There are few ways of preventing squirrel from destroying your plants in your garden. Of course, the most gruesome way would be to poison them but it is not recommended and in some areas it is illegal to do that. The best way is to discourage them from having access to digging your garden soil.
I have tried a lot of methods mentioned in the internet such as trapping squirrel and transporting them to far off places, spraying cayenne pepper, moth balls, bleach in rag clothes, growing daffodils, putting burnt ashes on the soil, animal and human urine, black mulch. I must say some method temporarily worked, and is not meant for long term solution, while some methods were total failure.
I won't go into deep details of the methods that failed but I can mention one most effective way to humanely prevent squirrel from digging up your plants in your garden. I have used this cheap and simple way for few years now, and I was able to grow some very healthy vegetables and plants without the squirrel destroying my garden plants. I have included some pictures which is self explanatory and you would understand immediately what I meant just by looking at the pictures.
Here are the steps I took in preventing squirrels from digging up my plants:
1. When your plants are young seedlings, you use a clear plastic plant cover which can be bought at most dollar store or garden store. What I added was a white soft thin foam sheet stuck with cello tape on the side of the plastic plant cover. This white foam will protect the young seedlings from the intense heat of the sun during the hot summer.
There is a hole opening on top of the plastic plant cover which allows you to water the plants.
2. When your seedlings had grown big enough and the tip of your plants are touching the top of the inner clear plastic plant cover, you will then remove the clear plastic plant cover.
3. Use two or more bricks and put them surrounding the stem of your plants like in the pictures above. Then you put pebbles around the remaining gap to completely prevent the squirrels from accessing the soil.
4. If you want you can also use a combination of plastic mesh, skewer sticks and pebbles, just like in the pictures above.
5. Squirrels usually dig into your garden soil to hide their goodies such as peanuts, cherry, fruits and other nuts. They also enjoy eating some of the plants roots. Now when you put several heavy bricks around your plants stem, the squirrel has no chance to lift the bricks to dig up the soil around your plants. So they move on to find other easier to dig soils.
The pebbles further discourages the squirrel from digging because squirrel hate having to move the pebbles while digging. Squirrel likes soft and easier to dig soil type, especially potting soil mix. Squirrel very rarely touch or eat the stem of the grown up plants, which is why you need to fully cover your plant initially, with clear plastic plant cover, when the plants are very young, in their seedling stage.
So there you go. This is by far the cheapest and the most effective way to prevent squirrel from destroying your garden plants and flowers. Besides, putting bricks and pebbles around the stem of your plants and vegetables makes your garden look very stylish and beautiful, as if it adds to the landscaping beauty of your garden.