In my garden, for newly renovated beds, I place dozens or hundreds of little leafless bamboo shoots --since I have over a hundred square feet of bamboo. These little daggers let sun and rain through, and plant seedlings can come up, but cats avoid getting stabbed. When weeding the neds, I get stabbed.
Once I bought a patented plant that is said to repel cats, digs and
rabbits. It has been sold as Scaredy Cat and Piss-Off plant; it is
Plectranthus 'Sumcol 01' and you would need to buy
enough to cover whatever area you wish to keep cats from. It is a cold-tender
perennial, related to Cuban Oregano, a Coleus-like plant in the mint family.
Arthur Lee Jacobson