I did it to prevent water evaporation it doesn't work? thank you

I guess it might if there was a large enough expanse of surface area exposed to the air and sunlight :-) But that is seldom the case with any of my container plantings........typically, the spread of the plant shields the surface from excess sunlight. And it rarely gets hot enough in my climate for heat to contribute much to evaporation. If that seems to be the case, I just bump up my watering schedule!

OTOH in my windy coastal area of SE Virginia, I find mulch is essential to conserve moisture and keep the soil temperature down. Our climate is 8A but this little strip of coast is almost as hot as Charleston SC.

My smallest pots have garden phlox and heuchera; the largest are roses.

Everything I grow in ground or in containers has mulch. Just think of a forest and how lush everything is with its natural layer of mulch. it protects from the cold, helps retain moisture in the soil and adds nutrients to the soil. You will find various opinions on the topic but you need to do what works for you. My plants, fruit trees (20 in containers, 7 in ground) are lush and healthy. I have my trees in half wine barrels. All my berries(mulberry, strawberry, raspberry,blueberry plants) I have over 30 varieties in containers have mulch and are doing fantastic the last 3-5 years.

It is a false assumption to make ANY sort of comparison about a forest mulch and a container plant - two entirely different sets of growing conditions with virtually nothing in common other than they can both support plant life!!

Mulch on the top of a container does nothing to protect from temperatures, either hot or cold. The biggest concern about a container overheating or cold exposure is from the sides and the bottom....and no amount of a topdressing mulch is going to help with that. And fast drainage is typically one of the primary concerns when growing anything in a container, so I do not want to cover with anything that will impede or slow drainage......or help to retain more moisture. That should be the function of the media....not any sort of mulch.

Mulching any inground plantings is highly recommended for any number of reasons. But those same reasons just do not exist with container gardening!

While I agree with GG on the soil temp issue, I respectfully disagree on the moisture retention issue. In a windy conditions, mulch does help retain moisture by reducing evaporation and prevents the wicking of moisture from the soil.

Unless a very wide container with a lot of bare soil mix showing, the effect of evaporation from the soil surface is minimal. And a mulch does nothing to protect or otherwise shield the deeper soil, which will retain moisture depending on its composition and whether or not the container is permeable (terra cotta versus plastic or glazed ceramic).

Can you cite any research on that, or is that from your observation/opinion?

My position is from my observance/opinion.

In a sheltered location in high humidity levels in the PNW, evaporation may be negligible, but in windy location at low humidity, I think there would be a noticeable effect. Wind and low humidity take its toll on not only the soil, but the plants as well, causing them to require more water from the soil. Every drop counts.

Perhaps the increased uptake of water by the plant gives the illusion of the soil drying at a more rapid rate. I'll have to check the physics on this one....But I'm still mulching my plants! (sticking thumbs in ears, waving fingers furiously) TTHHBTBTBTBTBT!!!

LOL!

Despite what you may have heard, we do NOT have high humidity here in the PNW :-) Even now, in the middle of our rainy season, relative humidity is only 84% and in summer hovers somewhere around 10-15%.

And where this comes from is basic soil science. Yes, it was intended for inground soils but is just as applicable to containers although the effect is greatly reduced. In general when the leaf canopy is 60% or more of the exposed surface, surface soil evaporation is negligible.

But if you like, mulch to your heart's content. It may not make any difference to the soils but if it makes you happy...........:-)