Q.Staghorn ferns
I saw a staghorn at the local nursery with a maidenhair fern growing up from the inner circle. I would like to know whether this is safe for the plant and if they are symbiotic.
A Staghorn fern would not be symbiotic. The combination that you mention seeing in the garden center was likely created for visual interest, but the Maidenhair Fern has a completely different growing condition than the Staghorn. They would not thrive together for any length of time.
There has been a big popularity in the art of Kokedama moss ball plantings. This pairing seems to me to be a representation of this technique.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/foliage/staghorn-fern/staghorn-fern-information.htm
https://www.gardeningknowhow.com/ornamental/foliage/maidenhair-fern/maidenhair-fern-care.htm
https://www.gardeningknowhow.com/garden-how-to/projects/making-kokedama-moss-balls.htm
