Hi @catalinux777 - welcome to the farmOS forum!
There are a few different approaches - depending on how you want to manage things. You could put them in as individual assets if you want, like you describe. This is useful if you want to track each tree individually, and have separate logs associated with each (eg: separate observations, inputs, harvests, etc).
Another approach is to have a single asset that represents all trees of a certain species - and maybe even limited to a certain area (eg: “Oak trees in north field”). In this arrangement you’re tracking all of them as a single asset (a single “management unit”) and all logs you record apply to all the trees in that unit. This single asset would have at least one log that defines it’s location (eg: a transplanting log, observation log, etc - whatever makes sense).
I assume you are using farmOS 1.x. In farmOS 2.x (currently in development), it’s possible to define assets with “intrinsic geometry” - which means you don’t need to record a movement log to define where they are. This might make mapping of trees a bit easier for you - if you don’t need an explicit “event” recorded.
Another feature we are talking about building in 2.x is a way to view the geometry of all logs (filterable) associated with an asset. So, for example, you could have an asset that represents a certain type of tree, and then multiple observation logs that mark points on the map where you’ve observed this kind of tree. These points would not show on the asset’s “current geometry” (because they wouldn’t technically be “movement logs”) but you would be able to pull up a map of all the observations you’ve made of this asset, which would give you the same information. We haven’t built this yet, but it’s something we’re talking about… I think it would be useful for a lot of different things.
Hope that helps!