The nasturtium — cheap, bright and edible — now fronts a push for low-spray veg beds. Early adopters report fewer aphids and steadier tomato growth, achieved with a packet of seed and a steady hand on the hose.
A spring shift in pest control
Allotment holders and balcony growers face the same seasonal headache. Aphids arrive before tomatoes harden off, sapping vigour from the youngest leaves. This year, many are turning to a tactic from family plots of old: trap planting with nasturtiums placed as buffers around tomatoes.
Reports from kitchen gardens suggest a 70–80% drop in tomato aphid pressure when nasturtiums sit 50 cm from each plant and receive light, regular care.
The method rests on behaviour. Aphids prefer the tender growth and scent of nasturtiums. They settle there first. That shift buys time for tomatoes to establish stronger stems and thicker foliage, which tolerate brief visits far better than weak seedlings.
How nasturtiums reroute aphids
The trap-plant effect
Nasturtiums act as a decoy. Their soft shoots form a landing pad for incoming greenfly, concentrating colonies on a plant you can prune, pinch or even compost away. The tomatoes sit just beyond, shielded by that living “firebreak”. Ladybirds and lacewings also find their larvae’s first meals there, which strengthens natural control.
Placement that works
Gardeners place nasturtiums as a ring or border around tomato rows. Keep a 50 cm gap to limit root competition while staying close enough to intercept the first wave of pests. Maintain a low, airy canopy so aphids keep settling on the decoy rather than moving deeper into the bed.
- Sow nasturtiums two weeks before planting tomatoes out.
- Drill 2 cm-deep furrows, 30 cm apart; drop one seed every 15 cm.
- Water with a fine rose daily until seedlings stand firm.
- Mulch lightly to stabilise moisture without smothering seedlings.
- Pinch the most infested tips to keep the trap attractive and active.
Timing guide: sow April to May, germination in 7–14 days, then maintain a steady, gentle water routine for 10 days.
What gardeners report once growth begins
By June, many see nasturtiums teeming with aphids while tomato leaf tips stay clean. The practical gains look clear: fewer curled leaves, steadier flowering trusses, and less sap loss during the key early push. The effect depends on density and upkeep. One sparse row rarely pulls enough pressure. A border sown at 15 cm steps often does.
Numbers to watch
Expect visible colonisation on nasturtiums first. If tomato leaf undersides remain mostly clear for three weeks after planting out, the system works. Gardeners aiming for a roughly 75% reduction tend to sow at least one 3–4 metre nasturtium strip for every 6–8 tomato plants, then adjust after the first warm spell.
Soil, feeding and water: keep the balance tight
Nasturtiums favour poor to moderately rich soil. That suits the job. Overfeeding tomatoes with nitrogen draws aphids back to the crop. Use about 2 litres of well-rotted compost per square metre and resist heavy fertiliser early on. Keep water regular but light. Stress invites pest swings; soggy roots do the same.
A small maintenance routine pays off
Check borders twice a week. Pinch the worst tufts on nasturtiums, but leave enough infested growth to hold the crowd. If one clump gets overwhelmed, remove that section and let fresh shoots regrow. The trap works when living and renewing, not when stripped bare or left to collapse.
Costs, trade-offs and impact
Seed costs stay low and sowing takes minutes per metre. The gains include fewer sprays, calmer growth and edible flowers for salads. The trade-off is management. You guide the pests rather than eradicate them. That approach also reduces collateral damage to pollinators and predatory insects.
| Approach | Typical cost | Observed aphid reduction | Notes |
|---|---|---|---|
| Nasturtium trap border | £2–£4 per packet | 70–80% on tomatoes | Needs pinching and spacing at 50 cm |
| Soft soap spray | £5–£8 per bottle | Fast knockdown, short-lived | Repeat after rain; risk to beneficials if misused |
| Do nothing | £0 | Unpredictable | Often heavy early damage on young plants |
When 75% is not enough
Warm, still weeks can trigger surges even with traps. Add gentle tactics rather than abandon the system. A handheld water jet dislodges clusters on nasturtiums. Yellow sticky cards show pressure trends. Companion a few umbellifers, such as dill, to attract hoverflies, whose larvae clear aphids quickly.
Risks to manage
Aphids can carry viruses. The trap reduces exposure but does not seal tomatoes off. Keep the 50 cm gap, avoid overcrowding, and remove heavily wilted nasturtium sections before winged aphids disperse again. Rotate the trap border each spring to fresh soil to limit disease carryover.
Set-up details that raise success odds
The first ten days matter most. Sow into warm soil, water with a fine spray, and shield seedlings from wind. Stressed nasturtiums attract fewer aphids early on, which weakens the decoy effect. Once plants knit, you can ease off. Keep feeding modest. Tomatoes need strength, not lush, sappy growth that lures pests back.
Keep it simple: sow early, space at 15 cm, hold a 50 cm moat around tomatoes, and prune the trap little and often.
Beyond tomatoes: wider uses and quick maths
Trap planting scales. Nasturtiums also pull flea beetles from young brassicas in some sites, while marigolds help with whitefly near cucumbers. Each pest responds to a different lure, so match the attractant plant to the crop and space it to intercept the first wave.
A brief calculation helps. One packet sows a 6–8 metre border. If that border spares two trusses per plant on six tomatoes, and each truss ripens 4–5 fruits, the saved harvest can clear the seed cost many times over. Add the edible flowers and the border earns a second use in the kitchen.
Key takeaways for this spring
- Sow nasturtiums in April–May, about two weeks before tomatoes go out.
- Keep rows 30 cm apart and seeds 15 cm apart, 2 cm deep.
- Hold a 50 cm gap between trap and crop to limit competition.
- Pinch infested tips to keep the lure active through summer.
- Aim for a 70–80% cut in aphid pressure, then fine-tune density.
For small spaces, a ring of two or three nasturtium plants around a patio grow bag already shifts the balance. For large beds, border both windward and sunny edges. Treat the trap as a living tool, adjust it as weather changes, and let beneficial insects do the quiet, daily work that sprays often interrupt.
