diff --git a/nvflare/app_opt/flower/applet.py b/nvflare/app_opt/flower/applet.py
index f34361bab5..63c63efc2d 100644
--- a/nvflare/app_opt/flower/applet.py
+++ b/nvflare/app_opt/flower/applet.py
@@ -26,9 +26,10 @@
 
 
 class FlowerClientApplet(CLIApplet):
-    def __init__(self):
+    def __init__(self, extra_env: dict = None):
         """Constructor of FlowerClientApplet, which extends CLIApplet."""
         CLIApplet.__init__(self)
+        self.extra_env = extra_env
 
     def get_command(self, ctx: dict) -> CommandDescriptor:
         """Implementation of the get_command method required by the super class CLIApplet.
@@ -62,7 +63,9 @@ def get_command(self, ctx: dict) -> CommandDescriptor:
         # this is necessary for client_api to be used with the flower client app for metrics logging
         # client_api expects config info from the "config" folder in the cwd!
         self.logger.info(f"starting flower client app: {cmd}")
-        return CommandDescriptor(cmd=cmd, cwd=app_dir, log_file_name="client_app_log.txt", stdout_msg_prefix="FLWR-CA")
+        return CommandDescriptor(
+            cmd=cmd, cwd=app_dir, env=self.extra_env, log_file_name="client_app_log.txt", stdout_msg_prefix="FLWR-CA"
+        )
 
 
 class FlowerServerApplet(Applet):
diff --git a/nvflare/app_opt/flower/executor.py b/nvflare/app_opt/flower/executor.py
index 2ee1d89e5a..88d8745b6f 100644
--- a/nvflare/app_opt/flower/executor.py
+++ b/nvflare/app_opt/flower/executor.py
@@ -15,6 +15,7 @@
 from nvflare.app_common.tie.executor import TieExecutor
 from nvflare.app_opt.flower.applet import FlowerClientApplet
 from nvflare.app_opt.flower.connectors.grpc_client_connector import GrpcClientConnector
+from nvflare.fuel.utils.validation_utils import check_object_type
 
 from .defs import Constant
 
@@ -27,18 +28,33 @@ def __init__(
         per_msg_timeout=10.0,
         tx_timeout=100.0,
         client_shutdown_timeout=5.0,
+        extra_env: dict = None,
     ):
+        """FlowerExecutor constructor
+
+        Args:
+            start_task_name: name of the "start" task
+            configure_task_name: name of the "config" task
+            per_msg_timeout: per-msg timeout for ReliableMessage
+            tx_timeout: transaction timeout for ReliableMessage
+            client_shutdown_timeout: how long to wait for graceful shutdown of the client
+            extra_env: extra env variables to be passed to client applet
+        """
         TieExecutor.__init__(
             self,
             start_task_name=start_task_name,
             configure_task_name=configure_task_name,
         )
 
+        if extra_env:
+            check_object_type("extra_env", extra_env, dict)
+
         self.int_server_grpc_options = None
         self.per_msg_timeout = per_msg_timeout
         self.tx_timeout = tx_timeout
         self.client_shutdown_timeout = client_shutdown_timeout
         self.num_rounds = None
+        self.extra_env = extra_env
 
     def get_connector(self, fl_ctx: FLContext):
         return GrpcClientConnector(
@@ -48,7 +64,7 @@ def get_connector(self, fl_ctx: FLContext):
         )
 
     def get_applet(self, fl_ctx: FLContext):
-        return FlowerClientApplet()
+        return FlowerClientApplet(extra_env=self.extra_env)
 
     def configure(self, config: dict, fl_ctx: FLContext):
         self.num_rounds = config.get(Constant.CONF_KEY_NUM_ROUNDS)
diff --git a/nvflare/app_opt/flower/flower_job.py b/nvflare/app_opt/flower/flower_job.py
index 0451bee409..97bcdbe899 100644
--- a/nvflare/app_opt/flower/flower_job.py
+++ b/nvflare/app_opt/flower/flower_job.py
@@ -47,7 +47,7 @@ def __init__(
         client_shutdown_timeout=5.0,
         stream_metrics=False,
         analytics_receiver=None,
-        client_api_type: str = "EX_PROCESS_API",
+        extra_env: dict = None,
     ):
         """
         Flower Job.
@@ -69,17 +69,13 @@ def __init__(
             client_shutdown_timeout (float, optional): Timeout for client shutdown. Defaults to 5.0 seconds.
             stream_metrics (bool, optional): Whether to stream metrics from Flower client to Flare
             analytics_receiver (AnalyticsReceiver, optional): the AnalyticsReceiver to use to process received metrics.
-            client_api_type (str, optional): Client API type, can choose from EX_PROCESS_API and IN_PROCESS_API
+            extra_env (dict, optional): optional extra env variables to be passed to Flower client
         """
         if not os.path.isdir(flower_content):
             raise ValueError(f"{flower_content} is not a valid directory")
 
         super().__init__(name=name, min_clients=min_clients, mandatory_clients=mandatory_clients)
 
-        if client_api_type not in ["EX_PROCESS_API", "IN_PROCESS_API"]:
-            raise ValueError("Invalid client api type.")
-        os.environ["CLIENT_API_TYPE"] = client_api_type
-
         controller = FlowerController(
             database=database,
             server_app_args=server_app_args,
@@ -96,6 +92,7 @@ def __init__(
             per_msg_timeout=per_msg_timeout,
             tx_timeout=tx_timeout,
             client_shutdown_timeout=client_shutdown_timeout,
+            extra_env=extra_env,
         )
         self.to_clients(executor)
         self.to_clients(obj=flower_content)