diff --git a/harvester/src/mapbox_tree_update.py b/harvester/src/mapbox_tree_update.py
index bc1a40c5..a51a1085 100644
--- a/harvester/src/mapbox_tree_update.py
+++ b/harvester/src/mapbox_tree_update.py
@@ -75,6 +75,16 @@ def generate_trees_csv(temp_dir, db_conn):
             """
         )
         trees = cur.fetchall()
+        trees = []
+
+        # Get all waterings that are included in the amount of waterings for the last 30 days
+        cur.execute(
+            """
+                SELECT * FROM trees_watered w WHERE w.timestamp >= CURRENT_DATE - INTERVAL '30 days' AND DATE_TRUNC('day', w.timestamp) < CURRENT_DATE;
+            """
+        )
+        trees_watered = cur.fetchall()
+
         logging.info(f"Creating trees.csv file for {len(trees)} trees...")
 
         # Build CSV file with all trees in it
@@ -109,7 +119,7 @@ def generate_trees_csv(temp_dir, db_conn):
         with open(trees_csv_full_path, "w") as out:
             out.write(trees_csv)
 
-        return trees_csv_full_path
+        return (trees_csv_full_path, trees_watered)
 
 
 def update_mapbox_tree_layer(
@@ -125,7 +135,7 @@ def update_mapbox_tree_layer(
 
     with tempfile.TemporaryDirectory() as temp_dir:
         # Generate trees.csv from trees in database
-        trees_csv_full_path = generate_trees_csv(temp_dir, db_conn)
+        (trees_csv_full_path, trees_watered) = generate_trees_csv(temp_dir, db_conn)
 
         # Preprocess trees.csv with tippecanoe
         trees_preprocessed_full_path = preprocess_trees_csv(
@@ -164,3 +174,28 @@ def update_mapbox_tree_layer(
 
         if tileset_creation_error is not None:
             logging.error("Could not create Mapbox tileset")
+
+        return trees_watered
+
+
+def update_tree_waterings(trees_watered, db_conn):
+    print(f"Set included_in_map_layer = TRUE for {len(trees_watered)} watered trees...")
+    tree_ids = [tree_watered[4] for tree_watered in trees_watered]
+    with db_conn.cursor() as cur:
+        # Set included_in_map_layer = FALSE for all waterings
+        cur.execute(
+            """
+                UPDATE trees_watered SET included_in_map_layer = FALSE WHERE TRUE;
+            """,
+            (tree_ids,),
+        )
+        db_conn.commit()
+
+        # Set included_in_map_layer = FALSE for the waterings that are included in this round of the harvester
+        cur.execute(
+            """
+                UPDATE trees_watered SET included_in_map_layer = TRUE WHERE id = ANY (%s);
+            """,
+            (tree_ids,),
+        )
+        db_conn.commit()
diff --git a/harvester/src/run_harvester.py b/harvester/src/run_harvester.py
index 9eceb3bd..f8201952 100644
--- a/harvester/src/run_harvester.py
+++ b/harvester/src/run_harvester.py
@@ -9,7 +9,7 @@
 from radolan_db_utils import (
     get_start_end_harvest_dates,
 )
-from mapbox_tree_update import update_mapbox_tree_layer
+from mapbox_tree_update import update_mapbox_tree_layer, update_tree_waterings
 
 # Set up logging
 logging.basicConfig()
@@ -79,7 +79,7 @@
 
 # Update Mapbox layer
 if not SKIP_MAPBOX:
-    update_mapbox_tree_layer(
+    trees_watered = update_mapbox_tree_layer(
         MAPBOX_USERNAME,
         MAPBOX_TOKEN,
         MAPBOX_TILESET,
@@ -89,3 +89,6 @@
         SUPABASE_SERVICE_ROLE_KEY,
         database_connection,
     )
+
+    # Update the tree waterings and flag the waterings which are now included in the mapbox layer with included_in_map_layer = TRUE
+    update_tree_waterings(trees_watered, database_connection)