When the soil is dry—below the surface where the roots are. Depending on the age and species, they can tolerate dryer or deeper soil moisture but in general most of the time when it’s dry in the top few inches it won’t hurt to water them unless you’re dealing with a desert species. Make sure to water deeply and over a wide area, avoiding the area immediately around the trunk unless the tree was recently planted.

[–] toaster@slrpnk.net 2 points 9 months ago (1 children)

This is very useful information, thank you!

[–] LibertyLizard@slrpnk.net 2 points 9 months ago* (last edited 9 months ago)

No problem. Most cities have a local tree planting NGO so that can be a good place to look for local advice if this is something that interests you. I have planted many trees in my own community and have found it incredibly rewarding.