The Beauty of Gas Stations
One really good way to know if a plant is hardy, is to see if it's growing in one of the many landscapes in and around gas stations. Why? beause you can be certain that no one is watering them. Here is an example. 
In this garden by the Petro Canada at Meadowvale and Sheppard, there is an ideal selection of plants that you can neglect. Purple Sandcherry is definitely a good pick, but they do get quite spindly as they get older. I always plant a small to medium sized shrub in front of them to hide the their "trunks".When kept small, I really like the contrast in colours between Golden Mock Orange and Purple Sandcherry. Cut Leaf Stephanendra, Annabelle Hydrangeas, Viburnums and some Spireas are often used by the neglectful gardener. Of course there is the ever unfailing until it does, humble Juniper (as seen in the foreground in this photograph) A few years ago there was a terrible problem with Scale in the city of Toronto, but barring that Euonymus, is a favorite among home owners who want a plant to last years in a long slow drawn out death.
A few perennials can survive being negelected, like Hollyhocks. On Laird Ave at their bloom time (which happens from around nowish and for the next few weeks) go check them out! There is nothing else in this garden but Holly Hocks and it is amazing. It is an automotive business, or maybe a restaurant supply on Laird, on the east side just south of Eglinton.(added just one day later-today I drove by on my way to the Home Depoo and guess what? someone ripped out all of the Hollyhocks and put in tons of Tomato plants!)
Peonies, and tree Peonies? I have seen more than one stand at the egde of somewhere, with no one looking after it, and year after year they came back faithfully. The best testiment to the hardyness of a tree Peony, is this gorgeous yellow specimen in my brother's garden. I can promise you without a shadow of doubt in my mind, that my brother in the 3 years that he has been living here, has NEVER watered this Tree Peony.
Daylillies are amazingly
hardy, especially the variety that is bright orange, and are blooming right now called Hemerocallis fulva "Europa".
On Bathurst St. just north of St. Clair at the Shell station is a great hedge of Dwarf Koren Lilac, that seems to be doing really well, and of course the scent is incredible.
Another good way to see if a plant is hardy is to see if it is growing wild at the side of the road. A few weeks ago the Service Berry trees were in bloom and they were magnificent. Along the road that boundaries the Toronto Zoo is a huge stand of Service Berries, 
pictured here. The fruits are ready now and they are so soft, nutty and refreshing.
What is in your garden that seems to be thriving on neglect?
