light is more intense on one side of the plant than the other. The more light your lemon tree has, the greater the chances of it producing blooms and a few fruits.
Fill a spray bottle with water and 1 tsp. of dish soap. Spray the leaves, top and bottom, whenever you rotate the pot. Washing the leaves will help discourage spider mites, scale and whitefly. If whiteflies become a problem, hang strips of insect trapping tape from the lower branches and from the ceiling above the tree.
Move the tree outside during the summer months when the temperature is over 65 degrees F, if possible. Allow the tree to acclimate to sunshine in the shade of another tree or on the north side of the house for about a week before moving to full sunshine.