Ideal World Horticultural buyer James Carter said the split happened last week and there were "no hard feelings". He said new "serious budgets were hard to reach and he could not see that happening with one vendor".
T&M left QVC for an exclusive agreement with Ideal World in 2014 but other suppliers have since come in to the channel.
Carter has been looking for new grower suppliers and had six contact him after HW's recent article saying he was seeking them.
He said Ideal Shopping Direct had a £10m turnover in gardening, with 40-50 per cent of that, plants.
Adam Walcott and Angela Noghani are among the Ideal World gardening presenters.