(Updated 8/7/18 with alternative method to preserve fresh basil)
Believe it or not, the bunch of Thai basil in the photo below is three or four weeks old (it’s been so long that I don’t remember). And yet it is almost as bright green and lush as it was on the day I bought it.
I don’t remember where I heard this tip, but since it works so well and it is basil season, it’s worth sharing.When you bring your basil home, trim the stems with a clipper, remove the rubber band or twist tie, and place the bunch in a glass or vase. Add a few inches of water to cover the base of the stems. Then take a plastic bag and cut a few holes in it (the fresh shiitake mushrooms I buy come in a bag with holes pre-made, so I often re-use them for this purpose). Place a plastic bag over the basil leaves and place the assembly in a well-lit location, but out of the direct sunlight. Check the water level daily and add more as needed. If all goes well roots will start sprouting from the basil, converting it into a pseudo-hydroponic system. The photo below shows how it looks at the end.
The plastic bag provides a moist environment for the basil leaves; the holes in the bag prevent too much moisture from building up (which can cause rotting); the water, although nutrient free, keeps the basil alive; and storage at room temperature allows the plant to function normally.
Another example of the success of this method: a bunch of basil that I finished last weekend had been on my counter for at least six weeks.
Update: alternative method
The plastic bag method described above is a little messy and unruly, so I have been thinking about alternative methods. One Saturday in July, one came to me: use a large container and set the entire thing onto a cooling rack to allow air circulation.
An example is shown below. After trimming the basil stems, I put them in a mug with some water. I set that on a cooling rack, and then put a large plastic container over it all. It worked — the basil stayed fresh for several weeks.
(Bonus ‘nerd points’ for those who can identify the source of the mug in the photo.)
(Originally published August 5, 2007)