Rupert Precious, who worked at T&M for 15 years, has set up Mont Rose as part of a 50/50 partnership with Guernsey Clematis.
Precious said plants offered will be mostly from the UK and the Channel islands, with Raymond Evison's Clematis featuring prominently.
"The company takes in all my experience of supplying plants through reader offers and promotions in the client marketplace.
"I helped to set up T&M's client base from zero to what it is today and hope to replicate that success.
"There is a little bit of growth in the reader-offer market, although it is mostly competition moving around from supplier to supplier. Young plants are where the volume is, particularly in the spring."