Bored with everyday Nasturtium? Hello Rare Tropaeolum species.

by Matt Mattus | Posted on

NOW THAT THE HURRICANE IS OVER, HOW APPROPRIATE THAT THIS TROPAEOLIUM NOW BLOOMS – A FLAMING PHOENIX RISING, WITH ITS BRILLIANT YET SMALL SOUTH AMERICAN NATIVE, TROPAEOLUM SMITHII, IS A RARELY GROWN SPECIES WITH A BRIGHT FLOWER.  IT IS ‘GROWABLE’ AS AN ANNUAL FOR THE SUMMER GARDEN OR IN CONTAINERS, IF YOU CAN FIND THE SEED. ( TRY CHILTERN SEEDS IN THE UK).

 Last February I wrote a post about plants that are on my ‘wish list’, various rare or rarely seen genus or species, a list that included some rare nasturtiums (Tropaeolum species), particularly Tropaeolum moritzianum. I never found a source for that particular species, but I did receive a gift from the botanical site specializing on the genus Tropaeolum that I referenced in that post,  site  so thanks to John McFarlane I have these species blooming today, after the Hurricane. Meet Tropaeolum smithii and T. argentinum, both rarely found in collections. He shared some cultural information that challenged me, since he stated that both of these species are difficult to germinate, which of course, only made me more up to the challenge.
TROPAEOLUM ARGENTINUM, A BIT MORE REFINED AND DARE I SAY, A LITTLE ORCHID-ISH? THIS AIN’T YOU”RE AVERAGE CANARY VINE
 We are all familiar with the more common Nasturtium majus, yes, those bright orange and yellow flowers found in edible flower packets and the annual with large seeds and tiny water-lily shaped leaves that are also edible and peppery flavored, often grown by children and new gardeners due to their high performance level. Easy, attractive and a long blooming season makes these annuals some of the best for filling annual borders, but these species forms are a bit more precious – they will do best if grown in containers and allowed to scramble over low shrubs, as they grow in the wild.
EARLIER THIS SUMMER, YOU CAN SEE HOW SIMILAR THE FOLIAGE ON THIS T. SMITHII LOOKS TO THE GEOPHYTIC SPECIES, THE ONES THAT GROW FROM TUBERS THAT YOU CAN SEE IN MANY OF MY WINTER POSTS. THESE APPEAR TO BE A BIT MORE STURDIER, BUT JUST AS CHALLENGING TO GERMINATE, THE TRICK, IF ANY, APPEARS TO BE HOW TO KEEP JUST ENOUGH MOISTURE AROUND THE SEED WITHOUT CAUSING ROT. 
T. SMITHII GREW ON A SMALL TRELLIS IN A CONTAINER THAT I SET NEAR THE GREENHOUSE DOOR, IN A LARGE BAY LAUREL TUB.  IT  OUT-GREW THIS POT, CHOOSING TO REACH OVER TO A NEARBY SHRUB WHERE IT COULD TUMBLE AND GROW OVER.
T.SMITHII SEEMS MORE NATURAL AND IN CHARACTER ONCE IT ESCAPES ITS POT. THE TINY 3/4 INCH BLOSSOMS ARE ATTRACTIVE AND BRIGHT, LIKE ELF CAPS, BUT COLORED AS IF THEY ARE ON FIRE, A TONE DIFFICULT TO CAPTURE ON A DIGITAL CAMERA.
THE TROPAEOLUM ARGENTINUM  SEEDLING WAS PLANTED, AS AN EXPERIMENT SINCE I FOUND VERY LITTLE CULTURAL INFORMATION FOR IT) IN AN ALPINE TROUGH, SINCE IT WAS FAST DRAINING. IN JUNE, THE SEEDLING HAD ONLY A THIN, WIREY STEM WITH A COUPLE OF SAD LEAVES. THE BLOSSOMS ALMOST BECOME LOST IN THE SLIGHTLY YELLOWING FOLIAGE. UP CLOSE? VERY PRETTY.
I DON”T KNOW WHAT I WAS THINKING PLANTING THIS IN A TROUGH, BUT IN LATE JULY, THIS SPECIES TOO, TOOK OFF, ALMOST CONSUMING THE ROUND TROUGH. IF I GET SEED, I WILL FIND A BETTER PLACE TO GROW THIS. FOR NOW, I ALLOWED IT TO TUMBLE OVER SOME TWIGS FROM A NEARBY CRAMBE CORDIFOLIA SEED STALK, WHICH I PROVIDED AS A TEMPORARY TRELLIS.

For information on other Tropaeolum species that I have grown over the past year, check out these posts from the winter, since this is the month when you can order and plant the tubers of these other South American species. I suggest Tropaeolum tricolor

Tropaeolum tricolor, a tuberous species that can be grown as a winter-flowering plant for a cold windowsill or cold greenhouse. It grows from a small, potato-like tuber – order them now from finer bulb sources.


Tropaeolum azureum is more challenging to grow, but I did have spectacular luck with the tuber three years ago – patience is required, as the tuber can be fussy, often sitting dormant for many years before deciding to grow. It’s been sitting dormant again in the dry, hot protection of the greenhouse for two years now….maybe this winter?

TROPAEOLUM X TENUIROSTRE  is even more rare, a cross which is naturally occuring in Chile. Another tuberous Tropaeolum worth growing if you are thinking about collecting this enticing genus, which few seem to collect. Here is a story about this species blooming in my greenhouse this past spring. Another wirey vine, the branch is a piece of a Japanese Maple that I cut and used as a support branch.

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  2. I received these seeds from a collector in the UK, but you can sometimes find them at Chiltern Seeds in England ( they are currently sold out). ANother source I like for the tuberous species is Paul Christian Rare Bulbs in England. Both ship to the US and worldwide.

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