Ornamental · Tropaeolaceae
Nasturtium
Tropaeolum majus
Give it poor soil and full sun, and the nasturtium answers with peppery leaves and bright, edible flowers all summer.
Full sun
50–86°F · 10–30°C
35–50 days
USDA 2–11
Overview
Nasturtium is a fast annual built around round leaves and warm-toned flowers. The leaves are near-circular and smooth, each held out on a slender stalk, and the blooms open in warm hues that carry the plant's cottage-garden reputation. Break a leaf or a petal and the same fresh, watercress-like bite runs through both, which is why the greens and flowers land in salads and on the plate.
The plant grows fast and shapes itself to the type, some stems climbing, some trailing along the ground, others staying low in a rounded mound. It does its best work in lean, poor soil, where a hungry plant throws up flowers instead of leaf. Feed it or set it in rich ground and the round foliage crowds out the color.
Up close, the plant is a magnet for small insects. Aphids and cabbage caterpillars cling to its stems and leaf undersides, and gardeners turn that pull into a trap crop that draws those pests off nearby vegetables.
Care
The short version: full sun and lean, well-drained soil with no fertilizer. Water enough to keep the young round leaves plump, then let established plants dry a little between drinks, and press the seeds straight into the ground where they will grow rather than transplanting.
Light
The round leaves and warm flowers color up fullest in full sun. In part shade the plant leans toward soft green foliage and fewer blooms, so the brightest spot brings out the most flower.
Water
Keep the soil lightly and evenly moist while the young round leaves are still filling out. Once the plant settles into lean, well-drained ground, it takes short dry spells without wilting, so let the top inch dry before the next drink. Waterlogged soil is the one thing it will not stand.
Soil
The plant thrives on neglect. Set it in lean, well-drained loam or sandy soil of poor to average fertility and skip the rich compost. Fed too well, it piles up round leaves and holds back its flowers.
Temperature
Nasturtiums grow between 50°F and 86°F (10°C to 30°C). The soft green stems are tender and carry no frost tolerance, so sowing waits out the cold, and the plant collapses at the first hard frost.
Humidity
Ordinary outdoor air suits the foliage, with no number to hit. Good airflow around the leaves counts for more than moisture in the air, since dense growth invites the aphids that already cluster on this plant.
Feeding
The plant wants no feeding. It flowers hardest in hungry soil, and nitrogen-rich fertilizer swells the round leaves while the blooms all but disappear.
Pruning
Upkeep is mostly deadheading. Pinching off the faded, curling flowers keeps fresh buds opening, and any damaged or diseased leaf comes away as it shows.
Size & spacing
Plants stretch from 12 inches (30 cm) on the low bushy dwarfs to 10 feet (3 m) of trailing stem on the climbers, so the form sets the space. Let the trailing kinds spread across the ground and give the tall stems something to grip and climb.
When to plant
Nasturtiums grow fast, and their soft green stems have no defense against frost. The big seeds go into warm soil once the spring frost has passed, and the warm-toned flowers open from early summer until the first fall frost.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Optional, 2 to 4 weeks before the last spring frost in biodegradable pots; resents root disturbance.
- Plant: Direct sow after the last spring frost once soil has warmed; dislikes transplanting.
- Harvest: Blooms early summer until the first fall frost.
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most nasturtium trouble reads right off the plant: tiny insects clustered on the leaves, or a mound of round foliage with the flowers missing. Both are easy to see once you know the look. Match what you find below, then act before it spreads.
Sticky leaves and crowds of tiny insects on the shoot tips
The shoot tips crawl with aphids, tiny soft-bodied specks of green or black massed along the stems and under the round leaves, with a sticky honeydew film and edges that curl inward. This crowding is no accident, since nasturtium pulls aphids in like little else and stands in as a trap crop because of it. A hard jet of water sweeps the clusters off, a few can be left on a plant guarding the vegetables nearby, and a plant buried under them comes out with insecticidal soap on the worst leaves.
Fix:
- Hose off colonies with a strong jet of water
- Tolerate moderate numbers when used intentionally as an aphid trap crop and remove the worst-infested plants
- Apply insecticidal soap to heavily infested foliage if needed
Ragged holes chewed through the leaves
The round leaves show ragged, torn holes, and the culprits are cabbageworms and cabbage loopers, plump green caterpillars from the cabbage white butterfly. Their green bodies lie flat against the matching leaf and vanish, so a close look turns them up along with their dark specks of droppings, ready to be picked off by hand. Set beside brassicas, a nasturtium gathers these chewers onto its own foliage, and Bt clears any leaf stripped down to the veins.
Fix:
- Handpick caterpillars
- Use as a companion trap to draw cabbage pests away from nearby brassicas
- Apply Bacillus thuringiensis (Bt) to heavily fed foliage if needed
Plenty of leaves but hardly any flowers
A dense mound of round green leaves rises with barely a bloom breaking through, and the reason is soil that is too rich. Kept a little hungry, a nasturtium spends itself on flowers, but fertile ground or any feeding pushes all that energy into leaf. Cut the fertilizer and grow it in lean, well-drained soil in full sun, and the warm-toned flowers rise back up through the foliage.
Fix:
- Stop fertilizing
- Grow in lean, well-drained soil in full sun
Toxicity
For households with pets, the leaves and flowers hold no danger: nasturtium is safe all round. The ASPCA lists it as non-toxic to cats, dogs, and horses, and the round leaves and bright flowers are edible for people, with a peppery flavor. Nothing on the plant needs to be kept from curious animals or children.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The ASPCA lists garden nasturtium as non-toxic to cats, so a curious bite from a round leaf or a bright petal does no harm.
Dogs None
Dogs are unharmed by the leaves and flowers. A chewed piece does nothing, though a large mouthful of any plant can loosen the stomach.
Horses None
Horses can graze the soft green foliage safely, since the ASPCA rates nasturtium non-toxic to them.
Rabbits Safe
The peppery round leaves and warm-toned flowers are safe for rabbits, and many nibble the tender foliage as a fresh treat.
Livestock Safe
Grazing animals take the leafy growth without harm, so a plant within reach of the paddock is no danger.
Birds Safe
Backyard birds and chickens peck the leaves and the big round seeds safely, with no toxic parts among them.
People Safe
The round leaves and warm-toned flowers are edible, carrying a bright, peppery bite that stands out in a salad. The young green seed pods can be pickled like capers.
Varieties
Nasturtiums range from long-stemmed trailing climbers to low bushy dwarfs, with flowers coloring from soft cream through to deep scarlet. These are the ones worth knowing by name.
Alaska
A compact, bushy type whose round leaves are marbled and streaked with cream, prized as much for that variegation as for the flowers.
Empress of India
A compact plant that sets deep crimson-scarlet flowers against unusually dark blue-green leaves.
Jewel
A mounding dwarf whose semi-double to double flowers carry extra layers of petals on tidy, bushy plants.
Climbing/Tall single
A vigorous trailing or climbing form whose stems stretch to about 10 feet (3 m), long enough to clamber over fences and trellises.
Companions
Nasturtiums earn their place beside vegetables by drawing pests onto themselves and away from the crop, which makes them a useful neighbor for brassicas and squash alike.
Plant near
Cabbage and other brassicas: Used as a companion and trap crop; nasturtium helped reduce imported cabbageworm and cabbage looper damage in broccoli and cabbage.
Squash and other cucurbits: Interplanting nasturtium helped reduce squash bug and cucumber beetle damage in squash and pumpkin.
How to propagate
Nasturtiums start easily from seed, and those big, round, pea-sized seeds and their quick germination make them a satisfying first sowing for a new grower.
SeedEasy
Direct sow after the last spring frost once soil is warm. · Germinates in about 7 to 14 days; blooms within roughly 5 to 7 weeks.
The seeds are big and round, roughly the size of a pea, with a wrinkled, hard coat that an overnight soak swells and softens. Press them straight into their final spot once the spring frost has passed and the soil has warmed, since the plant resents any tug at its roots and rarely transplants well. Green seedlings push up in 7 to 14 days, and the first flowers unfurl within about 5 to 7 weeks. For an earlier start, sow into biodegradable pots that sink into the ground whole.
Myths
Nasturtium is poisonous to cats and dogs.
The ASPCA lists garden nasturtium as non-toxic to cats, dogs, and horses, and the round leaves and warm-toned flowers are edible for people too. The old scare belongs to watercress, an unrelated plant that carries the botanical name Nasturtium officinale. Tropaeolum majus is safe to grow around pets.
Nasturtiums repel aphids and keep them out of the garden.
The truth runs the other way. A nasturtium attracts aphids rather than repelling them, drawing those tiny soft-bodied clusters onto its own stems and leaves, which is the whole point of using it as a trap crop. Planted near vegetables, it collects aphids and some caterpillars onto itself and off the plants you want to protect.