Eclipse is dumb and wasn't including these two files for some reason.

src/main/java/com/gmail/nossr50/skills/herbalism/GreenTerraTimer.java

@@ -0,0 +1,46 @@
+package com.gmail.nossr50.skills.herbalism;
+
+import org.bukkit.CropState;
+import org.bukkit.block.BlockState;
+import org.bukkit.material.CocoaPlant;
+import org.bukkit.material.CocoaPlant.CocoaPlantSize;
+
+/**
+ * Convert plants affected by the Green Terra ability.
+ *
+ * @param blockState The {@link BlockState} to check ability activation for
+ */
+public class GreenTerraTimer implements Runnable {
+    private BlockState blockState;
+
+    public GreenTerraTimer(BlockState blockState) {
+        this.blockState = blockState;
+    }
+
+    @Override
+    public void run() {
+        switch (blockState.getType()) {
+        case CROPS:
+        case CARROT:
+        case POTATO:
+            blockState.setRawData(CropState.MEDIUM.getData());
+            blockState.update(true);
+            return;
+
+        case NETHER_WARTS:
+            blockState.setRawData((byte) 0x2);
+            blockState.update(true);
+            return;
+
+        case COCOA:
+            CocoaPlant plant = (CocoaPlant) blockState.getData();
+            plant.setSize(CocoaPlantSize.MEDIUM);
+            blockState.setData(plant);
+            blockState.update(true);
+            return;
+
+        default:
+            return;
+        }
+    }
+}

src/main/java/com/gmail/nossr50/skills/herbalism/GreenThumbTimer.java

@@ -0,0 +1,64 @@
+package com.gmail.nossr50.skills.herbalism;
+
+import org.bukkit.block.BlockState;
+import org.bukkit.material.CocoaPlant;
+import org.bukkit.material.CocoaPlant.CocoaPlantSize;
+
+/**
+ * Convert plants affected by the Green Thumb ability.
+ *
+ * @param blockState The {@link BlockState} to check ability activation for
+ * @param skillLevel The player's Herbalism skill level
+ */
+public class GreenThumbTimer implements Runnable {
+    private BlockState blockState;
+    private int skillLevel;
+
+    public GreenThumbTimer(BlockState blockState, int skillLevel) {
+        this.blockState = blockState;
+        this.skillLevel = skillLevel;
+    }
+
+    @Override
+    public void run() {
+        int greenThumbStage = Math.min(Math.min(skillLevel, Herbalism.greenThumbStageMaxLevel) / Herbalism.greenThumbStageChangeLevel, 4);
+
+        switch(blockState.getType()) {
+        case CROPS:
+        case CARROT:
+        case POTATO:
+            blockState.setRawData((byte) greenThumbStage);
+            blockState.update(true);
+            return;
+
+        case NETHER_WARTS:
+            if (greenThumbStage > 2) {
+                blockState.setRawData((byte) 0x2);
+            }
+            else if (greenThumbStage == 2) {
+                blockState.setRawData((byte) 0x1);
+            }
+            else {
+                blockState.setRawData((byte) 0x0);
+            }
+            blockState.update(true);
+            return;
+
+        case COCOA:
+            CocoaPlant plant = (CocoaPlant) blockState.getData();
+
+            if (greenThumbStage > 1) {
+                plant.setSize(CocoaPlantSize.MEDIUM);
+            }
+            else {
+                plant.setSize(CocoaPlantSize.SMALL);
+            }
+            blockState.setData(plant);
+            blockState.update(true);
+            return;
+
+        default:
+            return;
+        }
+    }
+}