The brass has been varnished to be water resistant, but remember to wipe away any sap residue from the brass surface. If you leave the water in the vase for a long period without replacing it with fresh water, sap residue/particles might penetrate the varnish and the brass may become discoloured.
Some types of plant fertilizers can have the same effect on the metal part. Wash the insert with water and non-abrasive washing detergent. It may be hard to remove sap that has penetrated the varnish – it is therefore important to make sure to immediately wipe away any plant residue. The brass insert will get patinated with time.
