cities-skylines
Planting trees in Cities: Skylines is a bit of a nightmare. I keep planting all these trees but they're only planted one at a time.
Is there an easier method of planting trees that doesn't involve mindlessly spam clicking an area until there's no more room for trees?
It may take some time to unlock it, but after you've passed enough milestones there will be a population info view in the info panel (top left button). It appears as a grey person pictogram, roughly halfway up on the left (5th up from the bottom as of version 1.4). This shows the current percentage that are unemployed.
Additionally, if you press Esc or click on the menu button at the top right, you can open the statistics menu where you can see your employment rate over time (after choosing the option from the tick list on the right).
You could try a frontage road running parallel to your large one way
This allows for numerous entry and exit points to the highway without making a zillion intersections on your main avenue. The frontage road also "filters" the traffic to closer to where they actually want to go instead of having them all go in and out at the same place.
Here's a screenshot of one I made in game:
It's a bit goofy because I didn't have room to run on both sides of the highway but flows very well.
Best Answer
Unfortunately, the only way to currently plant trees in the game is one-by-one.
There is a Tree Brush which will allow you to place multiple trees at a time, but it looks like the mod hasn't been updated since the latest patch (which broke a lot of mods), so it's not currently working. Since it's a mod, it will disable achievements. There is a mod to prevent mods from disabling achievements, but it appears to have broken with the latest patch as well.