i've seen lots of community posts where they have many rows of trees. How does one do this?

I crashed after about 6 or so rows of trees all firing at start of 26th wave. Was playing as Boy.

I'm not sure if it was too many trees, or too many meteor attacks, but my game froze and crashed so close to the end. I got this screenshot as it was crashing https://imgur.com/mBYgrXB

gardener can't get any upgrades, nor there is any description of what different types do

so i got boy first try on game so the i played it today. Everything was going my way when... On wave 20 the game crashed. mabey its that there was 7-8 lines of trees?