After five years of work, 5,750 panels of toughened glass will help keep hundred of plants safe from Scottish winters – but more work needs to be doneIn the early autumn sunlight, Royal Botanic Garden Edinburgh’s extensive plant collection appears safe in their glass enclosures. But danger lurks from above for the tropical ferns, cycads and rare alpine heathers.Soon the September sunshine will give way to the storms and gales of the Scottish winter, which can bring hundreds of glass panels crash