It Needs Moisture
In order for mildew or mold to grow, it requires a humid environment. Humidity in excess of 70% and warm temperatures above 65 degrees create an ideal environment for mildew growth. This type of environment can be found many places where clothing may be stored. A clothes hamper in a bathroom without adequate ventilation may see much mildew growth on clothing. Clothes that are stored in a damp closet, basement or crawl space are also at risk. If the air cannot circulate where the clothing is stored, chances are mildew is a possibility. Poor ventilation can add two gallons of water to your living space with cooking, laundry and showering, so finding an exhaust fan for humid places in your home is a good idea.
It Needs Darkness
Sunlight and heat actually kill mildew, so what better place to find it thriving than in a dark box, drawer, hamper or closet? Before storing your clothes make sure they are completely dry and have adequate ventilation so there isn't any way for mildew growth to begin.
It Needs a Food Source
Mildew is a living organism, so it requires what any other living organism requires: food. The nutrients that mildew needs to live can be found in paper, wood, dirt and fabric. It will feed off these materials, so if you find mildew on your clothing, you're in trouble. The mildew will weaken and eventually rot the fabric of your clothing. If you don't want to see your best T-shirt ruined, it's best to keep your clothes out of a dark, damp environment that will promote mildew growth and the feeding process.