There are several ways to keep possums away, according to the search results:

1. Eliminate food sources: Possums will be attracted to your yard if they can easily find a source of food in it. If you take away the source of food, opossums wont have much incentive to stick around. This source can be pet food that is stored outside, unsealed trash cans, or even fruit that has fallen to the ground from your fruit trees.

2. Use strong odors: Possums are attracted to many smells you find distasteful, but there are some nasty smells that even they hate. These include ammonia, mothballs, vinegar, garlic, onion, peppermint, and camphor. You can pour some ammonia or place some mothballs in a coffee can and leave it in your yard. You can also plant onions and garlic around the edges of your garden to help deter possums from getting in. Another option is to spray a solution of bleach and water around areas you want to keep possums away from. You can also mix one part molasses with four parts of water in a spray bottle and spray onto leaves and branches that possums climb to get in.

3. Make your yard less hospitable: You can make your property a bit less hospitable by trimming the trees to cut the access to the roof and stop possums from getting into your home. You can also put up fences around your garden and other risky areas in your property where possums can find their favorite food. Patching up holes that the possums may use as entry points to your house, cutting the grass, not leaving rubbish or food lying around for the vermin to feast at, and moving the rubbish are other ways to make your yard less hospitable.

Its important to note that its illegal to kill or harm possums, so its best to use humane methods to keep them away.