You should deadhead whenever your geranium blooms begin to look brown or weak. ... Deadheading will encourage new, full blooms to grow in and replace any that look weak or less full. Work through your plant, doing this throughout its sections. You'll begin to see fresh new blooms in just a few days.

What happens if you don't Deadhead geraniums?

This pretty annual plant cleans itself by dropping the flower heads below. The plant will continue to flower all summer long with no extra work from you spent removing it's pretty blooms.

What to do with pelargoniums after flowering?

Most hardy geraniums need to be trimmed to keep them from overtaking other plants and to encourage new growth. Once the plant has finished blooming or you notice old growth, trim it back to within a few inches of ground level, or about an inch above the main stem.