The upstairs (head) tenant hasn’t mowed the lawn in months and garbage is piled everywhere. What can I do?

To start, you can talk with the upstairs tenant. Standard rental and lease agreements may specifically require a tenant to carry out certain basic activities, such as lawn mowing and weeding. Ask if they are, in fact, responsible for yard maintenance. A gentle reminder might just do the trick.  

If talking with your neighbour doesn’t help, you might consider writing a letter to the landlord. (You can use the Tenant Resource and Advisory Centre’s template letter to help you. Look for the one on loss of quiet enjoyment.) You can tell them how untidy or unsightly the rental property is, and how it's affecting you (including a few pictures can really drive the point home). 

Your landlord must investigate your complaint. If they’re aware of the problem and don’t take reasonable steps to protect your right to quiet enjoyment, you can take your landlord to dispute resolution through the Residential Tenancy Branch. If you prove your claim, you could get monetary compensation.