It comes untreated so you have to paint or stain it after installation if you want it to last and provide maximum weather resistance.
Should you seal the bottom of siding.
Holes occur over time when seals crack around plumbing fixtures on your siding allowing mice entrance into your home.
The bottom of the starter strip the part the bottom panel hooks on to should be at least 1 in.
Caulking the bottom.
By sealing gaps in your walls and siding you can successfully secure your home from outdoor pests.
Also avoid caulking tongue and groove siding boards together.
I would be hesitant to seal the siding to the foundation.
Below the top of the foundation but the lower the vinyl siding is installed the better.
How to seal plywood siding.
The sheets are grooved so that the edges will seal when you nail them together but you need to install flashing caulking and trim along the top and bottom edges and around windows and doors to keep water out.
Plywood siding is typically made of fir or cedar and usually has vertical grooves that give it the appearance of planking.
While my experience is more with vinyl siding sealing the siding to the foundation would deny any moisture that developed behind the siding from driving rain between seams in the siding condensation behind the siding ect an exit at the bottom.
A full seal is important because any space that is missing sealant is more susceptible to water damage and chemical bleeding.
If you prefer to caulk before painting you should still paint the cut ends first.
While paint does tend to somewhat glue these pieces together caulking them is never advised and can cause permanent damage.
It protects the sheathing from rain snow and pests.
After the paint dries apply caulk and then paint the rest of the siding.
Inexpensive and simple to do sealing your siding only requires a little time to locate the cracks.
For best results seal before applying the siding to the wall.
This way you can completely seal the cedar front to back top to bottom and around all edges.