Where are you? Looks like something was eating them, in my world that might be slugs or caterpillars.

I live in Seattle. The gardenia is in a planter inside. No bug or mold is visible and the plant is shining green and still producing new shoots. The same thing happened last year. I trimmed the Bush severely and it was fine. Any guess?

Thank you.

Have you looked after dark? Have you checked the underside of the pot?

Slugs may be the culprit. They'll hide in the soil in the daytime.

I am pretty sure it's not caterpillars or slugs. Those holes you see were not eaten. They were spots dried up, withered, fall off, without losing green colors. The photo shows the fragments fall off leaving holes and tears. They are not eaten and no bug drops are found front of back of the leaves.

Do you have a cat?

Ime slugs and snails eat between leaf veins, not across them, and prefer softer foliage. This doesn't look like slug damage to me.

I'm concerned you may have a pet taking bites, or a caterpillar of some kind in your house. I know you aren't convinced but those are chewed places even if not swallowed - which leads me to wonder 'pet'.

Some of the photos make it look like caterpillar damage, and some of the photos look like tears. Since you're not seeing caterpillars, I suppose it could be weevils doing the damage. Many years ago my sister gave me a large potted plant and during winter I would see parts of leaves eaten on the plant. It took two winters of damage but I eventually found the culprit was some weevils. They are also more easily found at night!

eta: you have said they are dry spots that eventually fall off. How about showing one of those dry spots?