Summer Squash and Nasturtium
Beneficial Pair — Good Match
Nasturtium's aphid preference is genuinely documented in general, but we haven't seen it isolated specifically for summer squash's fast-cycling new growth. We rate this mixed on the strength of the underlying aphid-trap mechanism being real, while noting the specific squash application remains unconfirmed.
Mechanism: Trap Cropping
As with other nasturtium-and-cucurbit pairings, the mechanism cited is aphid trapping - nasturtium draws aphids preferentially away from a squash plant's tender new leaves and shoot tips. Summer squash's fast, continuous production of new growth through its long harvest window means fresh aphid-attractive tissue keeps appearing all season, which is at least a plausible reason this pairing gets recommended repeatedly for continuously-fruiting squash rather than a one-time crop.
Summer squash's defining trait - continuous production over a long harvest window rather than one concentrated fruit set - is what makes this pairing different from a similar combination with a single-harvest crop, since new aphid-attractive growth keeps appearing well into the season.
Keeping Nasturtium Alive Long Enough to Matter
The practical challenge is that summer squash's own broad leaves grow fast enough to shade out a nasturtium planting within weeks if the two are interplanted too closely, which cuts the trap-crop effect short right as the squash enters its heaviest production phase. Positioning nasturtium at the true outer perimeter of the squash's mature spread, rather than tucked in close early on, keeps it in enough light to survive for the full season.
Spacing
Both plants sprawl low and wide - nasturtium to 8-12 inches, summer squash to 24-36 - which means they're genuinely competing for the same ground layer rather than occupying separate zones, unlike pairings where one plant is tall and the other low.
Watch For
Summer squash's continuous production means new, aphid-vulnerable growth appears constantly through the season, not just early on, so a nasturtium planting that gets shaded out and dies back by midsummer stops providing any trap-crop benefit right when the squash is producing its heaviest flush of new leaves.
Frequently Asked Questions
Would a climbing nasturtium variety avoid getting shaded out the way a bush type does?
It's worth trying. A vining nasturtium trained upward alongside the squash's growth, rather than left flat on the ground, could potentially stay above the expanding canopy instead of getting buried under it. This isn't something we've seen specifically tested for this pairing, but it follows logically from why bush nasturtium struggles here in the first place: it's competing at ground level for the same light the squash is claiming.