When my husband was alive we found that being outside and enjoying nature was very therapeutic (for both of us!)
The names of flowers didn't matter much to my husband but he loved the bright colours, whether walking in a park, around a garden centre or around the block to admire local front gardens - all the vibrant colours filled him with joy.
Early morning walks also provided an opportunity to see intricate cobwebs picked out by dew and in the winter 'Jack Frost' patterns on car windows intrigued him. After a rainfall it was interesting to see the number of worms that had surfaced from underground and snails that had climbed to higher points.
During the warmer months my husband developed a huge passion and interest in the importance of bees so we made sure to always seek out areas where they were busiest, as well as growing things to encourage them into our own garden. While we were bee watching there was ample time to spot butterflies, ladybirds and the less appealing (to me) spiders too. The important thing was to take time to stand or sit and observe - what would be a 10 minute walk for others might take us 30 minutes or more - but we saw and shared so much during that time.
Going to the local ponds or lakes to watch the local wildlife was equally calming - especially as the swans glided by so gracefully or as ducks lined up and led their boisterous ducklings, whether on land or water.
On a more practical level my husband enjoyed helping to fill up the bird feeders to encourage his feathered friends into the garden - we also found a winning hobby in growing potatoes and strawberries, something he could do with minimal interference from me - he loved to see how Mother Nature had everything under control to provide him with food to put on the table.
One lady with dementia that I used to walk with relished the autumn time in particular. The beautiful colours of leaves on the trees filled her with awe. Although in her 70s, once the leaves dropped she would put on her wellies and kick her way through huge piles of them, enjoying the sound of them so crisp underfoot. Her face would light up with this simple pleasure that took her back to her carefree childhood days. She also liked to pick up a conker or two to take home and admire. It was a very tactile experience for her.