Most people consider Tropaeolum speciosum to be the hardiest species. I have never been able to establish it, I think because of slugs, but it does well in many gardens as cold as mine (typical winter minimum about 15 F/minus 10 C, sometimes lower). In nature it is a woodland understory plant climbing through brush and hanging outward, often on steep slopes. T. tricolor grows at low (near sea level) to mid elevations, also climbing through shrubs, and probably does not experience very low temperatures in the wild, but it's widespread and perhaps some populations from the Andes foothills south of Santiago would be hardier. There are quite a few subalpine species, of which the most likely to be in cultivation are T. polyphyllum and T. incisum, of which the latter may be tougher but also harder to grow. The species that reaches the highest elevation (4,000 meters) is T. nubigenum, which I have not seen in cultivation. These and T. sessilifolium grow well into the snow zone in the Chilean and Argentinian Andes. T. leptophyllum and T. looseri are reported from somewhat lower elevations, in the foothills. Generally they do not climb anything, but instead sprawl flat. My impression of the climate where these higher-elevation plants grow is that it is much like that of California's Sierra Nevada. That is, anywhere temperatures become very cold, there is snow cover all winter, so the ground does not freeze deeply. The tropaeolums emerge just after the snow melts and flower in early to mid summer, depending on elevation. T. tricolor is spring-flowering. I have dug down to see how they grow, and the tubers and rhizomes are very deep in rocky soil, often in soil "mulched" by broken rock, which keeps the moisture in. They can also be seen flourishing in gravel railroad embankments. My only experience with growing a Tropaeolum in freezing temperatures is with T. brachyceras, a small-scale yellow-flowered climber, which has survived about 25 F here in the bulb frames. Jane McGary Northwestern Oregon