Tenant wants me to sod yard?

[Ashley V.]

I am about 6 months into a lease with a new set of tenants in my rental house. In the front yard there are several large oak trees and due to the shade the grass is very sparse. It has always been this way and the tenants viewed the house twice before committing to the lease. Per the lease the tenant is responsible for all yard maintenance. 

6 months into the lease they are starting to complain about the lack of grass in that area and have asked me to have it sodded. I have asked a lawn care company about sodding it just to get ideas and it will be very costly and they also cannot guarantee that the sod will last due to 1) large trees causing shade and sucking all of the moisture out of the ground and 2) poor soil in that area. They said it would be a lot of maintenance to keep it going.

Due to this I really don't want to invest $$ into the sod to only have it die later if the tenant does not maintain it property. It would be up to the tenant to properly water it and I just don't see her as being the type to maintain it. For instance, we just came out of a 4 month drought and she let several areas of groundcover die from not watering it and is also the type to complain about her water bill being high.

Should I just say no?  Or let her do it at her expense (which I doubt she will)?