diff --git a/jupyterhub/app.py b/jupyterhub/app.py
index db47ab69..1258f01f 100644
--- a/jupyterhub/app.py
+++ b/jupyterhub/app.py
@@ -298,9 +298,9 @@ class JupyterHub(Application):
         return classes
 
     load_groups = Dict(
-        Dict(),
+        Union([Dict(), List()]),
         help="""
-        Dict of `{'group': {'users':['usernames'], properties : {}}`  to load at startup.
+        Dict of `{'group': {'users':['usernames'], 'properties': {}}`  to load at startup.
 
         Example::
 
@@ -311,7 +311,8 @@ class JupyterHub(Application):
                 },
             }
 
-        This strictly *adds* groups, users and properties to groups.
+        This strictly *adds* groups and users to groups.
+        Properties, if defined, replace all existing properties.
 
         Loading one set of groups, then starting JupyterHub again with a different
         set will not remove users or groups from previous launches.
@@ -2079,12 +2080,18 @@ class JupyterHub(Application):
                 for username in contents['users']:
                     username = self.authenticator.normalize_username(username)
                     user = await self._get_or_create_user(username)
-                    self.log.debug(f"Adding user {username} to group {name}")
-                    group.users.append(user)
+                    if group not in user.groups:
+                        self.log.debug(f"Adding user {username} to  group {name}")
+                        group.users.append(user)
+
             if 'properties' in contents:
                 group_properties = contents['properties']
-                self.log.debug(f"Adding properties {group_properties} to group {name}")
-                group.properties = group_properties
+                if group.properties != group_properties:
+                    # add equality check to avoid no-op db transactions
+                    self.log.debug(
+                        f"Adding properties to group {name}: {group_properties}"
+                    )
+                    group.properties = group_properties
 
         db.commit()
 
diff --git a/jupyterhub/tests/test_app.py b/jupyterhub/tests/test_app.py
index 2a524e62..a26d191f 100644
--- a/jupyterhub/tests/test_app.py
+++ b/jupyterhub/tests/test_app.py
@@ -233,15 +233,16 @@ def test_cookie_secret_string_():
 
 
 async def test_load_groups(tmpdir, request):
+
     to_load = {
         'blue': {
             'users': ['cyclops', 'rogue', 'wolverine'],
-            'properties': {'setting1': 'one', 'setting2': 'two'},
         },
         'gold': {
             'users': ['storm', 'jean-grey', 'colossus'],
             'properties': {'setting3': 'three', 'setting4': 'four'},
         },
+        'deprecated_list': ['jubilee', 'magik'],
     }
     kwargs = {'load_groups': to_load}
     ssl_enabled = getattr(request.module, "ssl_enabled", False)
@@ -258,11 +259,17 @@ async def test_load_groups(tmpdir, request):
     blue = orm.Group.find(db, name='blue')
     assert blue is not None
     assert sorted(u.name for u in blue.users) == sorted(to_load['blue']['users'])
-    assert sorted(u for u in blue.properties) == sorted(to_load['blue']['properties'])
+    assert blue.properties == {}
     gold = orm.Group.find(db, name='gold')
     assert gold is not None
     assert sorted(u.name for u in gold.users) == sorted(to_load['gold']['users'])
-    assert sorted(u for u in gold.properties) == sorted(to_load['gold']['properties'])
+    assert gold.properties == to_load['gold']['properties']
+    deprecated_list = orm.Group.find(db, name='deprecated_list')
+    assert deprecated_list is not None
+    assert deprecated_list.properties == {}
+    assert sorted(u.name for u in deprecated_list.users) == sorted(
+        to_load['deprecated_list']
+    )
 
 
 async def test_resume_spawners(tmpdir, request):