I have a 4th floor balcony with metal railings, so there's lots of opportunity for the wind to blow through. I have some small plastic pots which I am most concerned about. Any trick to protecting them from blowing over? Maybe group them together? Tie some type of hidden string around the pot and secure to a railing? And what about the two windowbox planters I have sitting on my outside sill? I don't have to worry about them injuring anybody as my outside sill is a part of the balcony; the most the windowboxes could do is fall onto the balcony floor itself. But what can I do so they don't fall off the sill (from high winds) in the first place? Or do you think that in normal winds, the dirt and rocks in the planter should be enough to weigh it down?

Tx!