Plant a tree on your birthday in your backyard garden or any random place and watch it growing as you are growing. Plant a tree on special occasions like your parents marriage anniversary & give it a name, preferably the year of anniversary. They will love it.
Don't gift a single rose, but gift a rose sapling to your beloved. Together you plant it somewhere that you can watch it growing. You will enjoy it.
Have a beautiful landscape of plants and grassland in and around your house. Even if it would be small place it will altogether change the beauty of your house and you will anyway have more Oxygen.
Have a roof-top or balcony garden if you are a city dweller and fall short of planting grounds. It is a fun to engage in caring them and nevertheless it would bring a continuous supply of scent, colorful flowers, and seasonal vegetables.
Have indoor pants like Indian Basil (Tulsi) or Aloe Vera in your living room. Enjoy the aesthetics they bring to your home . You know, the biggest advantage is that - they release Oxygen even during night by a process know as CAM (Crassulcean Acid Metabolism) unlike other plants who release Oxygen during day time by photosynthesis. Thanks to ancient Indian Vedic texts which suggests Basil to be planed in every households.