I used to believe that mirlitons could be grown in full sun. Not anymore. Intensive heat waves in the last few summers destroyed most vines that had been grown in full sun. The only ones that survived were in natural shade or had shade cloths. We learned the hard way that mirlitons need partial shade when there is prolonged heat above 95 degrees. That, along with substantial ground irrigation, can get us through another Heat Dome or intensive heat wave.
We also discovered that shade cloths may increase the amount of fruit that the vine produces! Not only does shade protect the vine from solar radiation and make it healthier, but it also makes it more bountiful.
Build your trellis so you can easily mount a shade cloth over the vine.
It can be thrown over the vine or mounted over it. Shade cloths come in different shading percentages, and we recommend 40% cloth with grommets so it does not blow away. They are available at Amazon and most big box stores. Shop around online to find one that will last for years. An Amazon link is here.
Shade cloths are only for extreme weather events. You won’t need it unless there is a heatwave where the temperatures stay above 93° for several consecutive days. Too much shade, especially in the spring and early summer, can be detrimental to the vine. The leaves need sunlight for photosynthesis to provide energy for the plant. Sunlight is a natural fungicide that prevents some plant diseases. Full sun also dries and hardens the leaves, making it more difficult for fungus to get a foothold on the vine.