Repellent plants: which ones should you sow to keep mosquitoes and aphids away?

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“Plant lemongrass and you won't have any more mosquitoes.” You read that everywhere, and it's false — not because the plant contains nothing active, but because an intact plant releases almost nothing into the air.

Repellent compounds are enclosed in microscopic glands on the surface of the leaves. They are released only when the foliage is crushed. A pot of lemongrass placed on a terrace, without anyone touching it, has practically no effect.

That does not mean these plants are useless — they are, but in a different way. Here's what really works and how to use it.

How a repellent plant really works

Three distinct mechanisms, with different levels of effectiveness.

Passive diffusion — the plant spontaneously emits volatile compounds. The effect is very weak and highly localized, extending at most a few dozen centimeters, and it disappears with the slightest draft. This is what people overestimate.
Release through crushing — crushing the leaves ruptures the glands and releases the essential oils all at once. The effect is clear, but lasts only a few dozen minutes.
Masking the host plant's scent — in the vegetable garden, an aromatic plant masks the chemical signal by which an insect identifies its host plant. This is the most useful mechanism, and it works without intervention.

Keep the distinction in mind: against mosquitoes, crushing is essential; in the vegetable garden, masking works on its own — provided the plant is truly right next to the crop to be protected.

Against mosquitoes, on a terrace

Plants that actually contain something

Lemongrass and lemon geranium — rich in citronellal and geraniol. These are the molecules actually used in commercial repellents, but at concentrations far beyond what a plant emits.
Lemon balm — very rich in citronellal, and by far the easiest of the group to grow. Rubbed on the skin, it produces a real, though brief, effect.
Pennyroyal — traditionally considered the most effective against insects. Warning: its essential oil is toxic; do not use it internally or on children's skin.
Catnip (catmint) — its nepetalactone is being studied for its repellent properties. It has one notable drawback: it attracts every cat in the neighborhood.
Lavender — a moderate but real effect, and also an excellent nectar source for bees.
Basil — on a terrace table, a pot that you crush from time to time does more than a decorative pot.

How to use them effectively

Place them within reach — on the edge of a table, along a path, or by the entrance. A plant you never touch is useless.
Crush a few leaves before settling in, and rub them on your wrists and ankles if the plant is not irritating.
Group several pots together rather than leaving one isolated — the mass of foliage matters.
Combine this with a fan if you have a terrace: mosquitoes are poor flyers, and a light breeze is more effective than any plant.

The measure that really matters: eliminate standing water. Plant saucers, buckets, gutters, watering cans, tarps. A tiger mosquito can develop in a bottle cap of water, and no plant can make up for a breeding site ten meters away.

Against aphids in the vegetable garden

Here, the approach changes completely: the goal is not to repel, but to redirect and regulate. And it is much more effective.

What really works

Nasturtiums as trap plants — they massively attract black aphids, which leave nearby crops alone. Plant them along the edge, upwind of the prevailing wind. They are not repellent: they are sacrificed, and you have to accept seeing them covered in aphids.
Flowers for beneficial insects — this is the main lever. Dill, coriander, yarrow, borage, marigold. Hoverfly and ladybug larvae consume aphids by the hundreds — but adults feed on nectar. Without flowers, there are no larvae.
Summer savory near beans — a traditional pairing against black aphids, with a moderate but documented effect.
Interplanted aromatic herbs — thyme, sage, basil, mint. A real scent-masking effect, provided they are in the row, not two meters away.

Other pests

Pest	What helps	Mechanism
Carrot fly	Leeks, onions, and chives in alternating rows	Crossed scent masking — the best-established effect of all
Cabbage white butterfly	Mint, thyme, sage, tomatoes nearby	Scent masking
Flea beetles	Mustard as a trap crop, away from cabbages	Diversion
Whitefly	Basil at the base of tomato plants	Scent masking, partial effect
Nematodes	French marigold as dense cover	Substances released by the roots — a few plants are not enough
Ants	Tansy, mint	Contact repellency, to be placed along their paths
Slugs	Nothing plant-based, in reality	Ground beetles and hedgehogs are the ones that regulate them

What does not work — and why it needs to be said

A single isolated pot on a terrace. Without foliage being brushed, diffusion is negligible.
A repellent plant two meters from the crop. Scent masking works over short distances. Two beds side by side have no effect; plants must be alternated within the row.
Rely on them against an established infestation. These mechanisms reduce pest pressure upstream; they do not treat infestations.
Expect them to prevent diseases. Downy mildew, powdery mildew, and rust are fungi: they arrive with wind and rain, indifferent to smells. Against them: spacing, ventilation, watering at the base, and mulching.
Plant extracts as miracle repellents. Nettle extract is an excellent growth stimulant, not an insecticide. Tansy decoction has a real but short-lived repellent effect, and it cannot distinguish an aphid from a ladybug.

The fundamental reason: an overabundance of pests mainly signals a lack of regulators. A garden that shelters ladybugs, hoverflies, ground beetles, hedgehogs, and tits regulates itself after two or three years — and no repellent plant can deliver that result.

Build a system that holds up

Three levels, from most effective to most supplementary.

Eliminate the causes — standing water for mosquitoes, excess nitrogen for aphids (tender, nitrogen-rich foliage attracts them), plants spaced too closely for diseases.
Install regulators — flowers with staggered blooming from March to October, wild areas, shelters. See Combining flowers with the vegetable garden.
Add repellent plants—as a complement, interspersed among the rows and within reach on the terrace.

In that order. Many gardeners start with the third point and are surprised that it is not enough.

Frequently asked questions

Is citronella really useful?

Its compounds are strongly repellent—they are used in commercial products. But the intact plant releases almost none of them. It becomes useful when you crush its leaves and rub them on your skin, with an effect lasting twenty to forty minutes.

Can you make your own repellents?

A concentrated infusion of lemon balm or lavender, cooled and sprayed, has a mild, short-lived effect. For topical use, essential oils require real precautions—dilution, contraindications, and allergies. Ask a pharmacist for advice rather than following a recipe found online.

Do these plants also keep pollinators away?

No, quite the opposite: lavender, lemon balm, savory, catnip, and mint are excellent bee-friendly plants when allowed to flower. Olfactory masking hinders the search for a specific host plant, not nectar collection.

Should repellent plants be pruned or left to flower?

Both, on different plants. The foliage is richer in essential oils before flowering, but the flowers feed beneficial insects. Keep a few plants for each purpose.

Does it work in a pot on a balcony?

For masking at the base of a crop, yes—a basil plant in a tomato container. For mosquitoes, the same rule applies as elsewhere: keep it within reach and crush it. See Balcony vegetable garden.

Key takeaway

A repellent plant releases almost nothing until it is crushed. To keep mosquitoes away, place it within reach—and above all, empty stagnant water. In the vegetable garden, masking works but only at close range, and it always comes a distant second to the real solution: feeding those that eat pests.

To go further

Discover our aromatic and medicinal seeds and our bee-friendly plants—the best allies for a self-regulating garden.