The days might still be scorching but fall it just around the corner! The cooler days and nights make fall and winter the perfect time to plant in Phoenix. In fact, the nighttime temperatures matter far more than people think. When we look at the weather we focus on the highs but when looking at your planting schedule consider all the weather variables, highs, lows, humdity and cloud cover. All of these factors contribute to the evapotranspiration rate. Basically, the amount of water lost over time to evaporation and transpiration. Haven’t heard of transpiration? It’s the rate at which plant loose water. I like to describe it as plant sweat. Evaporation, of course, is the water that turns into the gas in the sun/heat. A higher evapotranspiration rate places more stress on plants and they require extra water to keep their cells hydrated.
When we plant in the summer (and we do!) we have to ensure that the new plants with their small root systems are getting adequate water because they are loosing so much in the scorching heat. So we water them a lot. It is also much harder for the plants to recover from the initial plating shock. In the summer our plants are struggling to stay alive they don’t have extra energy for growing roots, leaves, or branches. Once they’ve been in for a few years, their root system in extensive and can help them withstand periods of stress but new plants are one stressful event away from death until they start to grow new roots and leaves. If you plant in the summer consider hiring an experienced landscaper or gardener who can explain your new plantings water needs and provide realistic expectations.
All that said, summer is almost over! In many places that’s a bad thing, not in Phoenix. Even though our high temetures are still above 100 our nights are falling into the 80’s. This means that our plants finally have the energy to grow. Those summer plantings your landscaper has been telling you look ‘fine’ for two months? They finally have the energy reserves to grow! Sure they are hot for a few hours in the middle of the day (aren’t we all) but during the night and the cool mornings they are busy making roots and leaves. They’ll be thriving by spring.
Those cooler nights will also help anything you plant now. They will recover from planting stress faster than your summer plantings and will have the energy needed to grow before the shorter days and colder temperatures of winter slow growth again. If you want a lush, beautiful garden quickly and with very little stress (to you are or the plants) fall is the time to plant. Start thinking about your landscape design in August or September so that you’re ready to take advantage of the cooler fall nights and get a beautiful garden.