I am growing basil in a pot outdoors and it's getting pretty big. How do I know when it should be transplanted to a larger pot?
There are really no hard and fast rules for repotting. For most plants, if you can remove the pot from around the roots, and the roots are all matted inside and retaining the shape of the pot, that is called root bound, and repotting is probably a good idea, for most plants. Other clues can be there's so much plant that the whole thing keeps falling over, or it doesn't seem to stay hydrated no matter how much water you pour in. Other than these things, most gardeners recommend that plants be repotted annually, to renovate the roots and replenish the soil. Here's an article that talks more about repotting: https://www.gardeningknowhow.com/houseplants/hpgen/learn-more-about-repotting-houseplants.htm