diff --git a/wagtail/wagtailadmin/widgets.py b/wagtail/wagtailadmin/widgets.py
index 4e65201f2..69282378d 100644
--- a/wagtail/wagtailadmin/widgets.py
+++ b/wagtail/wagtailadmin/widgets.py
@@ -15,6 +15,17 @@ from wagtail.wagtailcore.models import Page
 from taggit.forms import TagWidget
 
 
+class AdminAutoHeightTextInput(WidgetWithScript, widgets.Textarea):
+    def __init__(self, attrs=None):
+        # Use slightly better defaults than HTML's 20x2 box
+        default_attrs = {'rows': '1'}
+        if attrs:
+            default_attrs.update(attrs)
+        super(AdminAutoHeightTextInput, self).__init__(default_attrs)
+
+    def render_js_init(self, id_, name, value):
+        return '$("#{0}").autosize();'.format(json.dumps(id_))
+
 class AdminDateInput(WidgetWithScript, widgets.DateInput):
     def render_js_init(self, id_, name, value):
         return 'initDateChooser({0});'.format(json.dumps(id_))
diff --git a/wagtail/wagtailcore/blocks/field_block.py b/wagtail/wagtailcore/blocks/field_block.py
index c6dd7b166..76c2dd9f4 100644
--- a/wagtail/wagtailcore/blocks/field_block.py
+++ b/wagtail/wagtailcore/blocks/field_block.py
@@ -68,13 +68,18 @@ class CharBlock(FieldBlock):
 
 
 class TextBlock(FieldBlock):
-    def __init__(self, required=True, help_text=None, max_length=None, min_length=None, **kwargs):
-        self.field = forms.CharField(
-            widget=forms.Textarea(),
-            required=required, help_text=help_text,
-            max_length=max_length, min_length=min_length)
+    def __init__(self, required=True, help_text=None, rows=1, max_length=None, min_length=None, **kwargs):
+        self.field_options = {'required': required, 'help_text': help_text, 'max_length': max_length, 'min_length': min_length}
+        self.rows = rows
         super(TextBlock, self).__init__(**kwargs)
 
+    @cached_property
+    def field(self):
+        from wagtail.wagtailadmin.widgets import AdminAutoHeightTextInput
+        field_kwargs = {'widget': AdminAutoHeightTextInput(attrs={'rows':self.rows})}
+        field_kwargs.update(self.field_options)
+        return forms.CharField(**field_kwargs)
+
     def get_searchable_content(self, value):
         return [force_text(value)]