Not sure if there are many/any podcasts about digital gardens and tangential topics, but I’ve started a tag on Huffduffer for those who’d like it for discovery or adding those they find themselves:
If you find a podcast with some discussion about the topic, feel free to use Huffduffer’s bookmarklet to add it to the public list. This should also work with YouTube videos and it will convert the video into audio and save it to the list.

It has an RSS feed for subscribing if you like.