diff --git a/cmd-choose-tree.c b/cmd-choose-tree.c
index 65c3ae0a..815c2a03 100644
--- a/cmd-choose-tree.c
+++ b/cmd-choose-tree.c
@@ -30,8 +30,8 @@ const struct cmd_entry cmd_choose_tree_entry = {
 	.name = "choose-tree",
 	.alias = NULL,
 
-	.args = { "F:f:NO:st:w", 0, 1 },
-	.usage = "[-Nsw] [-F format] [-f filter] [-O sort-order] "
+	.args = { "F:Gf:NO:st:w", 0, 1 },
+	.usage = "[-GNsw] [-F format] [-f filter] [-O sort-order] "
 	         CMD_TARGET_PANE_USAGE,
 
 	.target = { 't', CMD_FIND_PANE, 0 },
diff --git a/format.c b/format.c
index 04748a2f..46f1a522 100644
--- a/format.c
+++ b/format.c
@@ -587,8 +587,35 @@ format_cb_pane_tabs(struct format_tree *ft, struct format_entry *fe)
 			evbuffer_add(buffer, ",", 1);
 		evbuffer_add_printf(buffer, "%u", i);
 	}
-	size = EVBUFFER_LENGTH(buffer);
-	xasprintf(&fe->value, "%.*s", size, EVBUFFER_DATA(buffer));
+	if ((size = EVBUFFER_LENGTH(buffer)) != 0)
+		xasprintf(&fe->value, "%.*s", size, EVBUFFER_DATA(buffer));
+	evbuffer_free(buffer);
+}
+
+/* Callback for session_group_list. */
+static void
+format_cb_session_group_list(struct format_tree *ft, struct format_entry *fe)
+{
+	struct session		*s = ft->s;
+	struct session_group	*sg;
+	struct session		*loop;
+	struct evbuffer		*buffer;
+	int			 size;
+
+	if (s == NULL)
+		return;
+	sg = session_group_contains(s);
+	if (sg == NULL)
+		return;
+
+	buffer = evbuffer_new();
+	TAILQ_FOREACH(loop, &sg->sessions, gentry) {
+		if (EVBUFFER_LENGTH(buffer) > 0)
+			evbuffer_add(buffer, ",", 1);
+		evbuffer_add_printf(buffer, "%s", loop->name);
+	}
+	if ((size = EVBUFFER_LENGTH(buffer)) != 0)
+		xasprintf(&fe->value, "%.*s", size, EVBUFFER_DATA(buffer));
 	evbuffer_free(buffer);
 }
 
@@ -781,8 +808,11 @@ format_find(struct format_tree *ft, const char *key, int modifiers)
 			found = s;
 			goto found;
 		}
-		if (fe->value == NULL && fe->cb != NULL)
+		if (fe->value == NULL && fe->cb != NULL) {
 			fe->cb(ft, fe);
+			if (fe->value == NULL)
+				fe->value = xstrdup("");
+		}
 		found = fe->value;
 		goto found;
 	}
@@ -1269,8 +1299,13 @@ format_defaults_session(struct format_tree *ft, struct session *s)
 
 	sg = session_group_contains(s);
 	format_add(ft, "session_grouped", "%d", sg != NULL);
-	if (sg != NULL)
+	if (sg != NULL) {
 		format_add(ft, "session_group", "%s", sg->name);
+		format_add(ft, "session_group_size", "%u",
+		    session_group_count (sg));
+		format_add_cb(ft, "session_group_list",
+		    format_cb_session_group_list);
+	}
 
 	format_add_tv(ft, "session_created", &s->creation_time);
 	format_add_tv(ft, "session_last_attached", &s->last_attached_time);
diff --git a/screen.c b/screen.c
index 4e234201..f6135b50 100644
--- a/screen.c
+++ b/screen.c
@@ -196,7 +196,8 @@ screen_resize(struct screen *s, u_int sx, u_int sy, int reflow)
 		 * is simpler and more reliable so let's do that.
 		 */
 		screen_reset_tabs(s);
-	}
+	} else
+		reflow = 0;
 
 	if (sy != screen_size_y(s))
 		screen_resize_y(s, sy);
diff --git a/session.c b/session.c
index 6143807c..5b17f085 100644
--- a/session.c
+++ b/session.c
@@ -38,10 +38,6 @@ static struct winlink *session_next_alert(struct winlink *);
 static struct winlink *session_previous_alert(struct winlink *);
 
 static void	session_group_remove(struct session *);
-static u_int	session_group_count(struct session_group *);
-static void	session_group_synchronize1(struct session *, struct session *);
-
-static u_int	session_group_count(struct session_group *);
 static void	session_group_synchronize1(struct session *, struct session *);
 
 RB_GENERATE(sessions, session, entry, session_cmp);
@@ -623,7 +619,7 @@ session_group_remove(struct session *s)
 }
 
 /* Count number of sessions in session group. */
-static u_int
+u_int
 session_group_count(struct session_group *sg)
 {
 	struct session	*s;
diff --git a/tmux.1 b/tmux.1
index 9a9e5d7a..3061790d 100644
--- a/tmux.1
+++ b/tmux.1
@@ -1432,7 +1432,7 @@ starts without the preview.
 This command works only if at least one client is attached.
 .It Xo
 .Ic choose-tree
-.Op Fl Nsw
+.Op Fl GNsw
 .Op Fl F Ar format
 .Op Fl f Ar filter
 .Op Fl O Ar sort-order
@@ -1488,6 +1488,9 @@ If a filter would lead to an empty list, it is ignored.
 specifies the format for each item in the tree.
 .Fl N
 starts without the preview.
+.Fl G
+includes all sessions in any session groups in the tree rather than only the
+first.
 This command works only if at least one client is attached.
 .It Xo
 .Ic display-panes
@@ -3715,6 +3718,8 @@ The following variables are available, where appropriate:
 .It Li "session_format" Ta "" Ta "1 if format is for a session (not assuming the current)"
 .It Li "session_last_attached" Ta "" Ta "Time session last attached"
 .It Li "session_group" Ta "" Ta "Name of session group"
+.It Li "session_group_size" Ta "" Ta "Size of session group"
+.It Li "session_group_list" Ta "" Ta "List of sessions in group"
 .It Li "session_grouped" Ta "" Ta "1 if session in a group"
 .It Li "session_height" Ta "" Ta "Height of session"
 .It Li "session_id" Ta "" Ta "Unique session ID"
diff --git a/tmux.h b/tmux.h
index 578fbb4d..b1d12361 100644
--- a/tmux.h
+++ b/tmux.h
@@ -2339,6 +2339,7 @@ struct session_group *session_group_new(const char *);
 void		 session_group_add(struct session_group *, struct session *);
 void		 session_group_synchronize_to(struct session *);
 void		 session_group_synchronize_from(struct session *);
+u_int		 session_group_count(struct session_group *);
 void		 session_renumber_windows(struct session *);
 
 /* utf8.c */
diff --git a/window-tree.c b/window-tree.c
index a58154b8..a1c511de 100644
--- a/window-tree.c
+++ b/window-tree.c
@@ -43,8 +43,10 @@ static void		 window_tree_key(struct window_pane *,
 			"#{?#{==:#{window_panes},1}, \"#{pane_title}\",}" \
 		"," \
 			"#{session_windows} windows" \
-			"#{?session_grouped, (group ,}" \
-	    		"#{session_group}#{?session_grouped,),}" \
+			"#{?session_grouped, " \
+				"(group #{session_group}: " \
+				"#{session_group_list})," \
+			"}" \
 			"#{?session_attached, (attached),}" \
 		"}" \
 	"}"
@@ -91,6 +93,7 @@ struct window_tree_modedata {
 	struct mode_tree_data		 *data;
 	char				 *format;
 	char				 *command;
+	int				  squash_groups;
 
 	struct window_tree_itemdata	**item_list;
 	u_int				  item_size;
@@ -394,8 +397,11 @@ window_tree_build(void *modedata, u_int sort_type, uint64_t *tag,
 {
 	struct window_tree_modedata	*data = modedata;
 	struct session			*s, **l;
+	struct session_group		*sg, *current;
 	u_int				 n, i;
 
+	current = session_group_contains(data->fs.s);
+
 	for (i = 0; i < data->item_size; i++)
 		window_tree_free_item(data->item_list[i]);
 	free(data->item_list);
@@ -405,6 +411,12 @@ window_tree_build(void *modedata, u_int sort_type, uint64_t *tag,
 	l = NULL;
 	n = 0;
 	RB_FOREACH(s, sessions, &sessions) {
+		if (data->squash_groups &&
+		    (sg = session_group_contains(s)) != NULL) {
+			if ((sg == current && s != data->fs.s) ||
+			    (sg != current && s != TAILQ_FIRST(&sg->sessions)))
+				continue;
+		}
 		l = xreallocarray(l, n + 1, sizeof *l);
 		l[n++] = s;
 	}
@@ -805,6 +817,7 @@ window_tree_init(struct window_pane *wp, struct cmd_find_state *fs,
 		data->command = xstrdup(WINDOW_TREE_DEFAULT_COMMAND);
 	else
 		data->command = xstrdup(args->argv[0]);
+	data->squash_groups = !args_has(args, 'G');
 
 	data->data = mode_tree_start(wp, args, window_tree_build,
 	    window_tree_draw, window_tree_search, data, window_tree_sort_list,