diff --git a/CMakeLists.txt b/CMakeLists.txt
index b31c85e..4c138f6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -128,7 +128,7 @@ include( "${CMAKE_CURRENT_LIST_DIR}/tools/cmake/DownloadDependency.cmake" )
 # These are replaced by tools/cmake/update_dependencies.sh to the hashes that are currently checked out.
 # Thus, do not replace the hashes manually!
 SET( CLI11_COMMIT_HASH "13becaddb657eacd090537719a669d66d393b8b2" ) #CLI11_COMMIT_HASH#
-SET( genesis_COMMIT_HASH "1bafc7b9b0ebfe07f366c818c524c3991490aa29" ) #genesis_COMMIT_HASH#
+SET( genesis_COMMIT_HASH "d0d574ed8026b2ca557a3b8458102cc142ca2558" ) #genesis_COMMIT_HASH#
 SET( sparsepp_COMMIT_HASH "6bfe3b4bdb364993e612d6bb729d680cf4c77649" ) #sparsepp_COMMIT_HASH#
 
 # Call the github download function, which takes four arguments:
diff --git a/doc/md/clean-tree.md b/doc/md/clean-tree.md
new file mode 100644
index 0000000..e551742
--- /dev/null
+++ b/doc/md/clean-tree.md
@@ -0,0 +1,15 @@
+## Description
+
+The command cleans a tree in Newick format (and some of its extensions) by removing parts that might lead some downstream parsers to fail.
+
+The Newick file format for phylogenetic trees in its original standard only supports node names (taxa names) and branch lengths. Over the years, many ad-hoc and custom extensions have been suggested and used in practice, to compensate for missing flexibility of the format.
+This however lead to many downstream parsers not being able to work with all those dialects of the format, see
+
+> A Critical Review on the Use of Support Values in Tree Viewers and Bioinformatics Toolkits.<br />
+> Czech L, Huerta-Cepas J, Stamatakis A.<br />
+> Molecular Biology and Evolution, 17(4), 2017.<br />
+> https://doi.org/10.1093/molbev/msx055
+
+for some of the issues that might arise.
+
+This command can be used to clean some of those difficult extensions/annotations, by simply removing them. It is meant as a cleaning tool for other software packages that cannot read a given Newick tree. When all options are activated, all types of extra data (that we know of) are removed, leading to a tree with just node names at the terminal (leaf) nodes, and branch lengths. Note that branch lengths might slightly change even if nothing is removed, due to numerical rounding.
diff --git a/libs/genesis b/libs/genesis
index 1bafc7b..d0d574e 160000
--- a/libs/genesis
+++ b/libs/genesis
@@ -1 +1 @@
-Subproject commit 1bafc7b9b0ebfe07f366c818c524c3991490aa29
+Subproject commit d0d574ed8026b2ca557a3b8458102cc142ca2558
diff --git a/src/commands/prepare.hpp b/src/commands/prepare.hpp
index c182570..a614cb3 100644
--- a/src/commands/prepare.hpp
+++ b/src/commands/prepare.hpp
@@ -3,7 +3,7 @@
 
 /*
     gappa - Genesis Applications for Phylogenetic Placement Analysis
-    Copyright (C) 2017-2021 Lucas Czech
+    Copyright (C) 2017-2022 Lucas Czech
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -27,6 +27,7 @@
 #include "CLI/CLI.hpp"
 
 #include "commands/prepare/chunkify.hpp"
+#include "commands/prepare/clean_tree.hpp"
 #include "commands/prepare/extract.hpp"
 #include "commands/prepare/phat.hpp"
 #include "commands/prepare/taxonomy_tree.hpp"
@@ -54,6 +55,7 @@ inline void setup_prepare( CLI::App& app )
 
     // Add module subcommands.
     setup_chunkify( *sub );
+    setup_clean_tree( *sub );
     setup_extract( *sub );
     setup_phat( *sub );
     setup_taxonomy_tree( *sub );
diff --git a/src/commands/prepare/clean_tree.cpp b/src/commands/prepare/clean_tree.cpp
new file mode 100644
index 0000000..ee359b7
--- /dev/null
+++ b/src/commands/prepare/clean_tree.cpp
@@ -0,0 +1,259 @@
+/*
+    gappa - Genesis Applications for Phylogenetic Placement Analysis
+    Copyright (C) 2017-2022 Lucas Czech
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+    Contact:
+    Lucas Czech <lczech@carnegiescience.edu>
+    Department of Plant Biology, Carnegie Institution For Science
+    260 Panama Street, Stanford, CA 94305, USA
+*/
+
+#include "commands/prepare/clean_tree.hpp"
+
+#include "options/global.hpp"
+#include "tools/cli_setup.hpp"
+
+#include "CLI/CLI.hpp"
+
+#include "genesis/tree/formats/newick/simple_reader.hpp"
+#include "genesis/tree/formats/newick/simple_tree.hpp"
+#include "genesis/tree/formats/newick/simple_writer.hpp"
+#include "genesis/tree/function/functions.hpp"
+
+#include "genesis/utils/core/fs.hpp"
+
+#include <cassert>
+#include <string>
+#include <stdexcept>
+
+// =================================================================================================
+//      Setup
+// =================================================================================================
+
+void setup_clean_tree( CLI::App& app )
+{
+    // Create the options and subcommand objects.
+    auto opt = std::make_shared<CleanTreeOptions>();
+    auto sub = app.add_subcommand(
+        "clean-tree",
+        "Clean a tree in Newick format by removing parts that other parsers have difficulties with."
+    );
+
+    // -----------------------------------------------------------
+    //     Input Data
+    // -----------------------------------------------------------
+
+    // Tree file
+    auto tree_file_opt = sub->add_option(
+        "--tree-file",
+        opt->tree_file,
+        "Tree file in Newick format."
+    );
+    tree_file_opt->check( CLI::ExistingFile );
+    tree_file_opt->group( "Input" );
+    tree_file_opt->required();
+
+    // -----------------------------------------------------------
+    //     Settings
+    // -----------------------------------------------------------
+
+    // remove inner labels
+    sub->add_flag(
+        "--remove-inner-labels",
+        opt->remove_inner_labels,
+        "Some Newick trees contain inner node labels, which can confuse some parsers. "
+        "This option removes them."
+    )->group( "Settings" );
+
+    // replace invalid chars
+    sub->add_flag(
+        "--replace-invalid-chars",
+        opt->replace_invalid_chars,
+        "Replace invalid characters in node labels (` ,:;\"()[]`) by underscores. "
+        "The Newick format requires node labels to be wrapped in double quotation marks "
+        "if they contain these characters, but many parsers cannot handle this. "
+        "For such cases, replacing the characters can help."
+    )->group( "Settings" );
+
+    // remove comments and nhx
+    sub->add_flag(
+        "--remove-comments-and-nhx",
+        opt->remove_comments_and_nhx,
+        "The Newick format allows for comments in square brackets `[]`, "
+        "which are also often (mis-)used for ad-hoc and more established extensions such as the "
+        "New Hampshire eXtended (NHX) format `[&&NHX:key=value:...]`. "
+        "Many parsers cannot handle this; this option removes such annotations."
+    )->group( "Settings" );
+
+    // remove extra numbers
+    sub->add_flag(
+        "--remove-extra-numbers",
+        opt->remove_extra_numbers,
+        "The Rich/Rice Newick format extension allows to annotate bootstrap values and probabilities "
+        "per branch, by adding additional `:[bootstrap]:[prob]` fields after the branch length. "
+        "Many parsers cannot handle this; this option removes such annotations."
+    )->group( "Settings" );
+
+    // remove jplace tags
+    sub->add_flag(
+        "--remove-jplace-tags",
+        opt->remove_jplace_tags,
+        "The Jplace file format for phylogenetic placements also uses a custom Newick extension, "
+        "by introducing curly brackets to annotate edge numbers in the tree `{1}`. "
+        "We are not aware of any other Newick extension that uses this style, "
+        "but still, with this option, all annotations in curly brackets is removed."
+    )->group( "Settings" );
+
+    // -----------------------------------------------------------
+    //     Output Options
+    // -----------------------------------------------------------
+
+    opt->file_output.add_default_output_opts_to_app( sub );
+
+    // -----------------------------------------------------------
+    //     Callback
+    // -----------------------------------------------------------
+
+    // Set the run function as callback to be called when this subcommand is issued.
+    // Hand over the options by copy, so that their shared ptr stays alive in the lambda.
+    sub->callback( gappa_cli_callback(
+        sub,
+        {},
+        [ opt ]() {
+            run_clean_tree( *opt );
+        }
+    ));
+}
+
+// =================================================================================================
+//      Run
+// =================================================================================================
+
+void run_clean_tree( CleanTreeOptions const& options )
+{
+    using namespace ::genesis;
+    using namespace ::genesis::tree;
+    using namespace ::genesis::utils;
+
+    // Check if the output file name already exists. If so, fail early.
+    options.file_output.check_output_files_nonexistence( "clean-tree", "newick" );
+
+    // If clean is given, read it.
+    LOG_MSG1 << "Reading input tree.";
+    auto tree = SimpleNewickTreeNewickReader().read( from_file( options.tree_file ));
+    LOG_MSG1 << "Tree contains " << leaf_node_count( tree ) << " taxa (terminal branches).";
+
+    // We want to warn the user if no cleaning option was provided.
+    bool ran_one = false;
+
+    // Remove inner labels
+    if( options.remove_inner_labels ) {
+        size_t cnt = 0;
+        for( auto& node : tree.nodes() ) {
+            auto& data = node.data<CommonNodeData>();
+            if( is_inner( node ) && ! data.name.empty() ) {
+                data.name = "";
+                ++cnt;
+            }
+        }
+        LOG_MSG1 << "Removed " << cnt << " inner node labels.";
+        ran_one = true;
+    }
+
+    // Replace invalid chars
+    if( options.replace_invalid_chars ) {
+        auto is_valid_name_char = [&]( char c ){
+            return   ::isprint(c)
+            && ! ::isspace(c)
+            && c != ':'
+            && c != ';'
+            && c != '('
+            && c != ')'
+            && c != '['
+            && c != ']'
+            && c != ','
+            && c != '"'
+            ;
+        };
+        size_t cnt = 0;
+        for( auto& node : tree.nodes() ) {
+            auto& name = node.data<CommonNodeData>().name;
+            bool valid_name = true;
+            for( size_t i = 0; i < name.size(); ++i ) {
+                if( ! is_valid_name_char( name[i] ) ) {
+                    valid_name = false;
+                    name[i] = '_';
+                }
+            }
+            if( !valid_name ) {
+                ++cnt;
+            }
+        }
+        LOG_MSG1 << "Replaced invalid characters in " << cnt << " node labels.";
+        ran_one = true;
+    }
+
+    // Remove comments and nhx
+    if( options.remove_comments_and_nhx ) {
+        size_t cnt = 0;
+        for( auto& node : tree.nodes() ) {
+            auto& data = node.data<SimpleNewickNodeData>();
+            if( data.comments.size() > 0 ) {
+                ++cnt;
+            }
+            data.comments.clear();
+        }
+        LOG_MSG1 << "Removed comments (such as NHX information) from " << cnt << " nodes.";
+        ran_one = true;
+    }
+
+    // Remove extra numbers
+    if( options.remove_extra_numbers ) {
+        size_t cnt = 0;
+        for( auto& edge : tree.edges() ) {
+            auto& data = edge.data<SimpleNewickEdgeData>();
+            if( data.values.size() > 0 ) {
+                ++cnt;
+            }
+            data.values.clear();
+        }
+        LOG_MSG1 << "Removed extra branch numbers on " << cnt << " branches.";
+        ran_one = true;
+    }
+
+    // Remove jplace tags
+    if( options.remove_jplace_tags ) {
+        size_t cnt = 0;
+        for( auto& edge : tree.edges() ) {
+            auto& data = edge.data<SimpleNewickEdgeData>();
+            if( data.tags.size() > 0 ) {
+                ++cnt;
+            }
+            data.tags.clear();
+        }
+        LOG_MSG1 << "Removed (jplace) tags on " << cnt << " branches.";
+        ran_one = true;
+    }
+
+    if( ! ran_one ) {
+        LOG_WARN << "No cleaning option was provided. Tree will be written as-is.";
+    }
+
+    // Create a newick tree from it.
+    LOG_MSG1 << "Writing output tree.";
+    auto nw = SimpleNewickTreeNewickWriter();
+    nw.write( tree, options.file_output.get_output_target( "clean-tree", "newick" ));
+}
diff --git a/src/commands/prepare/clean_tree.hpp b/src/commands/prepare/clean_tree.hpp
new file mode 100644
index 0000000..c6298c6
--- /dev/null
+++ b/src/commands/prepare/clean_tree.hpp
@@ -0,0 +1,65 @@
+#ifndef GAPPA_COMMANDS_PREPARE_CLEAN_TREE_H_
+#define GAPPA_COMMANDS_PREPARE_CLEAN_TREE_H_
+
+/*
+    gappa - Genesis Applications for Phylogenetic Placement Analysis
+    Copyright (C) 2017-2022 Lucas Czech
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+    Contact:
+    Lucas Czech <lczech@carnegiescience.edu>
+    Department of Plant Biology, Carnegie Institution For Science
+    260 Panama Street, Stanford, CA 94305, USA
+*/
+
+#include "CLI/CLI.hpp"
+
+#include "options/file_input.hpp"
+#include "options/file_output.hpp"
+#include "options/tree_output.hpp"
+
+#include <string>
+#include <vector>
+
+// =================================================================================================
+//      Options
+// =================================================================================================
+
+class CleanTreeOptions
+{
+public:
+
+    // Input data.
+    std::string tree_file;
+
+    // Settings.
+    bool remove_inner_labels     = false;
+    bool replace_invalid_chars   = false;
+    bool remove_comments_and_nhx = false;
+    bool remove_extra_numbers    = false;
+    bool remove_jplace_tags      = false;
+
+    // Output options.
+    FileOutputOptions file_output;
+};
+
+// =================================================================================================
+//      Functions
+// =================================================================================================
+
+void setup_clean_tree( CLI::App& app );
+void run_clean_tree( CleanTreeOptions const& options );
+
+#endif // include guard