March 28, 2011

Never a plant as clever as magical Mr. Ornithophily

Aside from the familiar Nasturtiums of cottage gardens and window boxes, the genus Tropaeolum does present some hidden jewels known only amongst the elite plantmen and perhaps the geekiest of garden bloggers. A few of these tuberous forms are sometimes available from specialty bulb catalogs, with the most commonly offered being the beautiful Tropaeolum tricolor - a form with tubular blossoms, and dainty foliage, rarely found in the home garden. I encourage you to try growing this or any of the handful of other tuber ‘Tropes’ Yes, in many ways, these are the potatoes of the nasturtium family.

Destined never to become popular, I have seen more articles about the tuberous species in past few months.  In the most recent issue of the fine botanic journal - Curtis’s Botanical Magazine, a monograph has been dedicated entirely to these natives of the Andes mountains ( March 2011). As high-brow as some of the journals can be, this issue is particularly curious for me, especially as it focuses on some strange inter-specific habits these plants have with the bird species in Chile. 

Many tuberous nasturtium exhibit  ‘ornithophily’ - which describes a special relationship which some plants have between certain birds, which form a dependency to their nectar. Some tuberous, high-elevation species of tropaeolum share this unique relationship with two species of hummingbirds - a relationship so codependent, that some scientists are arguing that the plant and these two bird species, may have evolved together.

The tuberous nasturtiums of South America are quite collectable, and a few are available from rare bulb sources. I have grown five species, and two sub species - all are lovely, with stunning flowers ranging from shades of mango and melon, to a very ‘true blue’ in Tropaeolum azureum. 

All the species are growable, if you can provide an environment in which they can thrive - essentially, cool to cold temperatures, and fresh, moist air. Not the easiest conditions to recreate in the modern penthouse, but if you own an old. drafty New England home as I do me, you may have little problem at all.  Indeed these are plants best grown in a cold window, sunroom or greenhouse. ‘Cold’ being the operative word here, for most of these tuberous species demand temperatures below 70 degrees F, and they will go dormant again if they become any warmer. 

Curtis's features excellent diagrams and botanical drawings of the genus, with a long article on T. tricolor. The flowers are so tiny, that they are hardly 3/4 of an inch long.
In Chile, the plant blooms more profusely, and in case you were wondering, Ornithophily is simply a term that means that the flowers of this species is dependent on hummingbirds as their primary pollinator with only two species known to visit these blossoms. Not surprising, even our honey bee's could not fit into these blossoms although a giant bumblebee high in the Andes is threatening one species of hummingbird which is dependent on this species because it has a long tongue that can reach the nectar deep in the flower.

Of course, if Lydia lived in the Andes, no Bumblebee would have a chance of ever leaving a blossom.


  1. absolutely exquisite!
    thanks for sharing, I'm always on the lookout for unique and rare houseplants!

  2. Fascinating and beautiful! I don't think I'd have the patience for a 3-year dormancy. Although if I had a greenhouse I suppose I'd adjust my attitude.


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