Planting/Harvest Question

Hey all

Wonder if you could clarify something for me ~( ill try my best to explain)

Do plants come ready to pick depending on how long they have been growing or on the seasons.

The reason I ask is on the back on all seed packets youll see a sowing and harvesting period of a few months.

I thought this means if you plant say a few brocolli every few weeks you would get a new supply every few weeks in a few months  times.

But i have found that even though i planted mine a month apart, all three batchs are ready to pick right now.

The same could be said for my sprouts etc that are all different sizes from the different batchs i planted but all the veg on them seems the same across the board, will this mean they will all come to harvest at the same point as theyre driven by the seasons rather than how long they have been in the ground for

sorry if that doesnt make sense but in my head i would have thought plants would harvest all at the same time as they respond to seasons regardless of when they were planted


thanks all

ah thats what i thought as now have a glut of purple brocolli though im not moaning