Why aren't my pumpkins growing?

[MeliodasWrath]

I planted lots of pumpkins, and not a lot of them are growing, simply saying 'Cannot grow.' Why? I have attached a screenshot so you can have a look.

 

[Conea64]

They have to grow on an open block next to the stem, leave a gap next to each stem

 

[remio]

From the Minecraft Wiki:

Perhaps this could help you solve the issue?

 

[MeliodasWrath]

Ah, thank you!