diff --git a/public/javascripts/note_tree.js b/public/javascripts/note_tree.js
index 79866dfdf..16dfb94c7 100644
--- a/public/javascripts/note_tree.js
+++ b/public/javascripts/note_tree.js
@@ -6,6 +6,8 @@ const noteTree = (function() {
     let startNoteId = null;
     let treeLoadTime = null;
     let clipboardNoteId = null;
+    let notesMap = {};
+    let parentToNotes = {};
 
     function getTreeLoadTime() {
         return treeLoadTime;
@@ -19,8 +21,16 @@ const noteTree = (function() {
         clipboardNoteId = cbNoteId;
     }
 
-    function prepareNoteTree(notes) {
-        for (const note of notes) {
+    function prepareNoteTree() {
+        return prepareNoteTreeInner(parentToNotes['root']);
+    }
+
+    function prepareNoteTreeInner(noteIds) {
+        const noteList = [];
+
+        for (const noteId of noteIds) {
+            const note = notesMap[noteId];
+
             glob.allNoteIds.push(note.note_id);
 
             note.title = note.note_title;
@@ -28,19 +38,25 @@ const noteTree = (function() {
             if (note.is_protected) {
                 note.extraClasses = "protected";
             }
-            else {
-                if (note.is_clone) {
-                    note.title += " (clone)";
-                }
-            }
 
             note.key = note.note_id;
             note.expanded = note.is_expanded;
 
-            if (note.children && note.children.length > 0) {
-                prepareNoteTree(note.children);
+            if (parentToNotes[noteId] && parentToNotes[noteId].length > 0) {
+                note.folder = true;
+
+                if (note.expanded) {
+                    note.children = prepareNoteTreeInner(parentToNotes[noteId], notesMap, parentToNotes);
+                }
+                else {
+                    note.lazy = true;
+                }
             }
+
+            noteList.push(note);
         }
+
+        return noteList;
     }
 
     function setExpandedToServer(note_id, is_expanded) {
@@ -179,6 +195,16 @@ const noteTree = (function() {
                         }
                         break;
                 }
+            },
+            lazyLoad: function(event, data){
+                const node = data.node;
+
+                if (parentToNotes[node.key]) {
+                    data.result = prepareNoteTreeInner(parentToNotes[node.key]);
+                }
+                else {
+                    console.log("No children. This shouldn't happen.");
+                }
             }
         });
 
@@ -186,15 +212,16 @@ const noteTree = (function() {
     }
 
     async function reload() {
-        const treeResp = await loadTree();
+        const notesMap = await loadTree();
 
         // this will also reload the note content
-        await treeEl.fancytree('getTree').reload(treeResp.notes);
+        await treeEl.fancytree('getTree').reload(notesMap);
     }
 
     function loadTree() {
         return $.get(baseApiUrl + 'tree').then(resp => {
-            const notes = resp.notes;
+            notesMap = resp.notes_map;
+            parentToNotes = resp.parent_to_notes;
             startNoteId = resp.start_note_id;
             treeLoadTime = resp.tree_load_time;
 
@@ -202,16 +229,11 @@ const noteTree = (function() {
                 startNoteId = document.location.hash.substr(1); // strip initial #
             }
 
-            prepareNoteTree(notes);
-
-            return {
-                notes: notes,
-                startNoteId: startNoteId
-            };
+            return prepareNoteTree();
         });
     }
 
-    $(() => loadTree().then(resp => initFancyTree(resp.notes)));
+    $(() => loadTree().then(notesMap => initFancyTree(notesMap)));
 
     function collapseTree() {
         treeEl.fancytree("getRootNode").visit(node => {
diff --git a/public/javascripts/tree_utils.js b/public/javascripts/tree_utils.js
index db927deb4..b3993fdaa 100644
--- a/public/javascripts/tree_utils.js
+++ b/public/javascripts/tree_utils.js
@@ -43,11 +43,6 @@ const treeUtils = (function() {
             return "[unknown]";
         }
 
-        // why?
-        if (note.data.is_clone) {
-            return null;
-        }
-
         const path = [];
 
         while (note) {
diff --git a/routes/api/tree.js b/routes/api/tree.js
index 5129945fc..feb3d44aa 100644
--- a/routes/api/tree.js
+++ b/routes/api/tree.js
@@ -21,8 +21,8 @@ router.get('/', auth.checkApiAuth, async (req, res, next) => {
         + "where notes.is_deleted = 0 and notes_tree.is_deleted = 0 "
         + "order by note_pid, note_pos");
 
-    const root_notes = [];
-    const notes_map = {};
+    const parentToNotes = {};
+    const notesMap = {};
 
     const dataKey = protected_session.getDataKey(req);
 
@@ -31,30 +31,17 @@ router.get('/', auth.checkApiAuth, async (req, res, next) => {
             note.note_title = data_encryption.decryptCbcString(dataKey, data_encryption.noteTitleIv(note.note_id), note.note_title);
         }
 
-        note.children = [];
-
-        if (note.note_pid === "root") {
-            root_notes.push(note);
+        if (!parentToNotes[note.note_pid]) {
+            parentToNotes[note.note_pid] = [];
         }
 
-        notes_map[note.note_id] = note;
-    }
-
-    for (const note of notes) {
-        if (note.note_pid !== "root") {
-            const parent = notes_map[note.note_pid];
-
-            if (!parent) {
-                log.error("Parent " + note.note_pid + ' has not been found');
-                continue;
-            }
-            parent.children.push(note);
-            parent.folder = true;
-        }
+        notesMap[note.note_id] = note;
+        parentToNotes[note.note_pid].push(note.note_id);
     }
 
     res.send({
-        notes: root_notes,
+        notes_map: notesMap,
+        parent_to_notes: parentToNotes,
         start_note_id: await options.getOption('start_node'),
         tree_load_time: utils.nowTimestamp()
     });