Plant Nursery In Space?

It seems to me that in order to have a functioning biosphere,
biotorus, or biocylinder in orbit we'll have to nurture the plant
life long before the habitat it completed.

The more I think about it, the more that I'm convinced that before
any work starts on the habitat itself, we'll have to construct a
large structure to be used as a plant nursery. It'll be packed with
hundreds of acres of growing plants and trees. It'll have to be
designed to allow for tree growth over the 10-25 year construction
timeline for the habitat.

It'll be interesting to see how a 25 year old tree will be removed
from the nursery, transported across space, brought into the
habitat, and now under gravity, transported to its ultimate location
and re-planted. This may call for a whole new profession; astro-
botanical transportation engineer:)

Of course all of the above is premised on the assumption that we'll
try to have a bio-environment regulate the habitat, rather than
SOLELY air scrubbers and other mechanical means. I don't see how we
can start a functioning bio-environment from scratch. A little
sapling of a tree is nowhere near as efficient a CO2 scrubber as a
substantial tree. The biomass will have to come from somewhere.
Better to grow it in orbit than to haul it all from earth. Better to
launch the seeds or little shoots in a shuttle launch, rather than
trying to figure out how to send trees into orbit:)

Now considering that trees are made from the carbon in the air,
we'll have to have a steady supply of carbon which we'll combine
with the O2 that is a byproduct of lunar material extraction, thus
forming CO2. We'll cycle this through the nursery, and extract the
O2 again. Add more carbon and start the cycle again.

It's amazing to think that the mass of a tree is primarily made by
extracting the carbon from the air. WOW.