Because three times a year they must strap on an abseil kit and drop 50 metres down the nearly sheer castle walls - to catch up on the weeding.
The work helps to conserve the granite stone walls of the 12th Century castle which need to be kept constantly clear.
The only way the gardeners can carry out their work is to abseil down the 50 metre high castle walls.
Located on an island 300 metres off the mainland, the medieval church and castle perch atop the island, cared for in partnership by the National Trust and the St Aubyn family who donated the castle to the Trust back in 1954.
Head gardener Lottie Allen said: "Abseiling has become an important skill to complete essential strimming and planting of the many nooks and crannies within the cliff face where plants grow in spite of the salty winter storms and the baking summer temperatures.
"We weed these areas three times a year not only to ensure the stonework remains intact and strong but also to allow the succulents planted within the walls, such as aloes and aeoniums, to thrive and flourish.
"It is a thrilling and unique experience to tend these gardens which are designed to be viewed from above. On a personal note, abseiling allows me to appreciate the spectacular views of our gardens across the seasons and in all weathers."
Early in 2015 the team will abseil again to plant a large shelf-like area above the East Terraces with succulents such as Agaves and Aeoniums, daisy-like Osteospermum and Agapanthus. They will also prune a largePuya – a genus of the pineapple family which has started to lean away from the rock face.
St Michael’s Mount is one of 41 castles cared for by the conservation charity and one of three places where ‘extreme weeding' takes place. The others are Bodiam Castle in East Sussex and Scotney Castle in Kent.