I discovered two of my favorite climbers there. Veichenblau is an unusually shaped, small, purple/blue once-bloomer that shows off its colors in large clusters. City of York is a simple, classic white rose but I can find it in any rose garden by its wonderful scent.
Although it’s in a nearby suburb, not Paris itself, you can take public transportation from central Paris. You can use the RATP trip planner to plan your trip to the nearby suburb of l’Hay les Roses, Bus Stop: Sous-Prefecture-Eglise. The bus stops right across from the entrance to the park.
A word about venturing out of central Paris; there will be fewer people who speak any English. Go armed with maps and visuals if you don’t speak any French. You can print out the informaton for the buses at the RATP site, for example. And I found it took me longer than the trip information said. On transfers, just about the time that I figured out which bus I should take it was pulling out and I had to wait for the next one. But it’s really fun to watch the bus drivers navigate those huge city buses through the tiny streets.