I'm a beginner and decided to sow sweetcorn to grow in my newly acquired greenhouse (having just moved house). All 13 plants are growing very well and are now over a foot high, after potting on. However as I live in central Scotland I was intending to grow these in the greenhouse but I understand they need the wind to pollinate the group. Could I leave them in the greenhouse with the door open or do I need to move them outside to pollinate? Or would using a brush work instead?