Citrus trees are prized for their fragrant blossoms and flavorful fruit. These evergreen plants have specific needs, requiring consistent sunlight, regular watering, and a steady supply of nutrients to thrive. A successful harvest relies heavily on creating an optimal environment, which means carefully managing the plants situated around the tree. Certain neighbors can undermine a citrus tree’s health and productivity by creating resource conflicts, harboring pests, or introducing maintenance challenges.
Plants That Compete for Essential Resources
The root system of a citrus tree is primarily shallow, with most feeder roots existing in the top 6 to 24 inches of soil, often spreading horizontally up to two to three times the canopy width. This structure makes them vulnerable to competition from plants with aggressive or dense root systems. The presence of competitors in this zone can lead to stunted growth and deficiencies in water and nutrients.
Aggressive, running herbs like mint should be avoided because their underground runners rapidly colonize the soil, choking the delicate, fibrous citrus feeder roots. Similarly, planting turfgrass, such as Bermuda or St. Augustine, directly up to the trunk creates a dense mat of roots that aggressively outcompetes the tree for nitrogen and water. This competition diverts energy from fruit production.
Annual vegetables that are heavy feeders, such as corn or cabbage, also pose a significant threat when planted too close. Corn is particularly demanding, consuming large amounts of nitrogen and water during its growing season, leading to direct nutrient deprivation for the slower-growing tree. Deep-rooted trees like eucalyptus should be kept at a distance of 30 to 50 feet, as they are strong water-suckers and release allelopathic chemicals that inhibit the growth of surrounding plants.
Plants That Harbor Citrus Pests and Diseases
Some plants should be avoided because they act as “host reservoirs,” attracting and sustaining pests that then migrate to the citrus tree. Ornamentals like roses, for example, are aphid magnets, and once a population establishes itself, the aphids, whiteflies, or spider mites will readily spread to the nearby citrus.
The Brassica family, which includes cabbage, broccoli, and kale, attracts pests like aphids and cabbage worms, which can then spread to the citrus foliage. Potatoes should not be planted near citrus, as their growth cycle and harvesting can disrupt the tree’s shallow root system, and they are known to attract root-knot nematodes, microscopic worms that damage root health.
The most direct biological threat comes from other members of the Rutaceae family. While it may seem logical to plant relatives together, they often share the same susceptibilities to diseases, making them vectors for pathogens. Planting other Rutaceae species nearby can accelerate the spread of diseases like citrus canker or citrus greening (Huanglongbing), which are devastating to citrus crops.
Avoiding Plants with Conflicting Environmental Needs
Successful gardening near citrus requires aligning environmental and maintenance requirements. Citrus trees prefer a slightly acidic to neutral soil pH, typically ranging between 6.0 and 7.0, and require well-drained soil to prevent root rot. Plants that require conditions fundamentally different from these will create ongoing issues for the grower.
Planting acid-loving shrubs like blueberries, rhododendrons, or azaleas near citrus is problematic because they require a lower soil pH, often in the 4.0 to 5.5 range. The application of sulfur or acidifying fertilizers needed for these plants will lower the pH of the citrus root zone, leading to nutrient deficiencies in the tree, such as iron or zinc chlorosis. Similarly, plants that demand consistently wet or boggy soil conditions will raise the moisture level in the area, creating an environment perfect for water mold pathogens that cause citrus root rot.
A final conflict arises from incompatible maintenance practices, particularly the use of herbicides. Citrus trees have feeder roots that can absorb chemicals from the soil or through spray drift. Broad-spectrum weed killers, such as glyphosate, used to clear groundcovers can be absorbed by the roots or immature bark, causing leaf distortion, yellowing, and growth setback, especially in young trees.