Nasturtium Companion Plants: What to Plant With Nasturtiums (and the Aphid Trap Crop)

Nasturtiums are one of the easiest flowers to grow from seed, and every part above ground is edible, so they earn a place in plenty of vegetable gardens. They are also surrounded by more companion-planting claims than almost any other flower. This guide sticks to what extension sources actually list: which vegetables nasturtiums pair with, how the trap-crop idea works (and where it can backfire), and how to sow, place and care for nasturtiums so they bloom all summer.

Good companion plants for nasturtiums

Tomatoes

Nasturtiums are on Virginia Extension's tomato companion list, alongside marigolds, basil, carrots and the onion family. A bush type planted along the sunny front edge of a tomato bed adds flowers for pollinators without competing much for space. Both go out after the last frost. More in what to plant with tomatoes.

Squash, zucchini and pumpkins

Virginia Extension's squash row lists nasturtium with corn and marigold. Squash and zucchini depend on bees to move pollen between flowers, so extra blooms nearby are welcome. Trailing nasturtiums and sprawling squash vines can tangle, so plant bush nasturtiums at the edge of the squash patch rather than in the middle of it. See what to plant with zucchini and what to plant with pumpkins.

Radishes

Radishes and nasturtiums are listed as companions. Radishes are sown early and pulled within weeks, while nasturtiums are sown after the frost, so a nasturtium edge can take over the space as the spring radishes come out. See what to plant with radishes.

Celery

Celery's companion list includes nasturtium. Celery needs steady moisture; nasturtiums tolerate drier soil but bloom better with regular water, so a celery bed suits them fine. See what to plant with celery.

Nasturtiums as an aphid trap crop

A trap crop is a plant that pests prefer, grown so they gather there instead of on your vegetables. Virginia Extension explains that trap crops are sacrificial, and that the pests that collect on them are easier to control in one place. University of Vermont Extension describes nasturtiums as a magnet for aphids, and the Connecticut Agricultural Experiment Station notes that the bean aphid frequently infests nasturtiums.

• Plant them a short distance away from aphid-prone crops (UVM names cabbage and green beans), not right among them, so the aphids gather on the nasturtiums.
• Check them every few days. Clusters of dark aphids on the stems mean the trap is working. Snip off and bag heavily infested stems, or knock aphids off with a strong spray of water, before the colony builds and spreads.
• Leave room for predators. Connecticut's handbook names lady beetles, lacewings and syrphid (hover fly) larvae as natural enemies of the bean aphid. Avoid broad insecticides that kill them too.

What not to plant with nasturtiums

None of our extension sources lists a vegetable as incompatible with nasturtiums. A few practical cautions still apply:

• Cabbage-family crops: UW–Madison Extension lists imported cabbageworm caterpillars among nasturtium's most common pests (the plant contains mustard oils like those in cabbage relatives). Do not count on nasturtiums to protect cabbage, broccoli or kale; if anything, keep them in a separate spot. See what to plant with cabbage for its listed companions.
• Small seedlings: trailing types spread several feet and can smother low crops such as carrots or lettuce seedlings. Use bush types near small plants.
• Self-seeding: NC State notes nasturtiums can self-seed and spread. Pull unwanted seedlings in spring.

Bush or trailing?

UW–Madison and Illinois Extension describe two common garden species: bush nasturtium (Tropaeolum minus), which forms loose mounds, and trailing nasturtium (T. majus), which can spread on the ground or be trained to climb. NC State gives dwarf bush types about 12 inches tall, while climbing types can cover a fence or trellis up to about 10 feet. Bush types suit bed edges and containers; trailing types suit a fence, the edge of a squash patch or a spot where you want ground cover.

When to plant nasturtiums

Nasturtiums are frost-tender. UW–Madison Extension says to sow seed directly in the garden once all danger of frost has passed, or start it indoors in peat pots 4 to 6 weeks before your last frost. Illinois Extension notes they do not transplant well and suggests direct sowing, so if you start them early, use pots you can plant whole. Our planting calendar shows your frost date.

Planting and spacing

• Depth: about ½ inch; the seeds need darkness to germinate (UW–Madison).
• Spacing: 10 to 12 inches apart.
• Soaking: soaking seeds for a few hours or overnight can improve germination; seedlings usually appear in 7 to 10 days.
• Sun and soil: full sun and well-drained soil. They grow in part shade but bloom poorly there. NC State suggests some afternoon shade in very hot summers.

Care: why less fertilizer means more flowers

UW–Madison Extension advises not fertilizing nasturtiums except on extremely poor soil, because high fertility pushes leaves at the expense of flowers; NC State says they grow best in poor to average soil and tolerate drought and neglect. They still bloom more strongly with regular watering. Picking or deadheading the flowers prolongs blooming until frost, and Illinois Extension suggests cutting back leggy plants lightly in midsummer to encourage new growth.

Eating nasturtiums

Illinois and UW–Madison Extension both describe the leaves and flowers as edible, with a peppery, watercress-like flavor. Young leaves are the most tender; older leaves can be bitter, and plants under heat stress taste spicier, so regular watering keeps the flavor milder. NC State adds that the buds, immature seed pods and seeds are edible too, and the pods are sometimes pickled like capers. Only eat plants you have grown or identified yourself, and only if any product you used on them is labeled for edible crops.

Two simple ways to use nasturtiums

1. Tomato bed edge.

   Bush nasturtiums along the sunny front edge of the tomato bed, with basil between the cages.

2. Squash patch border.

   Bush or trailing nasturtiums around the outside of the squash or pumpkin patch, with marigolds, another listed squash companion.

3. Aphid trap strip.

   A short row a few feet from your beans or cabbage-family bed, checked every few days.

Frequently asked questions

What vegetables are good companions for nasturtiums?

Virginia Extension lists nasturtiums as companions for tomatoes, squash (including zucchini), radishes and celery.

Do nasturtiums keep aphids away?

Not by repelling them. University of Vermont Extension describes nasturtiums as a magnet for aphids, so they work as a trap crop: plant them a short distance from aphid-prone crops and remove heavily infested stems.

What should you not plant near nasturtiums?

Our extension sources list no incompatible vegetables. Because nasturtiums can host imported cabbageworm and attract aphids, keep them a little apart from cabbage-family crops and beans rather than right among them.

Should I fertilize nasturtiums?

Usually not. UW–Madison Extension advises fertilizing only on extremely poor soil, because rich feeding produces more leaves and fewer flowers.

Are nasturtiums edible?

Yes. The leaves and flowers have a peppery, watercress-like flavor, and the buds and young seed pods are edible too, provided nothing unsafe has been sprayed on them.