HTML / CSS – li & ul overlapping issue

I’m using a theme which seems a tad broken.
I am trying to list categories with subs and within those are more subs.

ie: potato and celery are top level, with their subs and sub-subs.

potato

brown

washed

celery

green

long

The issue I’m having is, the top levels (potato and celery) are displayed one under the other, rather celery displayed after potatos last sub/sub-sub as shown above. This leads to all the subs of each, overlapping text.

ie:

potato
celerybrown

greenwashed

long

CSS

#sidebar ul li {
    height: 35px;
    line-height: 35px;
    border-bottom: 1px solid #f0f0f0;
}
    ul.ecart_categories { /* category list container */ }
    ul.ecart_categories li { /* category listing containers */ }
    ul.ecart_categories li a { /* category link default styles */ }
    ul.ecart_categories li a:hover { /* category link hover styles */ }
    ul.ecart_categories li span { /* categpry product count styles */ }
    ul.ecart_categories li.current { /* currently viewed category container */ }
    ul.ecart_categories li.current a { /* currently viewed category link style */ }
    ul.ecart_categories li.current a:hover { /* currently viewed category link hover style */ }
    ul.ecart_categories li ul.children { padding-left: 10px;/* sub-category list container */ }
    ul.ecart_categories li ul.children li { padding-left: 10px;/* sub-category listing container */ }
    ul.ecart_categories li ul.active { /* active sub-category container */ }

OUTPUT

<div class="one_fourth" id="sidebar">
    <li id="ecartcategorieswidget-3" class="widget-1 widget-first widget sbg_widget Shop widget_ecartcategorieswidget">
    <h2 class="widgettitle sbg_title">Categories</h2>
    <ul class="ecart_categories">
        <li><a href="http://www.myWPurl.com/?page_id=25&amp;ecart_category=30">Potato</a>
            <ul class="children">
                <li><a href="http://www.myWPurl.com/?page_id=25&amp;ecart_category=36">Brown</a>
                    <ul class="children">
                        <li><a href="http://www.myWPurl.com/?page_id=25&amp;ecart_category=40">Washed</a></li>
                    </ul>
                </li>
            </ul>
        </li>
        <li><a href="http://www.myWPurl.com/?page_id=25&amp;ecart_category=1">Celery</a>
            <ul class="children">
                <li><a href="http://www.myWPurl.com/?page_id=25&amp;ecart_category=2">Green</a>
                    <ul class="children">
                        <li><a href="http://www.myWPurl.com/page_id=25&amp;ecart_category=12">Long</a></li>
                    </ul>
                </li>
            </ul>
        </li>
    </ul>
    </li>
</div>