Younger offspring: Hey, look what I grew!
Dr. Free-Ride: Wow, those are tall.
Younger offspring: It's a bean plant.
Dr. Free-Ride: I recognized the shape of the leaves. From the looks of it, you actually have more than one bean plant growing in there.
Younger offspring: When it gets warmer, we should transplant it into one of the garden beds.
Dr. Free-Ride: Mmm. We could try that, but all my garden books warn that beans don't transplant well.
Younger offspring: Then we can just grow it in the cup.
Dr. Free-Ride: OK.
Younger offspring: And then I'll harvest the beans. But I won't eat them, because I don't really like to eat beans.
Dr. Free-Ride: Kiddo, I'd be really surprised if we were able to harvest any beans from a bean plant growing in a cup. It has so little room that the growing is all sped up, but I don't think it's necessarily healthy enough that it can set beans to harvest.
Younger offspring: But look, it's already grown some beans!
Dr. Free-Ride: Umm.
Younger offspring: See them?
Dr. Free-Ride: So, what did you plant to grow this?
Younger offspring: Beans.
Dr. Free-Ride: Yeah. What you see right there, on the stems that came up out of the soil? That's what's left of the seeds you planted. The embryos of the new bean plants were inside the seed. When the seed germinated, it split and the embryo grew roots and a stem and leaves.
Younger offspring: Oh.
Dr. Free-Ride: To get new beans, the plant has to make flowers, and those get pollenated. Then you grow the pod that has more bean seeds in it.
Younger offspring: I didn't know that.
Dr. Free-Ride: I guess when we've talked to you about "the miracle of life," we've focused on the animal kingdom, rather than the plant kingdom.
Younger offspring: Yes, I know all about where animal babies come from.
Dr. Free-Ride: We needed to have a talk that was actually about birds and bees and flowers!
I look forward to reading your post on having explained double fertilization to them.
If it will cheer up the child, beans tend to survive quite well from being planted out from modules (although they're not fond of the root disturbance of being pricked out from trays). Round here (England, with cold, clay soil), a lot of people start beans off in modules indoors because of our short growing season - the soil's often not warm enough to sow beans direct until into June. It's probably less perfect than direct sowing, but they don't rot in the soil, they don't get eaten by mice, they don't get caught by a late frost, and they're a month or more ahead of the outdoor-sown crops. Put the whole pot-ful into a rich soil underneath half-a-dozen canes. If you're in a frosty area, nip the tips out and pot them on into a 7" plant pot until after the frost risks.
How complicated a view of plant reproduction will you go for? Is he/she at the age to appreciate the weirdness of ferns and clubmosses as well as seed plants?
I think you need to do this unit at home from Topscience:
Then they will totally know about beans (and corn!), including what happens to the plant if you snip those little beans off when the first leaves appear!
Really, you'd have fun!
I'm determined to grow a successful crop of lima beans in Massachusetts. I'd already decided to try starting them indoors this year, but a la stripey_cat's suggestion, I'll start them in peat pots. I'll let you know if it works!