The UK's second biggest garden centre chain plans to launch the service early next year to serve the whole of the UK.
Dobbies chief executive Nicolas Marshall called the tie-up a "huge opportunity".
Garden centres currently do a "pathetically small" amount of business online compared to other retailers, Mr Marshall told the BBC.
About 40% of UK retail sales are online, but for gardening it is only a few percent, he said.
Garden centres make about £4bn in annual sales, estimated Mr Marshall, a former boss of the UK's biggest gardening retailer Wyevale.
"If we can get to 40% of £4bn, that's £1.6bn online, ten times our turnover - huge," he told BBC Radio 4's You and Yours programme.
Dobbies was sold by Tesco to a group of private investors, including retail specialists Midlothian Capital Partners, last year for £217m.
Dobbies' new chairman, Andrew Bracey, a co-founder of Midlothian Capital, has links to Ocado.
He was chief financial officer at the online specialist for three years until 2012.
Dobbies - which has its headquarters near Edinburgh - operates 34 garden centres in the UK.
Garden centre group Dobbies has struck a five-year deal with online grocer Ocado to expand its UK deliveries.