If it's dry now, it will take a little extra water to get down through the mulch. Water well before you mulch. But once you get a thick layer of mulch down, the soil will stay moist underneath a lot longer than before.

When deciding how much to water, there's no substitute for sticking a finger down through the mulch to check soil moisture level.

Happy mulching, and take care of your back!

I agree that making sure the area is deeply and thoroughly watered before the mulch is applied is very important.

Pop-up irrigation systems tend to be the least efficient at delivering water where it needs to go - the root zone - and are almost always programmed incorrectly. They should come on for an extended period of time less frequently (once or twice a week, depending on conditions) rather than for a few minutes on a daily basis. I can't tell you how long or how often - that depends on your soil and your climate - but you want to make sure to deliver enough water to percolate fully down through the root zone.

You will need to look at what is happening with the soil under your mulch to determine whether you need to change your sprinkler settings. Depth of the mulch can limit how much water reaches the soil, if insufficient amounts of water flow through the irrigation system or the system runs an insufficient amount of time to deliver the amount of water needed by the plants growing there.
Many people have seen the "rule" that lawns need 1 inch of water per week, which does not take into account the weather, with the hot, dry weather we have been having lawns will need more then that and that "rule" does not apply to the flower or vegetable garden.

Hi Kimmer:
"Many people have seen the "rule" that lawns need 1 inch of water per week, which does not take into account the weather, """

Regarding this....how does one know they have watered 1 inch? I just read an article that stated for a plant to have been watered 1 inch, the soil would be moist all around the drip line and down 8 inches! IS THAT RIGHT ? That seems like alot of water. Thanks for clarifying ....I'm in a servere drought here in C. IL.
S

Watering one inch is the amount of water applied per area. If you set out a bin and filled it with one inch of water, then the footprint of that bin would be watered one inch.

One cubic foot of water (12"x12"x12") is about 7.5 gallons. 7.5/12 = 0.625 gallons of water for each square foot in order to water one inch. So, if you have a 100 square foot garden, then it takes 62.5 gallons to water the entire area with one inch of water.

To illustrate with arbitrary values - in one case you spray the area for a while with 50 gallons from a sprinkler, much of the water evaporates into the air and never makes it beyond the mulch layer and the soil stays relatively dry. On the other hand, you could use drip emitters to supply one quart of water to each of twenty plants in the area underneath the mulch, 5 gallons of water is used and relatively little evaporates.

Of course how much water the garden actually needs or benefits from depends on many factors including mulch, soil type, plants, and weather.

Place several straight sided cans, tuna or cat food tins work really well, over the area being sprikled and water that area for a set period of time and then look at how much water is in those tins. If your watering system can deliver 1 inch in 1 hour then for each area being sprinkled you would need to run that sprinkler for an hour to deliver that 1 inch of water.
How often to water depends on what your plants, whether grass, flowers, or vegetables, tell you. When they show early signs of stress, due either to the heat or lack of soil moisture, it is time to water again. Plant leaves wilt, grass turns a bluish color.