Calgary Horticultural Society: Nasturtiums are a multi-purpose beauty

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I fell in love with jewel-coloured nasturtiums after someone dared me to eat one of the flowers. Very dubiously, I picked a lovely, brilliant red one, took a tiny bite and experienced the terrific peppery taste of it. The rest of it followed that first nibble, and I have been munching happily on nasturtium flowers and leaves and pickling their green seeds as capers ever since.  

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Nasturtium, from Latin, means “nose-twister,” an obvious reference to the pungent smell and taste of the edible parts of this most beautiful flowering herb that hails from the Andes region of South America, where species are weakly perennial or annual creepers. It belongs to the small Tropaeolum genus, which contains just 80 species, ranging from herbaceous perennial to annual. Nasturtium has several common names, such as Indian cress and canary flower. Indeed, the leaves are often used in many cultures instead of watercress or peppercress. This is interesting, as the watercress’s scientific name is Nasturtium officinale, but it actually belongs to the Brassicaceae, or cabbage, family.  

Brought from the New World to Europe in the late 16th century, nasturtium was named by Linnaeus as Tropaeolum, after an ancient Roman custom of erecting a tropaeum (trophy pole) after battle, from which were hung the fallen warriors’ helmets and shields. The flowers and leaves of this new plant reminded him of that armour. Since then, members of the Tropaeolum genus have symbolized victory in battle, conquest and patriotism, which are also embodied in the Incan belief that the scent of the flowers gave vigour, vitality, and the power to face their enemies!  

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Nasturtiums have rounded, bright green, smooth leaves, 5-12 cm in diameter, borne on slender petioles. The 2.5- to 5-cm single flowers have five petals in a range of colours, from rust to orange to brilliant red and golden yellow; some are nearly pink. Surrounding the petals are five sepals, united to form a prominent calyx, with one sepal modified to be a nectar-bearing spur.  

The nasturtiums we love to plant in containers and borders are either Tropaeolum minor or Tropaeolum majus or are hybrids of both species. The difference between them is that T. minor has a twining and trailing habit and T. majus a mounded or bushy habit of growth, which can make a real difference, depending on whether you want to use them in hanging baskets, in containers, in raised beds or along borders. They are often classified by their habit of growth into dwarf, semi-trailing, and climbing. Plant them with your other edibles, especially Brassica species, tomatoes, and cucumbers, as they are a magnificent trap crop for aphids, which choose them over just about anything else. Once they are covered with aphids, simply prune off the infested parts or wash the bugs away with water.  

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Easily propagated from seed, either directly in the ground once the soil has warmed up in spring or indoors, these seedlings grow very quickly to form sizable plants in no time at all. Whether you are planting containers or beds, ensure that the soil is not too rich. Nasturtiums prefer lean, slightly acidic and very well-drained soil, similar to that of their native habitat. They are a sun-loving plant – for lots of flowers throughout the summer, make sure they have six to eight hours of sun. Should they not get enough sun or have too many nutrients, they will have mainly leaves but not many flowers. Do deadhead regularly to ensure the plants keep flowering, and pickle the tender green immature seeds to use as “poor man’s capers,” first making sure, of course, that you harvest lots of flowers for salads, garnishes, and snacks.  

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As summer wanes, leave the seeds on the plants to mature until they are brown and dry, gathering them just before they might fall to the ground. Store them inside in a cool, dry place to sow again next year.  

There are many nasturtiums to choose from, with heirloom varieties represented by Trapaeolum being Empress of India, Globe of Fire, Yeti, Peach Melba or Salmon Baby with its semi-double blooms. I love the Alaska series with its variegated leaves, but also plant Jewel Mix, especially the Double Dwarf Jewel Mix. But Whirlybird and the lovely Gleam series cannot be ignored, either.  

There really is no reason not to include at least a few nasturtiums in your garden every year, whether you choose them for being easy to grow or for their beautiful flowers, or you grow them as edibles or as a companion plant. Just try them, and munch away!