My kitchen is where basil plants go to die. When I go to buy a basil plant, all the ones in the shop shrink back and hope I'll choose a different one, like when Sid in Toy Story chooses a toy, except in my case it's not deliberate. I try to keep them alive, but have accidentally killed more of them than I can remember.
But I currently have one which has been flourishing for several weeks. It might just be luck, but I think I've learned in the process, so I'd like to share what I've learned, in case others have the same problem.1) Only water it when it's wilting.
This is the most obvious piece of advice, in that it's usually on the packet. But it needs to be combined with 2) and interpreted with 3).2) Only water it in the morning.
This sounded like superstitious nonsense when I first heard it, like only watering it during a full moon; but then I remembered how plants photosynthesise in the day and respire at night, so it makes sense. If you water it in the evening it'll sit there in a puddle all night not photosynthesising, and I think having soggy roots is the main danger. But I and one ex-basil plant have demonstrated that 2) is not enough unless combined with 1) and 3).3) Wilting and dry leaves are not the same thing.
The current verdant incumbent, the Catherine Parr of basil plants, starts to wilt occasionally, gets watered, and revives. When it wilts, the leaves collapse and start to shrivel but remain a rich dark green, soft in texture, maybe even a bit squishy (think of wilted spinach). Whereas what has often happened in the past is the leaves keep their shape but go dry and papery and yellowish-white, and I in my botanical cluelessness go "Oh, the leaves are drying out, it must need watering." So I now think the papery leaves are a sign of soggy root death.