Citrus trees, which include popular varieties like lemons, limes, and oranges, are beautiful evergreen additions to any garden, providing fragrant blossoms and delicious fruit. Successful citrus cultivation, whether in the ground or in a container, depends on meeting their specific environmental and nutritional needs. These subtropical plants are not difficult to grow, but they do require a consistent and informed approach to thrive outside of their native warm climates.
Establishing Your Citrus Tree
Choosing the right location is the first step in successful citrus growing, as these plants require a significant amount of direct sunlight to maximize fruit production. Select a site that receives a minimum of six to eight hours of full sun each day, ideally with a southern exposure. A location that is sheltered from strong, cold winds will also help protect the foliage and young branches from environmental stress.
The soil must offer excellent drainage, as citrus roots are highly susceptible to rot in waterlogged conditions. If the native soil is heavy clay, planting the tree on a raised mound or amending the area with organic matter can improve aeration and permeability. Citrus prefer a slightly acidic soil pH, and high alkalinity can interfere with nutrient uptake, leading to deficiencies.
When planting, the hole should be two to three times wider than the root ball, but no deeper. It is important to position the tree so the graft union, the swollen point where the fruiting variety meets the rootstock, remains several inches above the surrounding soil level. Immediately after planting, water the tree deeply to settle the soil around the roots and eliminate any air pockets.
Nutritional Requirements and Watering Schedules
Citrus trees are heavy feeders and require a comprehensive fertilizer that supplies both macronutrients and specific micronutrients. Nitrogen (N) is the element needed in the largest quantity, supporting vigorous leaf growth and fruit development. A fertilizer formulated specifically for citrus, often with a slightly higher nitrogen ratio, should be applied regularly throughout the active growing season from spring through summer.
Micronutrient deficiencies are common and often appear as a distinctive pattern of chlorosis, or yellowing, on the leaves. For instance, an Iron (Fe) deficiency typically presents on new growth as yellow leaves with the veins remaining dark green. Zinc (Zn) and Manganese (Mn) are also frequently deficient, and these issues are often compounded in highly alkaline soils where the nutrients become chemically unavailable to the tree roots.
Watering technique differs based on whether the tree is planted in the ground or in a container, but the rule of avoiding overwatering remains constant. In-ground trees should be watered deeply and infrequently, allowing the soil to dry out between applications to a depth of about five or six inches. For trees in containers, check the soil moisture by hand; when the top two inches feel dry, water thoroughly until it drains from the bottom.
Seasonal Protection and Structural Pruning
Providing protection from temperature extremes is necessary for citrus, especially in climates that experience occasional freezing temperatures or intense summer heat. Before a predicted frost event, ensure the soil is thoroughly moistened, as wet soil retains and radiates more heat than dry soil. For young or sensitive trees, cover the entire canopy with a frost blanket or burlap, making sure the material extends to the ground to trap warmth.
To provide supplemental heat during hard freezes, strands of old-style incandescent holiday lights can be wrapped around the branches beneath the cover. It is also important to wrap the trunk of young trees with insulating tree wrap to protect the vulnerable graft union from freezing. Potted citrus should be moved indoors to a bright location before temperatures drop below freezing.
Pruning serves two main purposes: promoting air circulation and establishing a strong structure. The best time for structural pruning is typically in late winter or early spring before the new flush of growth begins. Focus on removing dead, damaged, or diseased wood, along with any suckers that sprout from the rootstock below the graft union.
Identifying and Managing Common Pests and Diseases
Regular inspection of your tree is a foundational practice in Integrated Pest Management (IPM), allowing for the early detection of threats. Common insect pests include scale, aphids, and spider mites, which are all sap-sucking insects that can weaken the tree and lead to sooty mold growth. Scale insects often appear as tiny, immobile bumps on stems and leaves, while aphids congregate on new, tender growth.
Management of these pests often begins with cultural control, such as controlling ant populations, which protect scale and aphids in exchange for the sugary honeydew they excrete. Horticultural oil sprays, such as neem oil or mineral oil, provide an effective, less toxic treatment option by smothering many soft-bodied pests. For more mobile pests like the citrus leafminer, which causes serpentine trails on new leaves, the damage is mostly cosmetic, and treatment is often unnecessary.
Certain diseases present a significant threat, including Citrus Greening (Huanglongbing), which is transmitted by the Asian citrus psyllid. Symptoms of this bacterial disease include blotchy yellowing on leaves that can be confused with nutrient deficiencies. Citrus Canker is another bacterial disease that causes raised, corky lesions with a yellow halo on fruit, leaves, and stems, and infected material should be removed immediately. Finally, Phytophthora Root Rot, a fungal-like disease, is a direct result of poor drainage and persistent overwatering, causing the roots to decay and the tree to decline.