The true lemon, Citrus limon, is a small tree reaching between 10 and 20 feet in height. Its true origin is unknown, but it was introduced to Italy by 200 A.D. and cultivated in the middle east by 700 A.D. Although it is more sensitive to freezing that other citrus, it will tolerate cooler summer temperatures and still produce well.
Dig a planting hole that is twice the size of the root ball, and as deep--but not deeper--than the plant's container. Remove the plant from the pot it came in and straighten out any roots that curl around the inside of the pot. If the roots are a tight mass, use a pruning saw to cut into the root ball in three places about 1 inch deep. Prune any visibly damaged roots. Place the tree in the planting hole. Mix some organic matter into about a third of soil that was removed and fill in around the tree. When you've filled in the hole half way, water the tree. This will help settle the soil around the roots. Once the water has drained, finish filling the planting hole. Water the tree again. Remove about 1/3 of the top growth so more of the tree's energy goes into root production.
Fertilize the tree three times a year, only after the tree produces new growth. Application periods will vary based on your location and soil type. In Florida, apply fertilizer between mid-November and the end of April. In California and Arizona, apply fertilizer between February and May. Use a balanced fertilizer that's formulated for citrus trees.
Prune your tree to maintain a height between 10 and 12 feet for better yields. Remove and dead or damaged wood. Opening up the center to let in more light is unnecessary.
Water newly-planted trees thoroughly every day for two weeks. Then water the tree two to three times a week, as needed. The soil should remain moist, but not wet. Adequate moisture is important during and just after flowering for a good fruit crop. Mulching is not recommended.
Protect your lemon trees if the temperature is expected to drop to 28 degrees F. Water the lemon tree when severe temperatures are expected. Moist soil will absorb and release heat better than dry soil. Cover young trees with blankets.
Treat infested plants with an appropriate insecticide. Insect pests include the California red scale, aphids, whitefly and spider mites. Diseases include scab, anthracnose, greasy spot and leaf spot. Spray with an appropriate fungicide.