Index: src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java
===================================================================
--- src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java	(revision 4280)
+++ src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java	(working copy)
@@ -68,7 +68,7 @@
             return;
 
         test = w.get("natural");
-        if (test != null && !"coastline".equals(test) && !"cliff".equals(test)) {
+        if (test != null && !"coastline".equals(test) && !"cliff".equals(test) && !"tree_row".equals(test)) {
             set(1101, marktr("natural type {0}"), test);
         }
         test = w.get("landuse");