Many temperate plants will grow and flower in the highland tropics at 1000m elevation and above. In the Cameron Highlands in Malaysia for example, fuchsias, daylilies, apples, roses, pelargoniums and snapdragons grow and flower throughout the year. In the lowlands e.g. in Kuala Lumpur, at 100m, they survive for only a few weaks or may grow but not flower.
I have been trying to grow temperate plants by arranging for them to get a cold water shower for 15 minutes a night at midnight. The water is chilled to about 18 degrees Celcius. However the effect has not been significant.
My next option was to get engineers to design a flat bed cooler on which I can place containers of plants for their roots to be cooled at night. I have opted for cooling at night so as not to have to fight against the daytime high temperature of 30 degrees. At night there is a natural drop to 24 degrees, which is a help. However the engineers have not been able to design a flatbed cooler for me. I thought this would be somewhat like a mini ice-skating rink, but exposed to sun and rain and only switched on at night. Does anyone out there know whether this can be done?