The route I take (Requires Crimsonwood Map):
Start in Dead Man's Gorge, at the top left (use the bottom right gate to get up if you're on the floor).
Go through it to Forgotten Path (far right).
Change channel, you end up at the centre.
Go through the portal to Crossroads (2), top.
Jump down, take the far left portal.
Run across Haunted Hill, enter the gate.
Forgotten Path has 1 tree near the middle portal.
Crossroads (2) has 3 on top, 1 middle, 3 bottom.
Haunted Hill has 2 easily accessable, on the first level of raised platforms, so as you go left just jump up to them.
When I get through 19 channels of this, I was doing TP4-TP5-Crossroads(3):
Enter TP4 far left, go to far right portal.
Go 2 portals left in TP5 (also check for additional tree at far left maybe)
At Crossroads 3, kill anything, drop down, change channel.
Enter 2nd from right portal to end up at the far left of TP4.
TP4+TP5 have 4 trees. Crossroads 3 has again.
There's a potential loop of Crossroads 1, TP3, and Phantom Road, however I'm not sure how many trees are in Phantom Road (the upper left portal in Phantom Road takes you to the top of Crossroads 1 without having to use teleport).
Start in Dead Man's Gorge, at the top left (use the bottom right gate to get up if you're on the floor).
Go through it to Forgotten Path (far right).
Change channel, you end up at the centre.
Go through the portal to Crossroads (2), top.
Jump down, take the far left portal.
Run across Haunted Hill, enter the gate.
Forgotten Path has 1 tree near the middle portal.
Crossroads (2) has 3 on top, 1 middle, 3 bottom.
Haunted Hill has 2 easily accessable, on the first level of raised platforms, so as you go left just jump up to them.
When I get through 19 channels of this, I was doing TP4-TP5-Crossroads(3):
Enter TP4 far left, go to far right portal.
Go 2 portals left in TP5 (also check for additional tree at far left maybe)
At Crossroads 3, kill anything, drop down, change channel.
Enter 2nd from right portal to end up at the far left of TP4.
TP4+TP5 have 4 trees. Crossroads 3 has again.
There's a potential loop of Crossroads 1, TP3, and Phantom Road, however I'm not sure how many trees are in Phantom Road (the upper left portal in Phantom Road takes you to the top of Crossroads 1 without having to use teleport).