This is a resubmission of the old version of this project that was still marked as a Map in PlanetMinecraft.

What are spreadable crops?
Crops can now spread naturally. This does not include all crops, but instead only the ones that can be planted on farmland or soul sand. The list of crops is as follows: wheat, carrots, potatoes, pumpkins, melons, beetroots, and nether warts. When a crop spreads, a smoke particle emits at the new plant and the old one. You can tell if you have a crop that can spread if you see the green particles, as shown in the pictures above. The new crop can spawn on any nearby empty farmland, dirt, or grass blocks. Spreadable crops will only reproduce when they are fully grown. Yes, this means you might have to watch a field of crops until they are fully grown, and then wait longer before they can actually start to spread.

Why can't I find any spreadable crops in my field?
Spreadable crops only are created by placing seeds of any of the listed types from above. Even then, you have to be sure the datapack is correctly loaded in your world. You will get a yellow confirmation message when you reload the world if it was properly installed.

Why don't crops always spread when they emit smoke?
Spreadable crops have the potential to spread, but they actually have a few random possible states. They are as follows:
* The new crop will be spread a few blocks away from the old one and the original crop will become no longer spreadable.
* The new crop will be spread like before, but this time the old crop will retain the ability to spread.
* The old crop will be dormant and is waiting longer to spread.
* The old crop will not spread and become no longer spreadable.

It is noteworthy that when a crop becomes no longer spreadable, it is still available to be harvested.

Are there any differences with nether wart spreading?
Yes. Nether warts cannot grow onto farmland, dirt, or grass blocks like the other ones. Instead, they require soul sand to be already placed nearby in order to spread. Like the others however, if no blocks are found that they can spread onto, the crop will not spread.

Are there any tips I should know about spreadable crops?
There are a few tips I have.
First, if you want to contain crops and prevent spreading beyond a distance, it is important to place blocks around the field that are at least 6 or more blocks thick. This will not guarantee that the crops won't spread out still, but it will contain the majority of them.
Next, I would suggest not making too large of fields. There could still be a lot of crops spreading in rapid succession. That does not sound like something computers would handle well. Plant sparingly, but not too sparingly.
Finally, and this is the reverse of the first one, but if you want a crop to spread, be sure to have a valid block nearby for the crop to grow on. This is easy for overworld crops, but nether warts do require soul sand and nothing else.

If you have any further questions, feel free to ask them in the comments below!