The garden product wholesaler, which employs 250 people is continuing to trade but Douglas-Davies said: "Going forward this is very concerning as I genuinely don't think alternative sources of product are in a position to instantly pick up the supply chain. I'm sure in the long term they will sort it out but our focus is on the next few weeks."
He thanked Solus staff past and present for their work supplying a "key part of my ranging decisions" over the years.
GCA chairman Will Armitage said: "I hope a long-term plan that brings this period of uncertainty to an end is found soon for the sake of the staff, suppliers and customers."
Solus had negotiations with Scotts about a takeover but they broke down and no other company has made an acceptable offer.
The 30+-year old company peaked at a £90m turnover and 300 staff but that fell to £29.3m in the six months to March 2014. Rob Hunt and Tony Barrell of PwC are joint administrators. They said Solus hopes to keep trading and to find a buyer.
Brands include Joseph Bentley tools and Chapelwood birdcare. Solus distributed Scotts, Sinclair and Bayer, who have all pulled out. Other brands such as Neudorff and Vitax remained with the company.
Decco and Stax have taken on some of the garden centre supply business.
Solus managing director Nick Davies left in 2013 after almost 30 years at the business to set up Crest Garden, after owner Simon Yealland appointed his son Ross in a senior role. Mark Pearson took over as chief executive in November 2013.
Solus sent out deliveries on 16 May and will review their position with key clients in the week beginning 19 May.