what is better for tree hollies__pine straw mulch or mushroom soil

Question

What is better for trees hollies- one year old mulch, or mushroom soil?

Answer 1

Pine straw mulch is great for hollies, since it will acidify the soil over time, which hollies prefer, and also provide the other benefits of mulch:
https://www.gardeningknowhow.com/garden-how-to/mulch/pine-straw-for-mulch.htm

Mushroom compost tends to make soil more alkaline, so it's not as good for hollies, unless your soil is already ecxessively acidic:
https://www.rhs.org.uk/advice/profile?PID=294

However, adding some kind of compost or fertilizer in addition to mulch is a good idea:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/fertilizing-holly-bushes.htm