Translation:The plant has not germinated
But wouldn't adding "yet" place too much emphasis on the "yet"?
"The plant has not sprouted" still allows the possibility that it will sprout next week (though adding"yet" certainly sounds more optimistic).
Presumably "-ja-" isn't always optimistic? How do you express the idea that the plant has failed to sprout (and never will)?
"Mmea haukuota (na hautaota)." The "-ku-" negative past is an opportunity past/something that did not happen (it does not include the yet and is usually used when the possibility does not reamin). Weird negative example: Our househelp's daughter had been involved in a van kidnapping and my mother asked her if she was harmed to which the answer was "She has not been harmed yet." which sounds extreme to our ears, but she used the "ja"-tense as the perpetrators were still out there, leaving the possibility...
Farmers often talk in English about other things "germinating" when they are actually sprouting so the fact that ota means both sprout and germinate makes a lot if sense.
For example a potato or a woody cutting of cassava will sprout. When translating to English the farmers normally say germinated.