Good day, about 4 years ago, I did a test using UPM inside 3 of my large container trees. They were, Galbun, Panachee, and Hardy Chicago. I like UPM. Years ago it was a hot topic! Well I found a supplier and tested it against plain old compost. Hands down, all trees did better in the compost. After repoting 20+ figs (27g 22 in diameter) over the weekend.....Here are my findings..
| UPM | UPM Comment | Mushroom compost Comment | Mushroom compost Comment |
Wicking | Excellent | too wet -- uses little water first—on a 90 degree day—you have to water twice a day. | Great | takes time to wick up—you have to water it in layers when you build your pot or your tree will go into shock. Otherwise it could take days to wick up. |
Drainage | great | holds too much water for figs | Great | Just don’t block the drain hole |
Water Holding | Hold little water | UPM holds little water but more water is needed once it starts to pull. | Hold a lot of water | Can go days without watering due to the density of the dirt |
Pros | Very light weight | Very Heavy |
Con | Ants love it and will nest in the bottom of your pot—often have to water more over time | To move a 27g SIP that’s 22 inches in diameter is very difficult. Use dunnage or build it only in the spot it will remain for 3 years. |
I will not use UPM again. For me, I will be using straight mushroom compost. If you build it right....a tree in a 27g - 22inch diameter pot at 85 degrees only needs watering once a week. But that water reserevoir hold 5 gallons or more of water!
Hopes this helps!