Call and ask!
I know that when my husband and I were renting while our house was being built, our landlord was more than happy to have my husband do small repairs around the apartment. We kept our receipts and he either reiumbursed us or took it off of our rent. Think about it... the things got fixed and all he had to pay for were materials! For example, we had a screen door with torn mesh.
We didn't paint, but my BIL just painted his rental house with the permission and input of the landlord. The owner preferred a certain brand, so they went with that. They also installed shelving in the bathroom closet to increase the storage. All of the above increased the value of the rental and they were reimburse...
As for the landscaping, I wouldn't suggest that you do that. The upkeep for the landlord should you move out is pretty substantial. What you consider to be low-maintenance may not be the same as the person who owns the home. Remember that while you are living there and want it to look nice, it's not "your house". Get some large planters and use potted plants. That way, if you move the changes are not permanent!