Plants not producing 10 harvestables

The plants grown on my sims lot (this isn't happening with wild plants) aren't producing ten haverestables. 
I haven't played with gardening for a while and I'm gardening with seasons for the first time so maybe it's a seasons thing, but when I had gardened in the past I'd always get ten plants so I don't know what's going on.
My apologies if this was intentional and I didn't realise.