To make a navgation like that, I would recommend using xhtml and CSS.
The html should be along the lines of...
<div id="leftnav">
<h2>Trees & Shrubs</h2>
<ul>
<li><a href="#" title="Trees">Trees</a></li>
<li><a href="#" title="Shrubs">Shrubs</a></li>
</ul>
<h2>Perennials & Vines</h2>
<ul>
<li><a href="#" title="Perennials">Perennials</a></li>
<li><a href="#" title="Ground Covers">Ground Covers</a></li>
<li><a href="#" title="Grasses">Grasses</a></li>
<li><a href="#" title="Vines">Vines</a></li>
</ul>
</div>
Then within your CSS....
#leftnav {}
#leftnav ul {}
#leftnav li {}
#leftnav a {}
#leftnav a:hover {}
#leftnav a:visited {}
I hope this helps with the menu. Please let me know if you have any problems.
Michael.