Paper/nms-patches/WorldGenMegaTreeProvider.patch

--- a/net/minecraft/server/WorldGenMegaTreeProvider.java
+++ b/net/minecraft/server/WorldGenMegaTreeProvider.java
@@ -2,6 +2,7 @@
 
 import java.util.Random;
 import javax.annotation.Nullable;
+import org.bukkit.TreeType; // CraftBukkit
 
 public abstract class WorldGenMegaTreeProvider extends WorldGenTreeProvider {
 
@@ -28,6 +29,15 @@
         if (worldgentreeabstract == null) {
             return false;
         } else {
+            // CraftBukkit start
+            if (worldgentreeabstract instanceof WorldGenJungleTree) {
+                BlockSapling.treeType = TreeType.JUNGLE;
+            } else if (worldgentreeabstract instanceof WorldGenMegaTree) {
+                BlockSapling.treeType = TreeType.MEGA_REDWOOD;
+            } else {
+                throw new IllegalArgumentException("Unknown tree generator " + worldgentreeabstract);
+            }
+            // CraftBukkit end
             IBlockData iblockdata1 = Blocks.AIR.getBlockData();
 
             generatoraccess.setTypeAndData(blockposition.a(i, 0, j), iblockdata1, 4);