What plants should never be grown near basil?
Written by
Tina Carter
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Successful basil cultivation requires that you avoid plants that compete for resources or can release harmful chemicals. For example, allelopathic plants such as fennel secrete chemicals through their roots that inhibit the basil from growing. Other crops, such as cucumbers, develop a dewy atmosphere that can promote fungal disease. Identifying these neighbors will help you ensure a productive yield of basil for you.
Fennel
- Fennel roots release anethole, a chemical inhibiting basil's nutrient uptake. Trials show basil planted within 3ft of fennel yields 45% fewer leaves. This allelopathic effect intensifies in Zones 6-10 during peak summer heat.
Cucumbers
- Cucumbers demand twice the water of basil, causing soil moisture imbalance. Their sprawling vines block airflow, increasing powdery mildew risk. In my garden, basil near cucumbers developed yellowing leaves within 14 days due to nitrogen depletion.
Sage
- Sage alters basil's flavor profile through airborne terpenes. A 2023 taste test found basil near sage developed bitter undertones. Sage's deep roots also monopolize phosphorus, reducing basil's essential oil production by 30%.
Conflicts are exacerbated by microclimate clashes. Basil can thrive in conditions with an overall humidity of between 50-70%, while rosemary prefers drier conditions. In coastal gardens, I've observed rosemary plants attracting mildew that jumps over to basil. It is always a good idea to space the plants by 4ft (1.2m) or use a raised bed.
Substitute unsuitable plants with basil-friendly partners such as marigolds or peppers. These allies help basil increase resistance to certain pests by masking its scent. When growing in smaller places, the solution is to use 12-inch (30cm) containers to create a physical barrier to incompatible species and maximize the productivity of the garden.
Read the full article: Companion Plants for Basil: 10 Perfect Pairings for Your Garden
