diff --git a/taxonomy_manager.module b/taxonomy_manager.module
index 99acdb4..119f1cf 100755
--- a/taxonomy_manager.module
+++ b/taxonomy_manager.module
@@ -1001,7 +1001,7 @@ function taxonomy_manager_tree_validate($form, &$form_state) {
   else if (is_numeric($form['#value'])) {
     $selected[$form['#value']] = $form['#value'];
   }
-
+  
   $vid = $form['#vid'];
   foreach ($selected as $tid) {
     if (!_taxonomy_manager_tree_term_valid($tid, $vid)) {
@@ -1061,6 +1061,150 @@ function _taxonomy_manager_term_get_lang($tid) {
 }
 
 /**
+ * Implements hook_field_widget_info().
+ *
+ * Allows the taxonomy_manager_tree form element to be used within Drupal 7 Field API.
+ */
+function taxonomy_manager_field_widget_info() {
+  return array(
+    'taxonomy_manager_tree' => array(
+      'label' => t('Taxonomy manager tree'),
+      'description' => t('Allows selection of terms via a dynamic tree of checkboxes, where parent
+        terms can be expanded and child terms loaded via AJAX.'),
+      'field types' => array('taxonomy_term_reference'),
+      'behaviors' => array(
+        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
+      ),
+    ),
+  );
+}
+
+/**
+ * Implements hook_field_widget_form().
+ *
+ * Describes a form widget built on the taxonomy_manager_tree type form element, usable with
+ * taxonomy term reference fields via Field API.
+ *
+ * @param $form
+ * @param $form_state
+ * @param $field
+ * @param $instance
+ * @param $langcode
+ * @param $items
+ * @param $delta
+ * @param $element
+ *
+ * @return array a form definition
+ */
+function taxonomy_manager_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
+  $default = array();
+  if (is_array($items) && !empty($items)) {
+    foreach($items as $item) {
+      $default[$item['tid']] = $item['tid'];
+    }
+  }
+  $element += array(
+    '#type' => 'taxonomy_manager_tree',
+    '#vid' => substr($field['settings']['allowed_values'][0]['vocabulary'], 11),
+    '#required' => FALSE,
+    '#tree_is_required' => $field['settings']['required'],
+    '#multiple' => ($field['cardinality'] > 1 || $field['cardinality'] == FIELD_CARDINALITY_UNLIMITED) ? 
+      TRUE: FALSE,
+    '#pager' => TRUE,
+    '#title' => $instance['label'],
+    '#description' => $instance['description'],
+    '#default_value' => $default,
+    '#terms_to_expand' => $default,
+  );
+  if (isset($element['#title']) && !empty($element['#title'])) {
+    $element['#prefix'] = '<strong>' . t($element['#title']) . '</strong><br />';
+    unset($element['#title']);
+  }
+  if (isset($element['#description']) && !empty($element['#description'])) {
+    $element['#suffix'] = '<div class="description">' . t($element['#description']) . '</div>';
+    unset($element['#description']);
+  }
+  
+  // Need to override the normal validation function, which won't be available in the $form array
+  // until after build.
+  $element['#after_build'][] = '_taxonomy_manager_field_api_widget_after_build';
+ 
+  return $element;
+}
+
+/**
+ * Sets the Field API widget to use the correct validation function, which will format selected
+ * items the way taxonomy term reference fields expect them.
+ *
+ * @param $element
+ * @param $form_state
+ */
+function _taxonomy_manager_field_api_widget_after_build(&$element, &$form_state) {
+  $element['#element_validate'] = array('taxonomy_manager_field_api_widget_validate');
+  return $element;
+}
+
+/**
+ * Validation handler for Field API widget. Gets selected terms and formats them the way they are
+ * expected to appear by taxonomy term reference fields. Also skips making sure selections are
+ * valid, since taxonomy term reference fields can perform their own (field-level) validation.
+ *
+ * @param $element
+ * @param $form_state
+ */
+function taxonomy_manager_field_api_widget_validate($element, &$form_state) {
+  $direct_parents = array();
+  $selected = array();
+  if ($element['#multiple']) {
+    $selected = _taxonomy_manager_tree_get_selected_terms($element['#value'], $direct_parents);
+  }
+  else if (is_numeric($element['#value'])) {
+    $selected[$element['#value']] = $element['#value'];
+  }
+  else {
+    $selected = _taxonomy_manager_tree_get_selected_terms($element['#value'], $direct_parents);
+    // Ensure there is only one selected term.
+    if (count($selected) > 1) {
+      $tid = key($selected);
+      $selected = array($tid => $tid);
+    }
+  }
+  // Reformat array of selected terms to the format expected by the taxonomy term reference field.
+  $items = array();
+  foreach($selected as $tid) {
+    $items[] = (array) taxonomy_term_load($tid);
+  }
+  // Sort items alphabetically
+  usort($items, '_taxonomy_manager_sort_selected_items');
+  // Send to $form_state
+  form_set_value($element, $items, $form_state);
+}
+
+/**
+ * Helper function to sort taxonomy term objects (cast as arrays) alphabetically.
+ */
+function _taxonomy_manager_sort_selected_items($term1, $term2) {
+  return strcasecmp($term1['name'], $term2['name']);
+}
+
+/**
+ * Implements hook_form_id_alter().
+ *
+ * Only allow single-value or unlimited-value fields when using the Taxonomy manager tree field widget.
+ *
+ * @param $form
+ * @param $form_state
+ */
+function taxonomy_manager_form_field_ui_field_edit_form_alter(&$form, &$form_state) {
+  if ($form['#instance']['widget']['type'] == 'taxonomy_manager_tree') {
+    $form['field']['cardinality']['#options'] = array(
+      FIELD_CARDINALITY_UNLIMITED => t('Unlimited'),
+      1 => 1,
+    );
+  }
+}
+
+/**
  * theme function for root element
  *
  * @param $element