Sunday, November 12, 2017
Hylocereus costaricensis, sun, shade and cold
I recently tried growing six Hylocereus costaricensis cuttings attached to the external walls of a house as 'epiphytes' over winter in zone 9 (Wellington, New Zealand) . B & T World Seeds say they take zone 9, though most authorities say zone 10 or above.
I put two of the Hylocereus costaricensis cuttings on a mostly sunny wall, two on a wall with half sun and two on a mostly shady wall. To my surprise the cuttings in the shady spot died, one of the cuttings in half-shade died, the other looks sick while the cuttings in full sun (one pictured with new spring growth) were fine, if a little sun burnt.
This result was the opposite of what I expected, usually it is recommended to protect tender plants from sun if cold is expected as it is the sudden change in temperature when the sun hits them in the morning that usually kills them. Apparently not the case with this cactus and probably others like it.
The cuttings on the sunny wall were also higher up than the others, it's possible more wind exposure and air circulation helped them to survive.
I don't yet know how well this plant grows here aside from surviving winter. According to Russell Fransham Subtropicals, where I got the plant, it needs sustained warmth over 15C to produce the delicious fruit. I may try getting it to grow on a black surface to raise the temperature if things don't seem to be going well.