We were lucky enough to go to the Phoenix Botanical Garden on National Public Gardens Day, which gave us free admission, although it was probably unusually crowded. When we took our tour of the Red Rocks State Park in Sedona, we learned a lot about cactus and desert plants. Unfortunately many of the plants they described as having colourful flowers were not in bloom at the time.
At the botanical garden finally we saw proof that beautiful lush plants and flowers actually could thrive in the desert. There was an entire trail devoted to desert wild flowers.
On the guided tour that we took, we learned about the Saguaro cactus which can grow up to 40 feet high, weigh over 6 tons and live for several hundred years and may not grow arms for the first 80+ years. The Saguaro is an endangered species so you need a permit to take any part of this cactus out of the desert (even a dead cactus is not allowed). We heard about a couple of guys who caught with a saguaro and were fined by the inch, resulting in a whopping $75,000 fine.
We were shown a sickly looking stick and were told that it was called the "Arizona Queen of the Night", which seemed like a lofty name for this stick. But apparently this plant blooms a beautiful flower for just one night, which then dies in the heat by the next day... blink and you'll miss it!
We also saw a tree aptly called the Palo Verde, that had green bark, tiny leaves and small yellow flowers. The leaves were too small to provide enough food for the entire plant, so photosynthesis also takes place in the bark to help out.