We're at the peak of fresh basil season and my biggest challenge is always how to keep it green and fresh for as long as possible. There are just two of us so we don't consume this leafy herb as quickly as say, a family of five, and yet we love it. I have tried so many ways to keep those leaves green. I've wrapped the basil in paper towels and kept it in the crisper. I've soaked a wet paper towel, wrapped it around the roots, and then wrapped that in tin foil, and then kept it in the fridge. I've put the basil in a glass, covered the roots with water, and then kept it on the counter. In every one of these instances, the basil browned, wilted and became unusable within a few days.
Now here's the killer-tip for keeping basil green, compliments of the July 2011 issue of bon appétit. When the basil reaches your kitchen from the garden or farm stand, trim the stems as you would cut flowers to remove the roots and/or dried ends. Then, stick the bunch in a tall glass, jar or vase filled with water covering the ends. (Try to ensure no leaves are in the water; trim the low leaves off and use immediately.) Now, here's the magic, cover the basil leaves with a large plastic bag and keep it on the counter. Doing this will allow the basil to stay vibrant and fresh for at least a week. The basil in this photograph (taken July 11) was purchased from the farmers market on July 6th and it's still in perfect form as I write this seven days later.
So what's happening and why does this work? Well first of all "it turns out that basil is sensitive to cold" so it doesn't like the fridge at all. In addition, it "produces ethylene gas, which is what ripens fruit but deteriorates leafy greens when they're not allowed to breathe". "This method allows moisture to stay in while ethylene escapes", making for fresh basil for days after being cut.
Thank you bon appétit!