The letter from Simon Hodgson follows concerns within the sector over the control and supply of seed to growers.
In his letter Hodgson said he is taking the opportunity to "reassure people who do business with us that we intend to continue to work with the sector honestly, openly and fairly".
Referring to the Forestry Commission's nurseries he said their purpose is to: "Supply our own forest operations and that applies to the new investment in our Delamere Nursery."
He added: "We have developed seed orchards and continue to collect seed for our own and wider sector use. This year to date we have supplied over 430kg of improved Sitka spruce seed to external nurseries. It is in our interest to have UK forests using high quality seed to grow high quality trees that will provide the best timber. Like the rest of the sector we also buy seeds and plants from other providers when we cannot supply ourselves.
"We continue to provide seed and plants to other parts of the Forestry Commission. Our supply arrangements to Natural Resources Wales continue to 2019/20 and while their intentions with regard to their future supply of trees are at this point unclear, I am certain if there is an open tender for plants it will be according to strict public procurement rules.
"Forest Enterprise England intends to maintain business-like relationships with the private nursery sector to the benefit of UK forestry and timber businesses."