It's based on other plantings of the same crop. If you plant a crop, and the only other record we have of that crop is 23 days from planting to harvest, that's what it will predict for you too. If it's wrong, it means the system doesn't have good data for that crop.

which plant has only a 23 day life span for you?

was it snow peas? ?I've added some better sample data which has pulled the median lifespan to 70 days - which is more realistic.

Thanks, yes it's snow peas. Sorry I'm still new here, I posted this from the snow peas page so I thought I was leaving a comment on the plant

So how would this have happened - someone pulled out their plants before harvest, so the lifespan was shorter than time to harvest?

Yes exactly that. If we only have data from users whose crops failed early, or who planted already advanced plants, then it can calculate it wrong. It just works off the median of all users.

Possibly we can do better if we can find more data.