Wondering how late in the spring I can begin the process before I miss out?

Which process, air layer or graft? And for which species?
Grafting normally is done before plants leaf out. Airlayering after the first leaves show, untill late spring.

Air layering juniper /maple, and thank you that makes sense

Hi, it really depends on the spicies when you can start but mid spring to early summer is the general rule of thumb.

Hope this helps

Air layer for maple you can place as soon as they start growing. I would not start them after june anymore.. this allows for separation in summer, with time left to establih for winter.

Juniper may take long to grow roots. I think you could start them yearround, but ideallyy early growing season.