Yes, you can plant a mosquito plant outside, but its ability to survive and return each year depends significantly on your local climate and how you manage it.
"Mosquito plant" is a common name often given to various plants believed to repel mosquitoes. The most prominent varieties include:
- True Citronella Grass (Cymbopogon nardus or Cymbopogon winterianus): This is the source of citronella oil and is a tropical grass.
- Citronella Geranium or Mosquito Plant Geranium (Pelargonium citrosum 'Citrosa'): A scented geranium with a lemon-citronella fragrance.
Understanding Hardiness Zones: Perennial vs. Annual
The key factor determining whether your mosquito plant will thrive outdoors long-term is your USDA Plant Hardiness Zone. This system helps gardeners determine which plants are most likely to survive winter temperatures in their region.
For true citronella grass (Cymbopogon nardus), its growth habit depends on your zone:
- In USDA hardiness zones 9 through 11, true citronella grass is considered a perennial plant. This means it can return year after year, growing from its roots after a dormant period.
- Elsewhere, particularly in zones colder than 9, citronella plants are typically treated as an annual if planted outside. This means they will likely die back with the first hard frost and need to be replanted each spring.
Scented geraniums (Pelargonium citrosum) are generally hardy in USDA zones 9-11 as well, showing a similar perennial or annual behavior based on climate.
Growth Habits by Hardiness Zone
| Hardiness Zone | True Citronella Grass (Cymbopogon) | Citronella Geranium (Pelargonium) |
|---|---|---|
| Zones 9-11 | Perennial (returns yearly) | Perennial (returns yearly) |
| Zones 8 and below | Annual (dies in winter) | Annual (dies in winter) |
Key Factors for Successful Outdoor Planting
When planting mosquito plants outdoors, consider these essential elements to ensure their best growth, whether for a season or for years to come:
- Sunlight: Both true citronella grass and citronella geraniums thrive in full sun, meaning at least 6-8 hours of direct sunlight per day.
- Soil: They prefer well-draining soil. Sandy or loamy soils are ideal. Avoid heavy clay soils that retain too much moisture, as this can lead to root rot.
- Watering: Water regularly, especially during dry spells. Keep the soil consistently moist but not waterlogged. Allow the top inch or two of soil to dry out between waterings.
- Fertilization: While not heavy feeders, a balanced, slow-release fertilizer or a liquid feed every few weeks during the growing season can promote lush growth.
- Protection from Frost: This is crucial for perennial growth. If you live in a borderline zone (e.g., Zone 8) or experience unseasonable cold snaps, cover plants or consider container planting for easier relocation.
Tips for Growing Mosquito Plants Outdoors
To maximize your success with mosquito plants outside, tailor your approach to your local climate:
In Warmer Climates (USDA Zones 9-11):
- Direct Planting: Plant directly into garden beds or borders. Ensure adequate spacing to allow for their mature size.
- Pruning: Prune back leggy growth or spent flowers to encourage bushier growth and more foliage. For true citronella grass, you can cut back old growth in late winter or early spring to make way for new shoots.
- Location: Plant them near outdoor living areas, patios, or entryways where their mosquito-repelling properties can be most beneficial.
In Colder Climates (USDA Zones 8 and Below):
- Treat as Annuals: Simply plant them in your garden beds each spring after the last frost, enjoying their fragrance and foliage throughout the summer, and allowing them to die back in the fall.
- Container Gardening: This is an excellent option for colder regions. Plant your mosquito plant in a pot with drainage holes.
- Overwintering Indoors: Before the first frost, bring potted citronella plants indoors. Place them in a sunny window (south-facing is ideal) and reduce watering through the winter. They may go semi-dormant but can be moved back outside once frost danger has passed in spring.
- Dormancy for Citronella Geraniums: For Pelargonium citrosum, you can also cut them back significantly, bare-root them, and store them in a cool, dark, frost-free place (like a basement) over winter, then repot in spring.
Effectiveness as a Mosquito Repellent
While "mosquito plants" are marketed for their repellent qualities, it's important to understand how they work. The plants themselves don't typically emit enough scent to clear an area of mosquitoes on their own. The mosquito-repelling compounds (like citronellal) are primarily released when the leaves are crushed or bruised.
For best results, consider:
- Strategic Placement: Plant them near seating areas, but also consider occasionally brushing against the foliage to release the scent.
- Companion Planting: Use them in conjunction with other mosquito control methods, rather than relying solely on them.
- Rubbing Leaves: Gently rub leaves on exposed skin (ensure no allergic reaction first) for a localized, temporary repellent effect.
By understanding your hardiness zone and providing appropriate care, you can successfully grow mosquito plants outdoors for their attractive foliage and aromatic properties.
