Gardening

That’s called bolting. Here is a website that can help you since it could be any of a few different things causing them to bolt.

https://www.epicgardening.com/bolting-basil/

It is normal and yeah once they start it can be hard to stop. You can try cutting them back more aggressively to see if that helps, but ultimately basil is a short lived plant and eventually it will flower and die.

Thai basil is completely fine to let flower, but you want to pinch the tops early on lemon basil (and traditional genovese) so they keep producing leaves and don’t go bitter.

That lemon basil is a writeoff; you have to be proactive about the pinching or the plant will go all-in on dumping seeds.

Try to keep the soil cooler, water with cold water. It looks like it’s in a very shallow planter right now so keeping the soil cool will be difficult. I’d put the plant in a deeper pot with more soil volume and wrap the pot in foil to reflect sunlight if the pot is in a place it gets sun all day. It might not solve the issue now that it’s already started but keeping the soil cool and moist will help slow it down or prevent it all together if you’re doing it from the start.

I generally don't as they are perennial not annual. Yeas I suppose you can too them but you aren't getting much for this. I guess top if you please but I've found letting them go with flowers gets me overall.move leaves and its one less chore.

Nuclear winter