Timing is Everything:

Refrigerate pesto for several weeks in a well-sealed container, completely covered with a layer of good olive oil. To use, uncover and tilt the container to let the oil run to one side. Scoop out the pesto and cover the remaining pesto with the olive oil.

To freeze pesto, combine all the ingredients, except the cheese and salt. Separate out the portion you’d like to freeze. For this portion, add salt sparingly and omit the cheese. (For remaining portion, add regular amounts of cheese and salt.) Freeze the pesto, covered with a generous layer of olive oil, for up to three months. Add the cheese and more salt after thawing.

Here’s the Scoop: On Storing Fresh Basil

If you don’t grow your own basil, try to purchase bunches with the roots attached and fully intact. Fill a tall glass with cool water and stand the bunch up in the water, completely submerging the roots. The basil can stay out, at room temperature, for days this way (it’s actually a beautiful and aromatic addition to your kitchen!). Change the water daily. (If your basil starts to quickly wilt, it probably wasn’t fresh, so clean and dry the leaves and use them as soon as possible.) To store basil of average freshness, wrap the roots with a very damp paper towel and store the bunch in the refrigerator in a loose-fitting perforated plastic bag.