Q.what is better for tree hollies__pine straw mulch or mushroom soil
What is better for trees hollies- one year old mulch, or mushroom soil?
Certified GKH Gardening Expert
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