My fiance bought me this Olive bonsai 2 years ago for Christmas from a bonsai shop nearby. This specific tree is now 14 years old, and it appears to be getting more and more sick over the last 6 months or so. I water it about once a week, and spritz fertilizer water on it around that same time. I know grow lights are not a great solution, but we really don't have a place in our house that gets full sun all day long, so we keep the grow lights going over it during daytime hours. Over the last few weeks, I have been taking it outside for direct sunlight, but that has seemed to make it worse. The leaves are wilting, and some have been falling off. Any help would be greatly appreciated!!

Hello.

You don't place it outside during day, like a treatment, and then back in... Trees don't have legs to go out and in, it weakened because it's inside... Our house conditions are not propper to plants, they'll just survive for some time...

It's been unseasonably hot this year, so I haven't been putting it outside much. Can Olive trees handle temps ranging from 90-100+ F? I feel like every time I put it outside, it gets more wilted.

The problem doesn't seem to be the temperature itself, but the stress on being in a colder place, and going into a hotter place, than changing it back again...

"Quote from oliveoiltime.com : Olive trees can safely withstand 35 – 36 °C (95°-96.8°F)"
If it's getting hotter than that, I would consider a placement where you can avoid the peak sun hours (like other trees' shadow, or net), but not keep moving around.

That being said, Idk if it still being able to get better, I would place it where it doesn't take much direct sun, but a good amount of indirect light (natural light), leave it there and hope for the best...

They say that that they need to be re-potted every 2-3 years for younger trees. Its been 2 years since I got it. Do you think that could help? I was considering taking it back to the place we got it from, and having them re-pot it. I would just hate to lose 14 years of growth

Do not repot
Do not fertilise
Do not place it inside ( unless it freezes, then you place it in an unheated frostfree place, NOT in your heated house)
Do place it outside, for now in a shaded spot. Where do you think olives live? They can stand high temperatures, but not the deadly environment of your house.
Water thoroughly with a watering can or garden hose untill water spills from the drainage hole
Hope- olives are strong but it might be too late for this one.

Yes, the soil may be broken down by now, but it's not quite recommended to repot unhealthy trees.

I've seen people sliding plants to the ground as a last attempt. But I won't recommend that.

There are people here more experienced than me and olive owners that could tell you more.