Trying to make something realistically appear behind trees and plants.

Try duplicating the layer and adding a layer mask to the top layer. Then add the content you want between the layers. Here's how:

1. Select the layer with the photo
2. Use Ctrl (Windows) / Command (macOS) + J or go to Layer > New > Layer via Copy to duplicate the layer
3. With the top layer selected, click the layer mask icon at the bottom of the Layers panel or go to Layer > Layer Mask > Reveal All
4. With the layer mask selected, select the Brush tool, use the brush settings in the Options bar (Window > Options) to select a brush about the width of the palm tree, set the hardness to about 50%, set the foreground and background colors to the default (press D), and press X when you want to switch them
5. Turn off the visibility of the layer below by clicking on the eyeball
6. With black as the foreground draw on the layer mask to hide the palm tree (hide the palm tree so that you can see what you're masking)
7. When the portion of the tree is hidden where you'll be placing your other content, make sure the layer mask icon in the Layers panel is selected and invert the layer mask (Ctrl / Command + I or go to Image > Adjustments > Invert)
8. Add the content that you want to place behind the tree
9. Move that layer between the image and the masked image layers
10. Turn the visibility of the lower image layer back on
11. When the section of the palm tree is 

Have you tried selecting the area and then using Generative Fill to have AI create whatever it is you want behind the palm tree?