However, you could use some general terms, depending on the context:
* A grove of lemons - This is suitable if you're talking about a large group of lemon trees.
* A basket of lemons - This works if you're referring to a collection of lemons gathered together.
* A pile of lemons - Similar to the basket, this is good for a large, unorganized group.
* A squeeze of lemons - You could use this if you're talking about a small amount of lemon juice.
Ultimately, the best collective noun depends on the situation and the desired effect.