You might not have room in your garden for a citrus orchard, but that doesn't mean you can't grow your very own fresh lemons. Dwarf lemon (Citrus limon) trees allow warm-climate gardeners with limited space to fit a fruit-bearing tree in a much smaller area than would be required by a full-size lemon tree.
Dwarf Tree Sizes
Dwarf lemon trees maintain a relatively small size because they consist of a full-size lemon variety grafted onto a dwarf rootstock that limits how tall the tree can grow. A full-size lemon tree may reach up to 20 feet in height, but a dwarf variety may stay as small as 8 feet and is unlikely to get taller than 12 feet, with a spread of 8 to 10 feet. A dwarf lemon planted in a container will be even smaller. Semidwarf trees are somewhat larger and may reach as much as 16 feet in height.
Varieties and Hardiness
Lemon trees, like all citrus trees, are not cold hardy and will be damaged or killed by temperatures that fall below freezing. Most varieties of lemon, including "Dwarf Lisbon," are hardy in U.S. Department of Agriculture hardiness zones 9 to 11. Meyer lemon, which is actually a lemon-orange hybrid of murky origins that reaches a height of only 6 to 10 feet, is a bit hardier and is able to withstand conditions in USDA zones 8b to 10. In any case, lemon trees need to be protected when temperatures approach freezing, and container-grown trees should be brought indoors when frost threatens.
Lemon trees like full sun, so they should be planted in a location that gets plenty of sun exposure throughout the day. They're also sensitive to wind and cold, however, so locations with a lot of wind exposure can be problematic. A location near a south-facing wall that can provide shelter and reflected heat usually works well. Lemons also like loamy soil that's rich in organic matter, and the soil in which they're planted must be well-drained. Lemons don't tolerate standing water, and they'll die in areas where the soil is consistently saturated.
Fertilizaton and Watering
Lemons are sensitive to excess moisture, but they need plenty of water to produce fruit. Therefore, irrigation needs to be consistent so that the soil stays moist but not soggy. Typically, a deep watering once a week will work for a garden tree, but that schedule may need to vary when the weather is especially wet or dry.
Lemons also need plenty of nitrogen to help them flourish. When the tree is two years old, scatter 1/4 cup of an ammonium sulfate fertilizer around the base of the tree in spring and then three more applications at four- to six-week intervals. Increase the amount of each application to 1/2 cup in year three, a cup in year four, 1.25 cups in year five, and 2 cups in year 10.
Pinching the ends of new growth can help the tree stay compact and full, as can pruning leggy young branches. Pruning can be done in any season except winter and should be done with sharp pruning shears or a lopper. Dip the blades of the pruner in isopropyl alcohol or bleach solution after each cut to avoid spreading any infection that might be present.
Pests and Problems
Lemon trees are vulnerable to attack by a variety of insect pests, including ants, mites, scale insects and aphids. Often, spraying the tree with a spray bottle containing water and a few drops of mild dish soap will work to remove the insects. Use a soft toothbrush to scrub away scale insects that are not removed by the spray. Spraying the tree with a commercial horticultural oil product can also help.
Container and Indoor Growing
The small size of dwarf lemons makes them ideal for container growing, an option that allows for growing the trees in slightly colder climates if they're brought indoors during cold weather. A one-year-old tree can be planted in a container with a 6- to 9-inch diameter. Mature trees may need a 16- or 20-inch pot, but transplant the tree into increasingly large containers as it grows so that it's never in a pot that's too big, since it's difficult to maintain proper soil moisture in an oversized pot. When containers are outdoors, keep them in a sunny but sheltered location, and when they're indoors, keep them near a south- or west-facing window.
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