3.5.2.1 atoms.form-controls.textarea.textarea-autogrow Textarea Autogrow

Toggle example guides Toggle HTML markup

If you want the textarea to autogrow while typing you need to add classes form-control--autogrow to the element as well. Also you need to remove the rows attribute.

Example
Markup: 02-atoms/form-controls/form-textarea-autogrow.twig
<textarea class="form-control form-control--autogrow" placeholder="Textarea with autogrow behavior"></textarea>
Source: 02-atoms/form-controls/_textarea.scss, line 17