Tropaeolum majus Seeds | Climbing Nasturtium
LATIN NAME: Tropaeolum majus
COMMON NAME: Climbing Nasturtium
Plant Profile
Nasturtium is built around two shapes. The leaves are round, shield-like and long-stalked, sitting flat on the stem at the centre of the blade rather than at the edge, and each flower carries a backward spur behind the petals that hides a drop of nectar. The name itself comes from the Latin for “nose twist”, a joke about the peppery hit that hits the face on the first bite, and the spur is the part a child finds first when they pull a flower apart.
The round leaf is not only decorative. Its waxy surface sheds water and its long stalk lets it ride above the soil, so the plant stays clean even in a damp corner, and the same leaf makes a neat cup for a drop of rain or a sprinkle of dressing in the kitchen.
The plant is a trailing or climbing annual that scrambles by twining leaf stalks rather than true tendrils, reaching a metre or more across a support. In poor soil it flowers harder, which is why a rich bed gives more leaf than bloom, and a tuberous-rooted form stores energy underground for a second season in frost-free places. The species is diploid at 2n = 28.
The peppery flavour is not a true pepper at all but the result of mustard-oil chemistry. Crushing the leaf or flower releases it, and the sensation is close enough to watercress that the plant was once called Indian cress and eaten as a salad green on long sea voyages, when fresh greens were scarce and scurvy a constant threat.
Science & Biotechnology
Nasturtium belongs to a small family that runs the same glucosinolate defence system as cabbage and mustard, which is why the bite is so convincingly pepper-like.
The tissues hold glucotropaeolin, a glucosinolate that, when the leaf is damaged, breaks down through the enzyme myrosinase to release benzyl isothiocyanate, the compound behind the sharp, mustard-like bite. This is the same chemical class that gives the plant its place among edible ornamentals, and the reason the seed pods pickle into a credible caper substitute.
Because the stems are fleshy and quick to callus, Tropaeolum majus is a handy subject for shoot-regeneration studies, and nodal culture gives clean stock of selected double or compact forms without the variability of open-pollinated seed. A researcher can turn one cutting into a tray of identical plantlets in a few weeks.
Uses & Benefits
The whole plant moved from the Andes to European tables in the 16th century and has stayed there as a salad and garnish, prized as much for colour as for the bite.
The young leaves, the spurred flowers and the green seeds are all eaten; the flowers colour a summer salad and the seed pods are pickled like capers. The leaves are a useful source of vitamin C, which is why sailors once grew the plant against scurvy, and the blooms still turn up candied on a winter cake.
Growing from Seed
Nasturtium hates being moved, so the kindest method is to sow it where it will grow and let the trailing stems find their own way across the bed.
Push the large, wrinkled seed just below the surface of a lean, free-draining soil in a warm spot and keep it lightly moist; the round leaves appear quickly once the soil stays warm. Soaking the seed for a short while before sowing speeds a stand that is otherwise slow to break its hard coat.
Thin or set plants so each has 25 to 30 cm of room once they show several true leaves, because the trailing stems need space to spill or climb without smothering neighbours. A pot needs only one or two plants to fill, while a border row wants them spaced for air.
The plant reached Europe in the late 1500s and was taken up at once as a salad herb, the flowers and leaves eaten for their bite and the seeds pickled as a caper stand-in. Its vitamin C content made it a useful fresh green on long voyages, which is how a Peruvian climber became a staple of the European kitchen garden within a century of its arrival.
Our Take
I sow nasturtium straight into a trough by the step so I can grab a peppery leaf for lunch, and I let it climb the obelisk behind it. For other edible, scented climbers and flowers, the sweet pea at Lathyrus odoratus and the heartsease at Viola tricolor suit the same informal style, with the spider flower at Cleome spinosa for height behind.
Related Reading
More species in the same orbit as Climbing Nasturtium: