ash sucker trying to save

[wwtigraww]

So found this poor guy outside our estate during the summer, was keep getting cut by the grass cutting lads. so obviously I decided to save him
was no roots so I've used root powder and symbiot fungi powder then kept in high humidity for 4 weeks. now we have little leaves coming our and it's definitely alive!
question how long more would you keep it under plastic top or should I slowly start taking it off ?

 

[0soyoung]

Until the leaves have 'hardened', meaning fully opened, flat, and dark green like the big tree's leaves in late spring or summer. Oftentimes the buds on a cutting like this will break and the leaves will partially emerge and hand limply because there is no water due to the absence of roots. Keeping it tented will minimize water loss to transpiration, but the emergent leaves will be wimpy until roots have developed.

The leaves on the left side (as seen in the first pic) look like it is about there.