diff --git a/dat/themerms.lua b/dat/themerms.lua
index 7d5a73860..6aff95286 100644
--- a/dat/themerms.lua
+++ b/dat/themerms.lua
@@ -1071,7 +1071,10 @@ end
 -- postprocess callback: turn room walls into trees
 function make_garden_walls(data)
    local sel = data.sel:grow();
+   -- change walls to trees
    des.replace_terrain({ selection = sel, fromterrain="w", toterrain = "T" });
+   -- update secret doors; attempting to change to AIR will set arboreal flag
+   des.replace_terrain({ selection = sel, fromterrain="S", toterrain = "A" });
 end
 
 -- postprocess callback: make a trap
diff --git a/include/rm.h b/include/rm.h
index 001414a10..f0382870f 100644
--- a/include/rm.h
+++ b/include/rm.h
@@ -219,6 +219,9 @@ struct rm {
 #define D_LOCKED  0x08
 
 #define D_TRAPPED 0x10
+/* secret doors aren't trapped or nonpasswall; overload D_TRAPPED and
+   W_NONPASSWALL for 'arboreal' secret doors (in garden theme room) */
+#define D_ARBOREAL D_TRAPPED
 #define D_SECRET  0x20 /* only used by sp_lev.c, NOT in rm-struct */
 
 /*
diff --git a/src/detect.c b/src/detect.c
index 0d1de0c83..89476dc88 100644
--- a/src/detect.c
+++ b/src/detect.c
@@ -1588,7 +1588,7 @@ do_vicinity_map(
 void
 cvt_sdoor_to_door(struct rm *lev)
 {
-    int newmask = lev->doormask & ~WM_MASK;
+    int newmask = lev->doormask & ~(WM_MASK | D_ARBOREAL);
 
     if (Is_rogue_level(&u.uz)) {
         /* rogue didn't have doors, only doorways */
diff --git a/src/display.c b/src/display.c
index 71c77bb87..716bdf2b8 100644
--- a/src/display.c
+++ b/src/display.c
@@ -2289,6 +2289,13 @@ back_to_glyph(coordxy x, coordxy y)
     case CORR:
         idx = (ptr->waslit || flags.lit_corridor) ? S_litcorr : S_corr;
         break;
+    case SDOOR:
+        if ((ptr->doormask & D_ARBOREAL) != 0) {
+            idx = S_tree;
+            break;
+        }
+        FALLTHROUGH;
+        /*FALLTHRU*/
     case HWALL:
     case VWALL:
     case TLCORNER:
@@ -2300,7 +2307,6 @@ back_to_glyph(coordxy x, coordxy y)
     case TDWALL:
     case TLWALL:
     case TRWALL:
-    case SDOOR:
         idx = ptr->seenv ? wall_angle(ptr) : S_stone;
         break;
     case DOOR:
@@ -3579,6 +3585,10 @@ wall_angle(struct rm *lev)
         break;
 
     case SDOOR:
+        if ((lev->doormask & D_ARBOREAL) != 0) {
+            idx = S_tree;
+            break;
+        }
         if (lev->horizontal)
             goto horiz;
         FALLTHROUGH;
diff --git a/src/mkmaze.c b/src/mkmaze.c
index df83d2136..903330cf3 100644
--- a/src/mkmaze.c
+++ b/src/mkmaze.c
@@ -76,8 +76,16 @@ boolean
 set_levltyp(coordxy x, coordxy y, schar newtyp)
 {
     if (isok(x, y) && newtyp >= STONE && newtyp < MAX_TYPE) {
-        if (CAN_OVERWRITE_TERRAIN(levl[x][y].typ)) {
-            schar oldtyp = levl[x][y].typ;
+        schar oldtyp = levl[x][y].typ;
+
+        /* hack for secret doors in garden theme rooms */
+        if (oldtyp == SDOOR && newtyp == AIR) {
+            /* levl[][].typ stays SDOOR rather than change to AIR */
+            levl[x][y].doormask |= D_ARBOREAL;
+            return TRUE;
+        }
+
+        if (CAN_OVERWRITE_TERRAIN(oldtyp)) {
             /* typ==ICE || (typ==DRAWBRIDGE_UP && drawbridgemask==DB_ICE) */
             boolean was_ice = is_ice(x, y);