I have one extra potting soil bag and a part of my garden needs some soil. Is it okay if I put the potting soil down to that part of the garden? If no, then can you let me know the reasons why not please?

No problem. Remember that bagged potting soil lacks beneficial bacteria, fungi etc, that natural soil contains, so blend it with your garden soil.

I ran out of garden soil when I needed to pot a hydrangea. I wasn't about to buy more for one plant though, so I used some potting mix and mixed it in with the clay.

Andy2019 said:I have one extra potting soil bag and a part of my garden needs some soil. Is it okay if I put the potting soil down to that part of the garden? If no, then can you let me know the reasons why not please?

Yes, parts of my garden have so much mixed in, from neighbors flower pots he tosses in the fall, that the ground is brown, which sticks out in the other wise black soil.

potting soil into the garden is ALWAYS good
Garden soil into a pot is NEVER good.

Potting soil is almost dirt free- its high drainage, fluffy. Good quality potting soil is moisture neutral, typically its mostly pearlite and peatmoss.

Dirt has things like clay- that holds water and rots roots or sand that drains so fast plants cant uptake the moisture they need, which you can get away with a a large surface area- like a 200+ sq ft garden, but contain it in a gallon pot, eghh- death sentence.

Yes that's completely fine! My usual procedure in the spring is to use the old potting soil in the garden where the beds need a top up, then replenish the containers with fresh potting soil.

Just be sure as someone else mentioned, to mix it in with your existing garden soil.