I just checked with the contact of the export company in China last night, they had submitted the tree export application to the custom.
If no inspection from custom needed, likely in three days, they can get the permission from custom, otherwise, it will take about a week.
They they can start to arrange air freight, and normally two days before the shipping, they start to pull up trees from tree fields.
Also they are considering using the coconut fiber and SAP( super absorbent polymer) as packing material to keep roots and tree moisturized during the shipping. It is a very solid export company.
I interviewed a couple of custom broker companies, and finally decided to use Steven N, a very experienced guy, as my custom clearance power attorney, his office is nearby SFO.