Hi @sau1,
Thank you for your question about increasing the depth and height of your garden bed.
There are a few things you should consider before altering this garden bed. If any height is added, you will need to protect the fence as it is not designed to act as a retaining structure and will not hold up well to the consistent moisture it will experience if acting as a garden bed.
If you're expanding the bed, consider building a timber sleeper bed where sleepers are used to separate the soil from the fence. Check out How To Build a Raised Garden Bed With Sleepers for some guidance.
Expanding the garden bed would mean first removing the bush on the left side. You can use a post-hole shovel to remove this plant. Use your post-hole shovel to dig around the plant, starting at least 30cm from the trunk and digging down around 30-45cm to preserve the root ball. It can then be placed in a temporary pot such as an Ezy Storage 60L Round Flexi Tub while the garden bed is altered. I wouldn't call this bush mature, but the principles described in How To Move An Advanced Or Mature Tree will apply.
Once this bush is removed, you can dig up the edging and remove the stake which can be seen in the bottom right corner of your image.
You can then follow How To Build a Raised Garden Bed With Sleepers.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
