Posted: 23/08/2012 at 18:42
Do you mean in a plastic bottle used as a cloche to protect from slugs etc? If so, you don't need to, mint is a thug of the first order, we have several types here and all grow in pots so as to keep them out of the borders, or we'd have to move in a year or two, and not tell anyone they were there !! If you mean using the plastic bottles as a pot, no reason why not as long as you have plenty of drainage holes in it, and tuck it somewhere a bit shady - and where it will not freeze quite solid in the winter- tho' I suspect that might not worry mintt at all. Never grown it from seed, anyone who has some is usually very happy to give away roots, look around your neighbours, or ask around - gardeners are very friendly people who often are very willing to share what they have.
I would not sow seeds now, unless you have somewhere light and warm to keep them, keep the seeds till next spring ... hope some of this helps?