How Can I Keep The Squirrels From Planter Boxes On The Terrace?

I had the same problom and my gardner told me to use something called blood meal its a powdery mix looks like soil and the smell keeps them away. It is also
good for the plants. He told me they come to the plant take a sniff
and won't come back. I smelt it when I put it in but once it was watered I never smelt it again. I think the company I got was called scotts blood meal. Good luck