Lemongrass (Cymbopogon citratus) is a tropical, clumping grass valued for its rapid growth and distinct citrus aroma. Successful gardening involves recognizing antagonistic planting, where one plant negatively affects another’s growth. To ensure a productive harvest, identify which plants should not share space with lemongrass. These negative interactions stem from either direct competition for resources or the release of growth-inhibiting compounds into the soil.
Competition for Water and Nutrients
Lemongrass is a vigorous, heavy feeder that forms dense clumps, demanding significant water and nitrogen to support its tall stalks and extensive root system. This tropical perennial thrives in rich, moist soil and full sun, relying on consistent moisture and regular fertilization. Its expansive root mass quickly occupies the surrounding soil, making it a formidable competitor for any nearby plants with similar resource requirements.
When high-demand plants are placed too close to the lemongrass clump, the neighbor’s growth is often stunted due to resource depletion. The fibrous roots of the lemongrass intercept available water and nutrients, particularly nitrogen, before they can reach less aggressive plants. This intense competition is especially detrimental to shallow-rooted vegetables and herbs. The sheer size of a mature lemongrass plant also creates significant shade, further hindering the growth of sun-loving neighbors.
Chemical Interference in Growth
Beyond physical competition, certain plant interactions are governed by a process called allelopathy, where one plant releases biochemicals that can inhibit the germination or growth of another plant. While lemongrass itself is known to contain allelochemicals that can suppress the growth of certain weeds, the primary concern is avoiding common garden plants that are strongly allelopathic toward their neighbors.
Allelopathic plants produce compounds that leach into the soil or are released from decaying foliage, negatively affecting the surrounding environment. For instance, the black walnut tree releases juglone, which is highly toxic to many vegetables. Fennel is also notorious for releasing compounds that inhibit the growth of almost all nearby plants. Placing such species near lemongrass can create a toxic soil environment that stresses all plants, compromising the health and performance of both.
Actionable List of Avoided Plants
To ensure a thriving garden, certain plants should be kept at a distance from lemongrass, primarily due to intense competition or allelopathic properties. Plants with dense or aggressive root systems, such as mint, should be avoided or grown in containers to prevent them from directly competing for space, water, and nutrients. Mint is a vigorous spreader that will aggressively colonize the same soil space required by the clumping lemongrass.
Plants to avoid near lemongrass include:
- Root vegetables: Shallow-rooted plants like carrots and potatoes should not be planted nearby. Their growth is easily suppressed by the grass’s root mass and its high demand for nitrogen.
- Cabbage family members: Heavy feeders such as broccoli, kale, and cabbage conflict with lemongrass’s needs. These brassicas prefer cooler conditions, which are at odds with the tropical requirement for consistent moisture and warmth.
- Allelopathic herbs: The strongly allelopathic herb fennel should never be planted near lemongrass, as its root exudates inhibit the growth of many herbs and vegetables.
- Moisture-sensitive herbs: Herbs such as rosemary and sage are poor neighbors because they thrive in drier conditions, contrasting sharply with the moist soil lemongrass requires for optimal growth.
To minimize negative interactions and ensure adequate resources, maintain a distance of at least 18 to 24 inches between a mature lemongrass clump and any neighboring plants.