If you want a low-effort, high-impact way to protect vegetables from sap-sucking pests, nasturtiums (Tropaeolum majus) are a top choice. Their lush leaves and sprawling vines act as a magnet for aphids, flea beetles, and cucumber beetles, drawing pressure away from your main crops. But the key to making them work is not just sowing them anywhere—it’s knowing where and when to place them. Done right, nasturtiums reduce infestations, add edible flowers to your harvest, and beautify your beds all season long.
Why Nasturtiums Work as Trap Crops
- Aphid magnet: Their soft, tender foliage is irresistible to black bean aphids and green peach aphids.
- Cucumber beetle diversion: Nasturtiums lure beetles that would otherwise target cucumbers, zucchini, and melons.
- Leafy decoy: Flea beetles often settle on nasturtiums instead of brassicas.
- Edible bonus: Leaves and flowers are peppery, nutritious, and attractive in salads.
- Companion effect: Flowers attract hoverflies, parasitic wasps, and other beneficial insects that then patrol nearby crops.
Placement Principles That Make Trap Crops Effective
1. Edge Planting
Plant nasturtiums at the edges of beds instead of among your vegetables. This creates a perimeter barrier and draws pests outward rather than deeper into the crop canopy.
- Best for: lettuce, kale, broccoli, tomatoes, peppers, cucumbers.
- Spacing: one plant every 45–60 cm along the bed edge.
2. Corner Pockets
Tuck nasturtiums at bed corners where airflow and light are high. Pests naturally congregate on these visible plants, making monitoring and removal easier.
- Works well for raised beds, trellised beds, and container gardens.
3. Between Crop Blocks
If you have distinct crop sections (e.g., a tomato bed beside a cucumber bed), sow nasturtiums in the gap between them. This intercepts pests that migrate across the garden.
- Ideal in four-bed rotations where cucurbits and brassicas alternate with nightshades.
4. Under Trellises
Let trailing nasturtiums sprawl beneath vertical crops like beans, peas, or cucumbers. Their ground cover lures pests downward and away from fruiting vines.
5. Perimeter Rows in Row Gardens
For larger plantings, dedicate a full outer row of nasturtiums. This approach works like a “living fence,” keeping pressure concentrated on the sacrificial plants.
Timing for Maximum Effect
- Direct sow at Last Spring Frost (LSF): Nasturtiums germinate easily and don’t like transplant shock.
- Resow mid-summer: A second wave ensures strong coverage through late season when aphids peak.
- Succession every 6–8 weeks: In longer growing seasons, stagger sowings to replace declining plants.
Practical Trap Crop Strategies
- Tomato Bed: Place nasturtiums along the south edge. Aphids cluster on nasturtiums, leaving tomato leaves cleaner.
- Cucumber Bed: Train nasturtiums at the bed lip while cucumbers climb. Beetles stay busy at the ground level.
- Brassica Bed (Kale, Cabbage, Broccoli): Plant nasturtiums at row ends. Flea beetles prefer them, easing brassica leaf damage.
- Pepper Bed: Use nasturtiums in corner pockets where aphid buildup is easiest to clip or compost out.
Maintenance & Monitoring
- Inspect weekly. Check trap plants for pest colonies; once heavily infested, remove and dispose of the plant (don’t compost if pests are active).
- Replant as needed. Keep spare seeds to replace pulled trap plants quickly.
- Don’t rely solely on them. Trap cropping is most effective when paired with mulching, crop rotation, and beneficial insect habitat.
- Cut back vines. Nasturtiums sprawl; trim runners if they compete with crops.
Common Mistakes to Avoid
- Planting too close. If nasturtiums are inside crop rows, pests can easily spread back to your vegetables.
- Neglecting removal. Trap crops must be managed; leaving infested nasturtiums in place risks boosting pest numbers.
- Single sowing. Nasturtiums decline in midsummer heat; without resowing, trap function fades.
- Overcrowding beds. Sprawling nasturtiums can smother small crops like lettuce if not pruned.
Small-Space & Container Adaptations
- Balcony tomatoes: One nasturtium in a side pot can divert aphids effectively.
- Grow bags: Plant nasturtiums at the outer edge of cucumber or pepper bags.
- Patio boxes: Mix trailing nasturtiums on the sunny side, letting them cascade down rather than cover soil.
Frequently Asked Questions
Do nasturtiums really keep pests off crops?
Yes, but only if managed properly. They concentrate pests, which must then be removed or destroyed to prevent spillover.
Should I grow trailing or bush nasturtiums as trap crops?
Trailing types work well on edges and under trellises. Bush types are better for tight beds or container edges.
Can I eat nasturtium leaves and flowers if they’ve trapped pests?
If plants are visibly infested, avoid harvesting from them. Grow extra nasturtiums in separate spots for edible use.
How many nasturtiums do I need per bed?
For a standard 1.2 m x 2.4 m bed, 4–6 plants on edges or corners usually provide strong coverage.
Will nasturtiums attract beneficial insects too?
Yes—hoverflies, lacewings, and parasitic wasps visit their blooms. This adds a second layer of protection.
Bottom Line
Nasturtiums are more than pretty flowers—they’re strategic decoys that draw pests away from your main crops. The trick is edge and corner placement, succession sowing, and removing infested plants before pests spread. With just a handful of nasturtiums in the right spots, you can make a noticeable difference in pest control while adding color, edible blooms, and diversity to your garden beds.