Plants flowering early

Wondering what might be the cause of abnormally small plants, ie plants that go to flower/fruit with much less vegetative growth than expected ... I've sowed millet for example over several areas and the plants get to 1" tall then go to seed. I'm thinking it has to do with daylight cycle differences between where I am and where the seeds came from. Since I'm much closer to the equator than where the seeds are adapted to, they notice the short light cycle but high light intensity and heat, and this makes them think they're quickly approaching fall so they set seed while they can. Could anyone confirm if that makes sense or could there be other reasons? Thanks

What is going on sounds a lot like your plants are bolting. Essentially, when a plant is bolting, it means that the plant is thinking, "EEEEP! It is too hot/cold/whatever!" and the plant reacts by rapidly flowering and producing seed to ensure a future generation.

Millet is drought-hardy, tolerant of poor soils and hot weather, making it a staple crop in Africa and India. We've had some hot sunny days, enough to dry out the top few cm's of soil a bit, but always cool, dewy nights down in the 50s. Its also been raining periodically, a cm every 2 days or so marked by a nice 2-3cm rain once a week. Seems to me like perfect conditions for something like millet to thrive, some hot drying days followed by access to water to really spur growth. I was having the exact same thing happen during the rainy season with the millet, which I was attributing to too much moisture.

Strangely I've also noted the same thing happening with sunflowers I planted, some are about 2ft and still going vegetatively, others are starting to bloom a tiny flower at about one foot high. They're dwarfed somehow. The biggest difference I can see is where there's good topsoil at least the sunflowers are going strong; the millet still hasn't done much at all. Where the soil is poorer is where I'm noticing the dwarfism. I'm not really sure if its bolting in the normal sense. Doesn't that normally happen with cool-season brassicas that are too hot?

Bolting doesn't have to be heat related; it just means the plant is too stressed out from one thing or another and is going to seed. It could be something else that is stressing the plants out? On a sidenote, everything is blooming earlier around the world due to global warming, too.

It is most likely not the heat or lack of rain with millet. Is the soil compacted or poorly drained?

The soil is very well drained and has a nice structure to it, not compacted either. I'm thinking its a lack of soil biology, what I didn't mention was in this spot the topsoil had been removed to be used elsewhere; I left things as they were to see if I could get the biology going again from scratch basically. But still, there must be something to do with the 12/12 light cycle here because many plants grown from seed will begin to flower early here. It's still a bit of a mystery to be solved.

ahh, the topsoil was removed. I think you have your culprit.