Visitors gathered in the rain at the Maybridge Keystone Centre, in Raleigh Way for the opening of the new Breathing Spaces garden.
The new facility will mainly provide gardening opportunities for residents with dementia but will be available to all.
Tarring councillor Hazel Thorpe, one of the organisers, said: “It is incredibly important because it doesn’t matter what age you are, we all lose our memory from time to time and gardening can be very therapeutic, using all the senses.
“We had quite a few people turn up from different groups and it just showed how important it is by the amount of people turning out in the rain.”
Breathing Spaces is a community interest company, run by Lisa Leach and Claire Hunt.
The garden was partly funded by a grant from West Sussex Social Enterprise Network, while trees were donated to the centre by the Woodland Trust.
Guests on the opening day included actress Amanda Waring, who actively campaigns for people with dementia.
Miss Leach said: “The opening went really well. We had a grant from WSSEN that we would build three gardens within the town in a year, for horticultural therapy.
“There is another garden at the Sidney Walter Centre and another at Linfield House, a Guild Care home.
“We work within care homes and the community.”
Therapeutic gardening sessions will be available on Monday afternoons each week.
The garden is part of the centre’s long-term plan to introduce a vegetable patch for all age groups to enjoy.
For more information about the sessions, contact Miss Leach on 07827 924151 or Ms Hunt on 07508 178590.