diff --git a/packages/farm/src/resources/decorators/room.js b/packages/farm/src/resources/decorators/room.js
index 31f37d4..45768dd 100644
--- a/packages/farm/src/resources/decorators/room.js
+++ b/packages/farm/src/resources/decorators/room.js
@@ -7,6 +7,7 @@ import {
 import Renderable from './room/renderable';
 
 const DIRT = 6;
+const GRASS = [1, 2, 3, 4, 10, 11, 12];
 const TILLED = 7;
 
 export default (Room) => class FarmableRoom extends Room {
@@ -92,7 +93,10 @@ export default (Room) => class FarmableRoom extends Room {
 
   mayPrepareSoilAt(target) {
     const [tiles] = this.tiles;
-    return DIRT === tiles.tileAt(target);
+    return (
+      DIRT === tiles.tileAt(target)
+      || -1 !== GRASS.indexOf(tiles.tileAt(target))
+    );
   }
 
   maySowAt(center) {
@@ -117,7 +121,7 @@ export default (Room) => class FarmableRoom extends Room {
   prepareSoilAt(target) {
     if ('client' !== process.env.SIDE) {
       const [tiles] = this.tiles;
-      tiles.setTileAt(target, TILLED);
+      tiles.setTileAt(target, DIRT === tiles.tileAt(target) ? TILLED : DIRT);
       this.adjustWaterAt(target, 0);
     }
   }