Four - from seed. I would divide, or, if you only want/need a single plant, cull the 3 weakest. BTW - if you do divide, remove the lower leaves & plant the plant much deeper for a stronger root system.

Al

Thanks Al, I was suspecting this was the case.
The picture was actually taken *after* I divided the seedling that I bought into 5 smaller groups, thinking each one was a separate plant. So there must have been at least 20 plants in there. I wish they had told me about division at the store...

Anyway, I culled as you suggested, hoping to get some nice growth. Thanks again!

Alternatively you can just leave them alone and grow them as one clump. They all look a pretty healthy and a bit past the thinning out stage.

Oops - just realised it's too late. You've already taken action. Have you thrown away the ones you culled? If not you could pot them up individually.

flora_uk: I repotted most of them, unfortunately I don't have that many spare pots. But I found good use for the rest - ate the leaves, put the rest in the compost bin.

Look to your recycle bin for all manner pots. Plastic containers from food items can be washed and have holes punched in the bottom for drainage. Certainly not the pretty Martha Stewart-styled pots, but they work. So does saving pots from purchased nursery plants.

FataMorgana

2 weeks later, the basil is as happy as I've ever seen it:

Thanks everyone for your help!