Landscaping is part of the first impression you are making which can sometimes be the most important. Buyers can be very visual. So if they see a yard in disarray it can definitely turn them off. Landscaping can be an easy and affordable way to aid in facilitating a sale.
It should be the landlord's responsibility to keep up appearances on the property. If they truly want to sell, they should take landscaping and maintaining it seriously. You could even show them all of these professional recommendations from people in the field who know from experience to help you out!