The castle is a featured garden in the Visit England 'Year of the English Garden' campaign. It is set within 500 acres, including parkland, farms, woodland, a nine-hole golf course and formal gardens.
The Castle Island sits adjacent to the Great Water, created by Russell Page in the 20th century. The island will be the main focus for the gardening team in 2016, and presents "an exciting challenge", head gardener Andrew McCoryn said.
"The castle is at the heart and centre of the vast estate, but there is a lack of colour and planting surrounding the building, which looks out to a green croquet lawn.
"We are going to build a series of beds, which we are hoping to neutralise, whilst putting a planting scheme in place that is unique and unlike any of the other gardens on the estate. It won't be palms as seen in the Lady Baillie Mediterranean Garden or the colours of the Culpeper Garden. The castle garden will be more structured with a grand mix of colours, particularly silvers, whites and lime greens.
"We are going for an ethereal approach that will not steal the thunder away from the castle but will really support it. It is a big project and an exciting one."
McCoryn said among other plans for 2016 "we have already begun to develop the rockery, originally built as a 30ft high rockery in the 1930's, which is located next to the barbican mill area".
"We are going to restore it and rebuild the rockery to its 1978 design, by placing all the stones back in their original locations and replanting around them. This will create dry conditions leading down to the water's edge."
Designer Russell Page was also behind the Culpeper Garden, which takes its name partly from Sir Thomas Culpeper, who bought the Castle in 1632, and partly from Nicholas Culpeper, the 17th century herbalist.
Originally the site of the castle's kitchen garden, during Lady Baillie's ownership the Culpeper Garden became a cut flower garden. In 1980 Page transformed it into a large cottage garden, with low box hedges filled with roses, lupins, poppies and Lads' Love. The gardening team will continue to develop the Culpeper Garden this year, adding new plants to boost the variety of species and colour.
Last year the gardeners focused on the Lady Baillie Mediterranean Garden Terraces, designed by landscape architect Christopher Carter. The south-facing tropical terraced garden is McCoryn's top "must-visit" garden for 2016 visitors to the site.
He explained: "Last year, we introduced more palm trees and cacti and we invested a lot into our gardens across the estate, but primarily the Lady Baillie garden. This was definitely the most successful project of 2015, particularly all the work that has been done along the bottom terrace.
"Last summer we had added a whole other level to the terrace. We have a three hundred meter long boarder and within a year it is already planted up and looks mature, with a mixture of bananas and palm trees. The Lady Baillie garden is the castle's hidden gem and even on a busy day can be very quiet. In 2016, we hope to develop better access to the Lady Baillie Garden, so it can be enjoyed by more of our visitors."