Titchmarsh's charity helps fund gardens and green spaces in and around schools.
He told HW: "I started my schools gardening scheme in 2001 and it now includes 300 schools, but it's about to go up a gear and be run slightly differently. It will be announced next month. I'm talking to other people about joining with them. Yes, that may be the RHS." The RHS confirmed the link.
Titchmarsh and children from Beckwithshaw Community Primary School, in Harrogate, launched the educational centre, which is set to be visited by 10,000 children a year when it opens in early 2010.
The centre was originally intended by former Harlow Carr curator Matthew Wilson to diversify visitors to the garden to include more than just traditional RHS members.
RHS science and learning director Simon Thornton-Wood said: "The Learning Centre provides Harlow Carr with the outstanding facilities we need to help people enrich their knowledge and skills, whatever their level of gardening experience. Schools, families and individual gardeners will have access to first-class amenities within a building that reflects and exemplifies the environmental contribution that we believe people can make in their gardening."
The centre has space for seed and plant growing and gives access to the collections of the RHS Lindley Library.
Thornton-Wood added: "Children and young people in particular have fewer opportunities to gain familiarity and confidence with the natural environment. The skill and creativity of gardening with the RHS opens a new world of experience and enjoyment for many."
The RHS hopes the Harlow Carr Learning Centre will gain the highest rating (BREEAM*) used to recognise the UK's sustainable buildings.
The building's environmental credentials include: a zero-carbon rating; a wind turbine and ground source heat pump; construction from natural and recycled materials; a grey-water recycling system; passive solar heating and a sedum roof. It is designed by Andrew Yeats from architecture practice Eco Arc, based in Yorkshire.