Recent years had seen the firm hit with unpaid debts of up to £1m as customers went under, said David O'nions.
O'nions responded on www.HorticultureWeek.co.uk to last week's news (HW, 18 September) explaining that, while the investment in Vapogro was a significant contributor, there were other issues that had hit the firm's success.
In addition to bad debt from growers, he added that a lack of support from banks had been "the final nail in the Avoncrop coffin".
According to O'nions, debtors included: Polehouse Nurseries, in Essex, which closed in 2007 with a loss of 150 jobs; PA Moerman, which folded in 2007 along with parent company Sutton Horticulture; and Starlight Growers, which went into liquidation in 2006.
Avoncrop director Mark Davies said: "They've all gone out of business. They are history."
One of the nurseries singled out as owing money to Avoncrop is Waterfield Nurseries in Goring Heath, Berkshire.
However, its current owner, David Wilson - who was hit by thieves who stole £3,000 of kit last month - told HW the problem had been with the previous owners.
"There are lots of people trying to collect money from the previous owners," he explained. "We kept the name because people know it, but we have had no dealings with Avoncrop."
Davies added that he expected to hear news of a sale of Avoncrop within the next couple of weeks.