Hi Mint is an aggressive grower by creeping through the soil,enclose your mint with slates down about 10ins into ground or similar restrictions,your mint is usually trouble free,die back in winter and reappears in march,during spring clean the surface of the bed and top dress with farmyard manure or compost,make a fresh bed every-third year as plants will exhaust the soil, to have winter mint lift some two/three year old roots in oct place in pots or boxes of good soil for gentle forcing in greenhouse or where you van at temperature of 13oc/55of. This will provide you with the fresh mint you require,All the best John