|Official Plant Name||Tropaeolum majus|
|Plant Type||Annual Flower / Climber|
|Native Area||South & Central America|
|Flowers||Commonly red, yellow or orange|
|When To Sow||March, April, May|
|Flowering Months||July, August, September, October|
Exposed or Sheltered
1.5 – 2.5M
1.5 – 2.5M
July – October
Chalk, loam, sand
Tropaeolum, commonly called Nasturtium, is a genus of climbing, sometimes creeping, plants that have fantastic ornamental value in terms of their heights and spreads, the foliage, and the flowers. These rather unusual plants typically have a very long blooming season, and their flowers come in an astonishing variety of colours from icy blue to blazing red. Try to grow charming Tropaeolum as perennials!
Tropaeolum hail from South and Central America and have been introduced to a motley assortment of countries spanning all continents and covering temperate, sub-tropical, and tropical zones. The plant’s given name, Tropaeolum, is usually restricted to formal use with the plant being known in the English-speaking world and even elsewhere by its common name ‘Nasturtium.’ It is not to be confused with Genus Nasturtium which encompasses Cress species.
Nasturtiums are unusual plants on several counts. Make that marvellously unusual plants. First, most of them are resilient, if not always strong, climbers though a few have a bushy, spreading habit. Second, their foliage is both uncommon and attractive. Third, their brilliant flowers are even more attractive; what’s more, they bloom for months on end. Fourth, they are very low-care plants. Fifth, — oh dear! There’s more but we don’t want to bore you neither do we want to appear as if we’re shilling for these (lovely!) floriferous climbers.
Genus Tropaeolum comprises between 85 to 95 species (all native to Central and South America). Taxonomically there is a connection to abovementioned Cress because both Genus Tropaeolum (‘Nasturtium’) and Genus Nasturtium (Cress) fall under Order Brassicales, many of whose members are edible and which have a tangy, peppery, or pungent flavour, with Mustard probably being the ‘Head of the Family.’ As it happens, that fifth attribute was going to say that Nasturtium flowers and leaves are edible and lend a piquant zing to salads and even soups. Out of Rocket? No prob if you have a Nasturtium in the garden.
Though Nasturtiums are deciduous perennials, in most regions of the United Kingdom they are half-hardy and are grown as annuals. However, along the south-western coast and a few other regions several varieties can be grown as the perennials that they are (though a few varieties, such as Tropaeolum tuberosum and Tropaeolum speciosum, can be grown as perennials in almost all regions of the U.K.). If you are lucky enough to call a relatively balmy region home, you can bring great joy to your garden by growing arguably the most ornamental of all climbers.
To begin with, the foliage is of a mellow sea-green colour. The leaves are decorative in their own right, being either lobed, often deeply, or rounded and shield-shaped. The showy flowers come in hues of yellow, orange and red, but a few are in shades of blue and purple and some are also bi-coloured or variegated. Most are funnel-shaped but even here there is variety as a few are salver-shaped. What they have in common is a very distinctive spur behind or beneath. To top it all off, Nasturtiums bloom for months on end, many varieties are fragrant, and the flowers attract butterflies and hummingbirds!
Background and Origins
Native to all of South America, except Brazil, and Central America, T. tuberosum was known to the Incas and other indigenous peoples who cultivated it for its edible tubers. Other varieties’ leaves and flowers were also consumed, as we know from missionaries’ diaries.
Tropaeolum entered the Old World through Spain where T. minus was introduced in the Sixteenth Century by Nicolas Monardes, a herbalist and physician from Seville. By the 1590s T. minus had arrived in Great Britain. Later, T. majus came from Peru to the Netherlands in the late Seventeenth Century. It is about this time that Tropaeolum cultivation took off in Europe, including Great Britain, though at that time it was primarily viewed as an edible salad plant and as a medicinal herb. In Great Britain Nasturtiums gained popularity during the Victorian Era when the flowers were frequently seen in vases and bouquets, at which time the plant began to perceived as an ornamental.
The name Tropaeolum derives from the Latin word tropaeum which is a monument dedicated to a victory in battle. The vanquished soldiers’ helmets and shields used to be hung from or placed under the tropaeum. The English word trophy also derives from Latin tropaeum. As many varieties’ funnel-shaped flowers resemble helmets – witness those of T. leptophyllum – and just as many varieties’ entire leaves resemble shields, Tropaeolum is like a living tropaeum!
From among the many species and cultivars of Tropaeolum we present a Top Ten list underneath of our favourite varieties, which also turns out to be a fairly diverse and representative selection.
T. minus or Dwarf Nasturtium is the species that ‘started it all’ in Europe. It is native to Ecuador and Peru, growing at altitude. A trailing, dwarf species, it grows to but 30 centimetres with a spread only marginally bigger. It blooms from mid-summer to early autumn. The small, funnel-shaped flowers are a buttercup yellow with darker amber-to-red splotches.
T. majus or Garden Nasturtium is native to a swath of land from Colombia to Bolivia. It has a height and spread of 2 to 2.5 metres. It too blooms from mid-summer to early autumn. It has open, disk-shaped flowers in deep, rich tones of yellow, orange, and red with sizes ranging from 3 to nearly 6 centimetres. It is the parent species of some of the most widely-available and popular varieties.
T. minus ‘Ladybird’ is a cultivar of T. minus and is even shorter at only 20 centimetres. The leaves are very much shield-shaped and the flowers are a cheery yellow with brilliant red ‘ladybird’ spots at the proximal end of each petal. It blooms from early summer into autumn.
T. minus ‘Black Velvet’ may not bear actual black flowers but they do have a very dark flush and the deep creases in the petals also create shadows on the flowers whose colour varies from blood red to mahogany. They have a bright yellow centre. This bushy variety is about 30 centimetres high with a similar spread. It blooms from mid-summer into autumn.
T. majus ‘Chameleon’, a cultivar of T. majus, is also a bushy variety with a height and spread of about 30 centimetres. Its leaves are nearly round. It produces particularly eye-catching flowers. Salver shaped, they are of a pale yellow colour with large red-to-crimson ‘splatters’ on each petal. As the flower matures it undergoes a chameleon-like colour-shift from yellow to light pink! It blooms from mid-summer into autumn.
T. majus ‘Empress of India’ is an old heirloom variety. It has a bushy habit with a height and spread of 35 to 40 centimetres. It features wonderfully rounded sea-green leaves. The funnel-shaped flowers range in hue from vermilion through scarlet to crimson, and sometimes develop a purple flush. It blooms from mid-summer into autumn. A superb choice for patios and planters.
T. speciosum or Flame Nasturtium comes from the highlands of Chile and it is well known to grow strongly in the highlands of Scotland, as one of the hardiest varieties, rated to Zone H5. It is of a climbing type and reaches heights from 3 to 4 metres. The star-shaped flowers are about 2 centimetres across and, as its name suggests, are of a fiery orange colour. These have especially prominent spurs. R.H.S. Award of Garden Merit.
T. azureum or Blue Nasturtium is also from Chile but this one is not frost-hardy. It is of the less-common summer-dormant type that retains its foliage from autumn through winter into spring, which would lend fantastic colour to the garden because its leaves are of a light, bright green and are palmately lobed. It grows to only about 1 metre. A short flowering season in spring yields delightful flowers. They are disk- or salver-shaped, are of a gentle lilac-to-purple hue with a cream centre.
T. peregrinum or Canary Creeper hails from Peru and is a very popular variety in the United States. ‘Canary Creeper’ at one and the same time is a misnomer and is also very apt. This plant is very much of the climbing type; what’s more, it grows to about 3 metres and can even reach 4 metres. However, the flowers are a perfect canary yellow and they even bring to mind canary wings, thanks to the narrow, fringed, ‘fluttering’ petals! The deeply lobed leaves are of a rich green hue.
T. tricolor or Three-Coloured Nasturtium surely boasts one of the most uncommon and gorgeous flowers. It is also uncommon as a summer-dormant species. T. tricolor is native to Chile and is a climber, reaching heights of 1 to 1.5 metre. The pinnately lobed leaves are of a rich green shade. As for the small but outrageous blooms, they actually comprise of a pronounced calyx enclosing the flower. The flower is yellow, often with greenish edging, and the calyx is orange-red with purple-to-crimson edging. This species even boasts a long blooming season that lasts from mid-winter to early summer. R.H.S. Award of Garden Merit.
Other recommended varieties include T. majus ‘Hermine Grashoff’, T. majus Alaska Series, T. majus Whirlybird Series, T. majus ‘Milkmaid’, T. majus ‘Jewel Cherry Rose’, T. tuberosum, T. polyphyllum, T. leptophyllum, T. hookerianum, and T austropurpureum.
Habitat and Growing Conditions
Tropaeolum grow in the wild from south-eastern Mexico and Guatemala in the north to the tip of Patagonia in the south, excluding Brazil. Some species grow at altitude in the alpine regions of the Andes while others grow in lowland coastal areas. Chile is a particular centre of species diversity.
What is common to all of them is that they are indifferent to soil as the grow in soils ranging from average down to what can only be called very poor. They are usually found growing in full sun.
Though their water needs are low they do best in moist soil.
The vast majority of Nasturtium species are frost-tender and are hardy (only) to Zone H3. A few species, though, are frost-hardy down to Zone H5.
Where to Plant Nasturtiums
Most Nasturtiums are climbers that attain heights of about 3 metres. A few, such as T. speciosum and T. peregrinum, can reach heights of up to 4 metres. An overgrown Nasturtium climber along the wall of a house will impart a charming, country-cottage effect to your urban dwelling. They will produce the same countryside charm when they climb up and wash over boundary walls and fences with next to no training.
The shorter, more delicate, Nasturtiums, for example T. azureum, are ideal to plant beside summer-houses, especially when the walls are of latticework – then a few flowers and leaves will ‘peek’ inside.
Some Nasturtiums have a spreading, bushy habit. Examples include T. majus ‘Empress of India’ and T. majus ‘Chameleon.’ If grown in large planters these species will add great colour and produce a delightful billowing effect by the patio or on the porch. They can actually be used to create borders as well.
Feeding, Care and Growing Tips
Most, if not all, Tropaeolum varieties can be grown reliably from (the rather large) seeds. One may as well add that they will just as reliably start to wilt and wither if transplanted. Therefore, do not start these plants in pots for later transplanting though you may very much grow and keep short and spreading varieties in planters.
The best time to sow Nasturtium seeds is late spring because higher soil temperature plays a big part in the germination of the seeds.
These plants should be sited in a full sun location though partial sun will work well too.
Push seeds 1 to 2 centimetres into moist soil and water them. Before sowing seeds you may keep them in a little water or wrap them in wetted paper towels or tissue paper for 24 hours to get them going.
Besides being very transplanation-averse, these plants have yet another quirk. They do best in poor soil! The richer the soil, the more foliage they will produce at the expense of flowers. A mix of gravel, chalk, and sand with but a sprinkling of humus or manure mixed in will be perfect though any old soil will do.
Soil pH hovering around neutral is ideal though any pH from Moderately Acidic to Slightly Alkaline will do fine for most Tropaeolum varieties.
The one non-negotiable is that soil should drain very well.
These plants should get be watered about twice a week, be it from the rains or the hosepipe. When the soil dries out, it is time to water them. Younger plants need more regular watering than established outdoor ones.
Avoid fertilizing Nasturtiums of any kind. Nitrogen-high fertilizer especially should be avoided because it will spur growth of foliage on an already leafy plant; in turn, this will negatively affect the number and size of blooms. Indeed, even a balanced fertilizer would not be a smart idea for Nasturtiums under most circumstances.
If you have grown a Nasturtium as a perennial in the United Kingdom, then, if it is of a type that is dormant in winter and is not frost-hardy (the majority of varieties), soon after the leaves have shed in autumn spread a layer of leaf mulch on the soil above the root system. Remove it a couple of weeks after the last frost of winter.
In general Nasturtiums do not need to be pruned as they are deciduous plants (assuming you can grow them as perennials and not as annuals).
In general, the bushy spreading varieties may be cut back soon after the flowering season is over. Climbing varieties can be deadheaded to encourage fresh blooms.
Don’t get caught out by the flowering season and dormancy season of your Nasturtium variety; keep in mind that T. azureum, T austropurpureum, and T. tricolor are all dormant during the summer and bloom in winter and spring.
Common Diseases and Problems
Tropaeolum is an inherently healthy genus and is known to stay free of disease but the different varieties have varying susceptibilities to pests. In general, the shorter Chilean climbers are the most robust while T. majus and its varieties are the least robust.
Both T. speciosum and T. peregrinum may be attacked by flea beetles and caterpillars with the former also a target for blackfly and the latter for aphids.
T. majus and its cultivars are susceptible to blackfly, flea beetles, and caterpillars, in addition to which a lesser threat is posed by slugs.
Where to Buy Nasturtiums
Nasturtium seeds of the spreading, trailing varieties, are widely available at nurseries and online stores. In addition, seeds of the more popular climbers, for example T. speciosum, are just as freely found. Some, such as T. majus ‘Chameleon’, are much harder to find.
Because species of this genus do not take well at all to transplanting, only a few varieties, such as the bushy, spreading varieties, are available as plants in containers from a limited number of garden centres.
If you already have a Nasturtium, you may be able to get new Nasturtiums for yourself and your friends.
Some species self-seed very reliably. You could also simply let the flowers wither and then harvest the seed pods.
T. azureum and T. speciosum can be propagated by division though this is not recommended and you must take great care not to disturb the parent plant. The divided plant may or may not take. It is much easier to get ‘new’ T. majus varieties as most of them can be propagated from stem cuttings.
Kersie learnt the basics of gardening as a toddler, courtesy of his grandfather. In his youth he was an active gardener with a preference for flowering plants. He is a professional and vocational writer and his freelance projects have spanned various kinds of writing.