Thyme, Oregano, Sage and Chives are all perennials. They will usually flower every year and there is nothing amiss with that. It does not mean the plant is doomed. You can use the flowers.

Parsley is not perennial, it is biennial. It shouldn't flower in its first year but will always flower in its second year. If it flowers earlier it is probably stressed by lack of nutrients or lack of water.

Lettuce should be harvested before it bolts. Heat and stress cause it to bolt earlier than it should.

Dill bolts easily and you need to sow it little and often in succession.

Basil planted too early bolts (goes to seed) long before the tomatoes are ripe, which is when I want it. I sow my basil around June first--they are just getting their first true leaves. Your lettuce was probably sown very early, and it's bolting because it's time. If you had sown a later crop to replace it and your weather is still cool, you'd have lettuce still.

We also planted lettuce very early because I got seedlings from a school greenhouse where they had extra, so I had to put them somewhere! They did great, and we harvested them for a good month straight, but they did get bitter due to the heat and age and were ready to bolt. Then the deer ate them, so I pulled up the rest. It does get very hot here, so no more lettuce in our yard until fall.

Thanks for responses. Actually I live in Idaho and the days are VERY long right now (light by five a.m. and darkness arrives at ten p.m. or later). My thyme, oregano, and parsley are all suddenly gone to seed. They are planted in rich nutritious soil and watered regularly, so I know that's not the problem. My parsley has tree branches for stems, thick and awful. The lettuce is fine so far, no problem. I would love to grow cilantro but don't dare because it bolts before I ever get any leaves. So frustrating!! We had a couple 95+ days and then it cooled off, but our really hot weather is coming.

Your days are the same length as mine at the moment. However, the hottest place in the country today was 72 f.

You cannot stop parsley going to seed if it is in its second year. It is not a perennial, it is a biennial and has a finite life. If you cut off the flower stems you might get it to hang on a little longer but you can't stop it seeding and dying.

As we said above Thyme and Oregano are perennials and there is absolutely nothing wrong with them flowering. It is totally normal for them. It doesn't mean they are going to die or that they are unusable in the kitchen.

BTW the Mediterranean herbs ie Thyme, Oregano, Lavender, Sage and Rosemary do not want rich nutritious soil and lots of water. That is more likely to kill them off than lean living, a little water and excellent drainage.

It is helpful if one treats herbs as individual species rather than as a group called 'herbs'. That name is only useful in defining their use, not their needs or characteristics.