cold frame 
noun
A frame with a glass top in which small plants are grown and protected without artificial heat.Sow seeds of herbaceous perennials and alpine plants in a cold frame or unheated greenhouse....
- Bulbs forced inside or grown in cold frames in portable containers can easily be placed into large, outdoor containers at flowering time.
- According to our thermometers, this combination was not as protective as cold frames covered with glass, but the plants didn't seem to notice.
- nail head
- nail-headed
- nail-head molding
- nail-head moulding
- nail-head spar
- nail-hole
- nailing strip
- nail-keg
- nailless
- nail-like
- nail-maker
- nail-making
- nail one's colours to the mast
- nail (or pin) one's colours to the mast
- nail parer
- nail-paring
- nail-passer
- nail-plate
- nail polish
- nail polisher
- nail polish remover
- nail punch
- nailrod
- nail scissors
- Nailsea