You Garden is set to announce turnover for 2012 at £3m. McDermott said this year's sales are "broadly in line with expectations".
He said he was "prudent" about projections for 2013 and having a small team and low overheads helped the mail order plants business.
McDermott said clearing supplier surpluses also helped his business, which was started 18 months ago.
He added that a "lack of commitment" to orders by retailers had left many growers "high and dry" and that an "obsession" with cheap plants was damaging the industry.
He said the industry is selling plants too cheaply, and "silly deals" from Groupon and B&Q were taking value out of the supply chain.
He said the problem reflected the industry being unable to attract enough new entrants, and trade bodies needed to do more to promote the struggling industry.
McDermott added that a £30 bouquet of flowers was not an "armbreaker" but consumers quibbled over the price of a £30 tree or shrub.