Cold-damaged mirliton leaf.
Freezes and frosts are not the only cold temperatures that can damage mirliton leaves. While not as damaging as frosts, Cold Damage can occur when temperatures drop below 50℉.
Cold damage symptoms often appear several days later and include limp, wilted, or yellowing leaves, and subsequent slowed growth. Light cold damage can generally be outgrown by an established vine, but young, newly transplanted plants are more vulnerable. So protect them by covering them with tarps or buckets and even adding a heating element.