Display post thumbnail in foreach loop

Question

I am trying to display a thumbnail in a foreach loop. The thumbnail is a new image size I have added called "plant-thumb". I have all the desired elements displaying properly except for the thumbnail. Here is my code:

      foreach ( $posts as $post ) {   

       echo '<a class="modalLink" href="plant-list-accordion'.$post->ID.'" >';
       echo get_the_post_thumbnail($thumbnail->ID, 'plant-thumb'); //Here is where I'm trying to output the bespoke thumbnail
       echo '</a>';

            $faq .= sprintf(('<div class="modal mfp-hide" id="plant-list-accordion'.$post->ID.'">%1$s<div>%2$s</div>'),
                $post->post_title,
                wpautop($post->post_content)
                 );
            $faq .= '</div>'; //Close the container
            }

        return $faq; //Return the HTML.
};

Answer 1

echo get_the_post_thumbnail($post->ID, 'plant-thumb');