These are simple rows of trees to place alongside roads. I used the vanilla Oak tree so everyone can place additional trees by hand if the pieces don't add up to the same length as the road. Good for easier styling your farm lands.

They are parks and need to be placed on roads. But you can delete the roads afterwards if you like.

They have no costs, no amusement or touristic value, produce no garbage, need no energy or water.

They come in different lengths. 16 tiles, 8 tiles, 4 tiles and a 1 tile inner corner piece. There are also variants of the 16, 8 and 4 that are the same length but only use a 1x1 tile footprint.
I find the full length parks easier to place because you see where they end, but if the terrain is hard to build on these might come in handy.
They can also be used for outer corner pieces, where you can't build up to the end of the road.

Because these are parks and parks spawn seagulls, you might want to use a mod that disables them (=> [ARIS] Remove Seagulls).