You can use a scrub brush and water in order to remove the stains after moving the pots. This will require a little effort and there is a high chance that your stain will be gone with this method.
Apply liquid dish soap
In case scrubbing is not effective, apply liquid dish soap or dampen the area and add dry detergent on the stained area. You need to leave the dish soap on the stain for few minutes. Then dip hard brush into a pot of hot water and apply on the stained area. Repeat the procedure if you fail to remove the stain in the first go. Remember to take caution when applying the hard brush so that you do not burn yourself. Also do not let vegetation and plants touch the soap.
Pour vinegar on the stained area and leave it there for 60 to 120 minutes. In case it dries out then add more vinegar. Then you need to scrub off the stain with the help from brush. Repeat the process until the stain disappears. Remember that vinegar kills plant so stop it from falling off the concrete.
Oxygenated bleach and hot water
You need to take one part of hot water and mix two parts of oxygenated bleach in a bucket. Pour the mixture over the stained area and leave it there for few minutes. After this take a brush dipped in hot water and wipe off the solution. Repeat the process if necessary for removing stubborn stains.