Tropaeolum majus Seeds | Nasturtium
LATIN NAME: Tropaeolum majus
COMMON NAME: Nasturtium
Plant Profile
When Linnaeus named this plant Tropaeolum, he was looking at a battlefield image: to his eye, the round leaves hung like the shields and the spurred flowers like the blood-stained helmets nailed to a Roman victory trophy, a tropaion. No other garden annual carries a name invented from military scenery, and once you see the shield-and-helmet picture, the trailing mass of green discs and flaming blooms never quite looks like ordinary foliage again.
The leaves are peltate, meaning the stalk joins the blade at its centre rather than its edge, so rain rolls off a tilted green umbrella and beadlike droplets sit on the surface. Each funnel-shaped flower carries five petals and a calyx drawn out into a long hollow spur packed with nectar, a design aimed at long-tongued bumblebees. Charles Darwin himself studied the climbing movements of this genus, recording how the leaf-stalks twist and grip in his book on climbing plants.
Spanish explorers carried the plant back from the Andes in the sixteenth century, and monastery and kitchen gardens grew it under the name Indian cress, for the peppery cress-like bite of its leaves. From those beds it escaped into the wider European garden and became, within a couple of centuries, one of the most widely sown annuals on the continent.
Gardeners also deploy nasturtium as a deliberate sacrifice. Colonies of black aphids find it irresistible, so a row planted beside beans draws the infestation onto leaves you can simply strip and bin. It is companion planting with an honest purpose: the plant suffers, the beans stay cleaner, and the hoverflies that hunt the aphid colony arrive in numbers.
Science & Biotechnology
The sting on the tongue is chemistry, not capsaicin. Nasturtium tissues store a glucosinolate called glucotropaeolin, which the enzyme myrosinase converts, the instant a leaf is chewed or crushed, into benzyl isothiocyanate. That same pungent compound has drawn serious attention from agricultural scientists, who trial nasturtium plantings as a biofumigant crop and as a host plant for beneficial insects in orchard floors.
Uses & Benefits
Analyses of the orange and yellow blooms keep finding some of the highest natural lutein concentrations recorded in flower tissue, which is why petal extracts have been examined as a pigment and colourant source. It is a pleasing reversal: the same petals that brighten a salad plate carry one of the plant world’s richest loads of this carotenoid.
Three separate harvests come off one plant. The leaves give a watercress heat to sandwiches, the flowers bring colour and mild spice to salads and flavoured vinegar, and the tripartite green seed pods, picked young and dropped in spiced brine, become the classic poor man’s capers, a substitute for the Mediterranean bud that costs nothing but patience.
Growing from Seed
The seeds are the size of dried peas and easy to handle: push each one about 2 cm deep into warmed soil after the last frost, water once, and let the fleshy seedlings take over. This is the rare annual that flowers best on hardship. Rich soil and nitrogen feed produce a wall of leaves and few blooms, while a poor, dry, well-drained spot gives the long-spurred flowers you planted it for.
Climbing strains will scramble 2 m up a fence, trellis or old apple tree if given strings to grip, while compact dwarf strains carpet the front of a bed and spill from window boxes. Neither type needs deadheading; spent blooms drop cleanly, and the plant simply keeps producing them until the first hard frost cuts the season off.
Water new sowings until roots take hold, then leave the plant to fend for itself; nasturtium is built for dry summers and rots easily in damp shade. A light trim of sprawling stems keeps a path clear without harming the flow of bloom. Seed saving is the easiest of any annual: the tripartite pods ripen from green to straw, drop onto bare ground and overwinter there without protection, so a single untidy corner guarantees next year’s crop. In frost-free pockets the plant can even carry through winter and bloom again, behaving as a short-lived perennial.
Our Take
If you like the peppery salad angle, sow it alongside arugula and the blue-flowered borage, both equally happy in a rough sunny corner. For a window box of comparable vintage and ease, the Victorian favourite balsam impatiens is a good partner. Keep a few of the early pods unpickled and let them dry on the plant: the fat seeds store through winter in a paper envelope and will still be fat and willing next spring.
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