Citronella plants are widely recognized for their association with mosquito repellency. However, the term “citronella plant” can be misleading, as it commonly refers to two distinct plant types with different growth habits and repellent properties. Understanding these differences is key to managing their growth effectively in a home garden.
Understanding Citronella Plants
The term “citronella plant” usually refers to one of two botanically different species. True citronella grass (Cymbopogon nardus or Cymbopogon winterianus) is a perennial grass native to tropical Asia. This is the plant from which commercial citronella oil, used in candles and sprays, is extracted. It is a tall, clump-forming grass with long, slender leaves.
Conversely, the plant often sold as a “citronella plant” or “mosquito plant” is typically a scented geranium, Pelargonium citrosum ‘Citrosa’. This plant is not botanically related to true citronella grass. While its leaves release a lemon-like scent when crushed, its effectiveness as a mosquito repellent directly from the plant is generally considered less potent than the extracted oil from the grass.
How True Citronella Grass Spreads
True citronella grass spreads primarily through underground rhizomes, which are horizontal stems that send out roots and shoots. This rhizomatous growth allows the plant to expand its footprint, forming dense clumps. In warm climates, it can grow vigorously, reaching heights of 4 to 8 feet and spreads of 3 to 5 feet.
While a clumping grass, its growth can crowd out smaller plants if not contained. True citronella grass can also establish from seeds, dispersed by wind, water, animals, and machinery, contributing to its spread in suitable environments.
Growth Habits of Citronella Geranium
The citronella geranium (Pelargonium citrosum ‘Citrosa’) exhibits a distinctly different growth habit from true citronella grass. This plant grows as a bushy perennial, forming an upright, mounding shape rather than spreading through underground runners. It typically reaches a height of 2 to 3 feet and a similar width.
This scented geranium does not spread aggressively via rhizomes. While it can self-seed, this is not a vigorous mechanism of spread compared to rhizomatous grasses. Its growth is contained and forms a compact plant, making it a suitable choice for containers or defined garden spaces.
Managing Citronella in Your Garden
Effective management of “citronella” plants depends on identifying which type you have. For true citronella grass, whose clumping habit can become large, containment is recommended. Planting it in large containers can restrict its rhizomatous spread, preventing it from overwhelming other garden plants. Regular division every 2-3 years in spring can help manage its size and vigor.
For the citronella geranium, which does not spread aggressively, management focuses on general care and shaping. Pruning encourages a bushier form and prevents legginess, and removing spent flowers promotes more blooms. While it can be grown in the ground, it is also an excellent choice for patio pots.