Lemon trees can fail to flower due to poor care or environmental reasons or if they have not yet reached the age of maturity for flowering and fruiting. According to Purdue University, lemon tree species begin to flower consistently once they reach between between three and five years of age. Beyond the age question, soil quality, watering, fertilizing and temperature are paramount to healthy bud and bloom formation.
Maintain evenly moist, but not soaking-wet soil around your lemon tree with regular deep watering. Ensure that the tree never suffers from drought stress, which can impair bloom formation.
Fertilize your lemon tree with an organic or chemical citrus tree food three times throughout the year. Make the first application in the spring, the second in early summer and the last in early fall to provide a nutritional boost as the lemons mature on the tree. Apply the fertilizer in the dose recommended on the product label and do not overfeed, as excess nitrogen can inhibit flowering. Always apply the fertilizer over moist soil and then water the fertilizer and surrounding soil until the soil is drenched to a depth of at least 6 inches.
Top-dress the soil surrounding your lemon tree under the canopy once or twice a year with several inches of well-aged manure and good-quality compost. This will boost the soil quality without the bad side effects of excess fertilizer, such as the build-up of mineral salts.
Ensure that your lemon tree is growing in full sun exposure with no overhead shade. Lemons require ample sun for robust branch growth, flowering and fruit development and will under-perform without it.
Provide ambient temperatures for your lemon tree at 29 degrees Fahrenheit or above to prevent branch tissue damage or killing of the nascent flower buds. Move container-grown lemon trees indoors when low temperatures are predicted or wrap ground-planted trees in blankets and tarps during the cold period.