Old seed viability?

[JohnAndSancho]

I'm pretty sure I know the answer here, but y'all are smarter than I am. 

 

My brother rearranged his room and found a bunch of seed envelopes clipped together so I'm assuming they're the same age. I've got 2 varieties of sunflower, one is labelled the other is a mystery - some tomato seeds, and some watermelon seeds. 

 

They're dated 2018. 

 

Is this one of the times where I just throw them in the compost heap and see what happens? I really don't want to waste my limited stock of soil or planters on them. 

[PalmsandLiszt]

No idea specifically, but watermelons in nature are basically desert plants, and desert plants will often have seeds capable of quite long periods of dormancy, although 7 years might be pushing it.
On the other hand, you could just buy a watermelon, eat it and get fresh seeds anyway...

 

[meridannight]

It depends on species and it depends on the conditions they've been kept in. If the seeds aren't moldy and you have the space to try them, I would plant them for sure. You probably won't get much, but there may be some surprises there.