--- a/src/tree_cmd.cpp
+++ b/src/tree_cmd.cpp
@@ -336,7 +336,7 @@
 /** Plant a tree.
  * @param tile start tile of area-drag of tree plantation
  * @param flags type of operation
- * @param p1 tree type, -1 means random.
+ * @param p1 tree type, TREE_INVALID means random.
  * @param p2 end tile of area-drag
  * @param text unused
  * @return the cost of this operation or an error
@@ -345,10 +345,11 @@
 {
 	StringID msg = INVALID_STRING_ID;
 	CommandCost cost(EXPENSES_OTHER);
+	const byte tree_to_plant = GB(p1, 0, 8); // We cannot use Extract as min and max are climate specific.
 
 	if (p2 >= MapSize()) return CMD_ERROR;
-	/* Check the tree type. It can be random or some valid value within the current climate */
-	if (p1 != UINT_MAX && p1 - _tree_base_by_landscape[_settings_game.game_creation.landscape] >= _tree_count_by_landscape[_settings_game.game_creation.landscape]) return CMD_ERROR;
+	/* Check the tree type within the current climate */
+	if (tree_to_plant != TREE_INVALID && !IsInsideBS(tree_to_plant, _tree_base_by_landscape[_settings_game.game_creation.landscape], _tree_count_by_landscape[_settings_game.game_creation.landscape])) return CMD_ERROR;
 
 	TileArea ta(tile, p2);
 	TILE_AREA_LOOP(tile, ta) {
@@ -401,9 +402,7 @@
 				}
 
 				if (flags & DC_EXEC) {
-					TreeType treetype;
-
-					treetype = (TreeType)p1;
+					TreeType treetype = (TreeType)tree_to_plant;
 					if (treetype == TREE_INVALID) {
 						treetype = GetRandomTreeType(tile, GB(Random(), 24, 8));
 						if (treetype == TREE_INVALID) treetype = TREE_CACTUS;

--- a/src/tree_gui.cpp
+++ b/src/tree_gui.cpp
@@ -18,6 +18,7 @@
 #include "company_base.h"
 #include "command_func.h"
 #include "sound_func.h"
+#include "tree_map.h"
 
 #include "table/sprites.h"
 #include "table/strings.h"
@@ -50,7 +51,7 @@
 {
 	uint16 base;        ///< Base tree number used for drawing the window.
 	uint16 count;       ///< Number of different trees available.
-	uint tree_to_plant; ///< Tree number to plant, \c UINT_MAX for a random tree.
+	TreeType tree_to_plant; ///< Tree number to plant, \c TREE_INVALID for a random tree.
 
 public:
 	BuildTreesWindow(const WindowDesc *desc, WindowNumber window_number) : Window()
@@ -105,13 +106,13 @@
 				if (widget - BTW_TYPE_11 >= this->count) break;
 
 				if (HandlePlacePushButton(this, widget, SPR_CURSOR_TREE, HT_RECT, NULL)) {
-					this->tree_to_plant = this->base + widget - BTW_TYPE_11;
+					this->tree_to_plant = (TreeType)(this->base + widget - BTW_TYPE_11);
 				}
 				break;
 
 			case BTW_TYPE_RANDOM: // tree of random type.
 				if (HandlePlacePushButton(this, BTW_TYPE_RANDOM, SPR_CURSOR_TREE, HT_RECT, NULL)) {
-					this->tree_to_plant = UINT_MAX;
+					this->tree_to_plant = TREE_INVALID;
 				}
 				break;
 

--- a/src/tree_map.h
+++ b/src/tree_map.h
@@ -22,17 +22,15 @@
  * offsets from the grfs files. These points to the start of
  * the tree list for a landscape. See the TREE_COUNT_* enumerations
  * for the amount of different trees for a specific landscape.
- *
- * @note TREE_INVALID may be 0xFF according to the coding style, not -1 (Progman)
  */
 enum TreeType {
-	TREE_INVALID      = -1,   ///< An invalid tree
 	TREE_TEMPERATE    = 0x00, ///< temperate tree
 	TREE_SUB_ARCTIC   = 0x0C, ///< tree on a sub_arctic landscape
 	TREE_RAINFOREST   = 0x14, ///< tree on the 'green part' on a sub-tropical map
 	TREE_CACTUS       = 0x1B, ///< a catus for the 'desert part' on a sub-tropical map
 	TREE_SUB_TROPICAL = 0x1C, ///< tree on a sub-tropical map, non-rainforest, non-desert
 	TREE_TOYLAND      = 0x20, ///< tree on a toyland map
+	TREE_INVALID      = 0xFF, ///< An invalid tree
 };
 
 /**