Ah, I think I see where our disagreement lies daffodil. You say "Cooking, gardening, and worms alone won't necessarily guarantee any science learning.". Now I think actually I would disagree with that to some extent-because I honestly don't see how you could cook or garden without some basic science knowledge and to be honest, that knowledge would certainly be more than was taught in schools to around age 8 in my country. So a child who was actively involved in cooking or gardening, I would say, would be of necessity covering some of the the basics of science.
But I think our main point of disagreement is more fundamental. See I don't see how any kid could be working directly with an adult, gardening or cooking, and not ask these very fundamental questions. And these are not questions that you need science training to answer. I mean, if you are stumped by them there's an entire internet out there waiting to answer such questions, often with videos and so on. So I'm coming from a sense that it is almost inevitable that these questions will be asked, regardless of how sciency or otherwise the parents, and once they are asked, you just don't then need a comprehensive science background to answer them. I'm not saying that you will never need this to homeschool. My son finds physics and astronomy really fascinating and I have been grateful for the physics/chemistry/maths I and my partner have studied: with us able to give him a lot of help plus Khan academy, ScienceJim, MITOpen, he's managing to work through a basic physics primer which gives him the systematic overview he's after. But he's nine and very in control of his own work. I should also mention that he's done nothing science wise really aside from cooking, gardening, some electronics and occasionally the odd chemistry experiment.
I also think that this is another point of disagreement. "Why start early? Well, the earlier you start hearing some of the important facts, the sooner you can really understand and use them. You need to hear or read or think about a science concept multiple times before you really get it and it gets permanently lodged in your brain as an easily-accessible bit of information. The sooner you understand the basics, the sooner you can start seeing connections between different ideas and asking the deeper, more complicated questions that you once didn't even know enough to wonder about. "
I'd actually interpret what is going on very differently. I'd say that if children aren't grasping these facts it is because they are really too young for them. Kids will often ask things they can't understand the answer to and sometimes therefore they need to ask the same question repeatedly as they get older, to get a more and more detailed answer. I've studied a lot of science as an adult and I would not say that I necessarily needed repeated exposure to science facts to understand them. I also think that kids are, inevitably thinking about a lot of these concepts. This may be a difference in how we view cognitive stages. I do tend to broadly follow Piaget etcs ideas about different stages of cognitive abstraction ability and so I think that the ability of a fourteen year old to understand something like photosynthesis cold is just exponentially greater than that of a four year old, its got nothing to do (IMO) with that ten extra years of talking about plants but rather about brain maturity and processing ability. So that's a difference of opinion.
Interesting discussion! And living in Wales where our patron flower (!) is a daffodil, I love your username!
ETA just wanted to add something else. I'm not coming at this from an unschooling perspective, though I have huge respect for that viewpoint. I do see the value in systematic, progressive study in certain areas (in our house this is maths and music). I just don't see its value in science for younger kids.