Graft all forms of plants (not including flowers and alien plants) into one single plant.
eg. graft potatoes and carrots into one plant.

potato
`````\
`````potato+carrot
`````/``````\
carrot````````\
````````````merge
```Pear```````/
``````\``````/
``````Plantain
`````/
lemon

After doing this with all plants, keep going never grafting the same type of plant twice -so dont graft potatoes twice, not the individual plant but the "type" of plant.
after merging all the plants merge the merged plants together EG.

Apple
````\
````Pomegranate
````/````````\
Cherry`````````\
`````````````merge
Strawberry`````/`````\
```````\`````/``````\
``````Dragonfruit`````\
`````/```````````````\
Snapdragon````````````|
```````````````````merge
potato```````````````|
`````\``````````````/
`````potato+carrot```/
`````/```````\````/
carrot`````````\``/
`````````````merge
`Pear`````````/
`````\```````/
``````Plantain
``````/
`lemon

once that's completed continue till you've merged all plants into one mega plant.

*clears throat in simlish*

I did a lot of grafting back when in a family and I may be 100% wrong, but I was thinking there is a max we can do in one plant/tree? Maybe 4? So is this even possible, not that I would want to do it.

Just read that the max a plant can produce is 10 harvestables, so who knows what would be there to harvest if this is done? But seeing as I have not even opened the game since about May I won't be checking on this.

When you graft plants they split up their harvestables. So if you graft a carrot+potato then you'd get a 50/50 split. If 10 harvestables is the max then at most 10 could be grafted and still yield. They would produce 1 of each only. However, I'm betting they coded it for less so probably as someone else mentioned 2-4 being the max.