In North Carolina you will have to go with one of the four state chosen insurance companies (STATE POOL), who charge what the state sets the rate at every year, around 40/100 dollars, unless you can find a private carrier to insure you. If you can get your Experience Rating below 1.00, you can probably get a good rate down around 25/100. Either way, you will have to audit every year.
The TCIA and ArborMax have teamed up to offer WC to members. There are some pre-qualifications, such as a CTSP on staff or Accreditation through the TCIA, but the program is tailored to Tree companies.
Amerisafe is another one out there that caters to the tree industry. Our rate has gotten under 25% and ER under .98, and audits and premiums are run monthly to avoid any surprises at the end of the year.
Be aware that splitting categories can be dicey. Clerical is easy to split off, and I pay less than 1% for them. Anyone and any work done for a job that can be classified as a tree job will be required to pay the Tree Worker WC rate, even if you split your crews into takedown and cleanup on different days. Stumpgrinding is classified as tree work, even if that is the only thing you do on a job, as well as raking, driving, blowing, etc. These regs are in the NCCI Scopes manual which defines industry classifications for the US. There are a few states that do not use the NCCI classification system. California, New Jersey, New York, Delaware, and Pennsylvania are states that have their own classification systems. Texas licenses much of the NCCI system, but makes significant variations in specific classification rules. Many other states have some "state special" classifications that can vary significantly from NCCI definitions for certain workplace exposures.