My container garden has anywhere from 25 to 30 pots each year. One would think that by now, I would have invested in a drip irrigation system to save myself the trouble of thoroughly watering each container every day (and sometimes twice a day) in the summer. But one would be wrong because I water the old fashioned way, with a hose and a sprayer. I had a nice surprise waiting for me one morning this week because my husband bought me a new, really cool water wand. It has about 10 settings and the force of the water stream can be adjusted by a little lever at the base. A similar one can be found on Amazon or probably in just about any hardware store. Very handy.
One reason I have not installed drip irrigation is that watering by hand each morning affords me the opportunity to inspect each plant to see how it's faring, if there are any pests bothering it or if it needs any extra attention. I would probably not take the time to scrutinize that closely if I had a system that automatically did the watering for me.
Of course, manually watering is a fair amount of extra work and in the dog days of summer, if I'm not out there before about 8:30 a.m., I can be drenched in sweat in less than five minutes. If that's how I feel, I can only imagine how my plants are suffering. My point is, in the heat, plants, like people, need lots and lots of water. Here are some things to remember:
The smaller the pot, the more frequently it needs to be watered.
Avoid overhead watering, you need to get the water down into the soil so it can really get to the roots.
Try to elevate all containers using plant stands or pot feet so that there is good air circulation underneath.
Soak the pot until you see water dripping out from the holes you are supposed to have at the bottom. (see post: Let's Talk About Pots)
It's always best to water early in the morning so that any water that might get on the leaves has a chance to evaporate. This minimizes the risk of fungal diseases.
Just because it rains, doesn't mean you're in the clear. Check the pots anyway because the rain may not have been sufficient to get through the foliage and soak way down into the soil.
Be extra vigilant about watering when plants are first put in soil because that's what they need to establish strong root systems.
Bookshelf: Container Gardening Books