When we plant stuff in the garden, the plants don't exactly care about what we want out of them. The plants have one goal: to create seeds and reproduce. Sometimes, this goes in our favour, for example, if the seeds are inside of a fruit that we want to eat (tomatoes, peppers), or it's the seeds themselves we want to eat (beans, peas). But in some cases, plants producing seeds early is against our interest.
Plants like cabbage, lettuce, broccoli, carrots, spinach, parsley, basil, herbs in general, if they go to seed production, they're no longer edible for us, at least in the most convenient sense. When cabbage and lettuce go to seed, or as we call it 'bolt', they will start growing up, creating flowers, and will change their flavour and consistency into very bitter, no longer edible taste for us. Carrots will become fiberous and too tough to eat, broccoli will become flowers, herbs will quickly reach their end cycle of life, and will stop producing all the tasty leaves we want to harvest. So, what do we do to deal with this?
First thing we do is watch out when we plant. A lot of plants will go to seed immediately when it's hot enough, so we plant broccoli, cabbage, kale, lettuce and all these frost-hardy plants when we expect it to be cold for a while. Carrots and celery will also grow when it's cold, however if they survive the winter, they will bolt as soon as it gets warm again. This just means, plant them early enough to reach full size before late spring.
Herbs are generally planted in the warm weather, but that's okay, because we have different ways to stop them going to seed. First thing you can do is to plant them in a very rich soil and fertilize them with nitrogen. When plants get extra nitrogen, they immediately decide to use it for more green growth, and you want them to grow as much greenery as possible. Second thing you can do is to prune them.
Herbs will keep trying to go to seed no matter what, so if you take off their top parts that are trying to flower, or about to try to flower, they will get rebellious and grow 2 tops just to spite you. If you take these off too, they will grow 4. This way you can keep taking their tops until they grow into big, bushy plants, with tons of lush growth on them. This will not only make them bigger but also prolong their life. They'll keep growing more until the weather is no longer good for them to grow, or you stop fertilizing them.
I've seen plants go to seed when they're not liking their living situation; they're in a pot that's too small, or the soil is bad, or there's just not enough nutrients for them to grow big before producing seeds. These plants need to be stopped from growing flowers and transplanted in a better place in order to grow big. You want your plants to feel like they have the luxury to grow big and strong before they start producing seeds – because that way, you get more produce!
Another type of plant you can get to grow bigger and stronger are flowers! For the flowers, they're going to seed when their flowerheads start to dry and the seed is produced inside. To prevent this, you can take all dead or dry flowers off of the plant. She will grow double! This practice is called 'dead-heading' and it commonly used to make flowers look very lush, neat and healthy. It's also okay to take flowers off before they've even reached the dry stage, and the plant will spitefully double the amount of flowers on her. I've gotten to harvest just outrageous amounts of chamomile flowers this way. It's good to do it with roses, and my cosmos flower is also dealing well with it. There are some flowers this wouldn't work with, like tulips and bulb-based flowers.
