Urban Guerilla Gardening

Urban Guerilla Gardening

I am tired of looking at the weeds surrounding the maple trees out front of my building, so I am plotting to have the weeds removed, and replaced with something more pleasant to look at. The problem being, that it's a small shallow square of dirt in a sidewalk, that dogs feel free to use as a toilet. Two years ago I planted a fair amount of zinnias and coleus, which worked for awhile, but they were gradually killed off one by one over a month's time by inconsiderate people's antics, and incontinent dogs with bowel problems. I am asking the group what plants they think would be a good idea to plant in these 2 squares out front. Something that is hardy, or likes abuse. Something that will tolerate heat and sun, with periodic shady periods due to parked cars nearby. Perhaps something that grows densely enough that dogs will think twice about relieving themselves on. Pee is one thing, it's the other part of the equation that drives me nuts. I'll consider fencing options but being a street level affair, it can't be anything too fancy or too big, or anything I don't want to lose at some point to a drunken fool sitting down on it. Simply put, any suggestions and brainstorms would be appreciated. I'm in Zone 4b but then remember: I am thinking more about perennials.
Problem peas

Problem peas

De-lurking!

De-lurking!

Lena’s Apartment: Installment 1, the  Nursery

Lena’s Apartment: Installment 1, the Nursery

My room

My room

the only blemish

the only blemish

Holiday Room Cheer

Holiday Room Cheer