A protective cover for plants made from translucent or transparent rigid orsemi rigid plasticmaterial. This cover is comprised of double walls capable of being filled withand retaining water oranother liquid suitable for heat storage. The cover involves modularcomponents including side and/orend walls that are vertically separated and may be placed in series. Contactsurfaces between walls mayincorporate some curvature. The walls are supported by an external arch orother appropriatestructure. The walls may have a curved bottom that collects rain or otherwater and may act as a pivotfor opening and closing the vent area.The invention overcomes scale limitations of passive heat storing plant coversthat feature liquidfilled walls. The invention optimizes heat retention in liquid filledprotective covers and provides flexibleheight to width ratios. The invention also allows for adequate passive ventingin such covered areas viaconvection. These benefits are achieved via modular cover sections, includingdistinctive side or endwalls that are separated on vertical planes and include one or more curvedcontact surfaces.
