RHS director general Sue Biggs and HTA chief executive Carol Paris invited industry figures to the event which was held at Parliament, and attended by MPs and peers.
While Eustice could make no promises as most of the 'asks' fall outside his department, he reiterated his support for the industry.
He said he was "reassured by the commitments of the industry" and that he wanted to change perceptions of horticulture as a poor career.
Eustice said he would do "everything he could" to help horticulture, an industry where he used to work, including for ornamental grower Bransfords, and as a strawberry grower in Cornwall.
He said: "I welcome the work that you’ve all done to put together this action plan. It does include asks of government, but what I’m reassured by, as well, is that in [the plan] there are lots of commitments from industry to help themselves and to actually move forward certain projects.
"I want to thank you all for all of the hard work that you’ve done to put into this action plan I think it’s very important. This is a crucial, vital industry about which I am passionate about and if there’s anything I can do to help you implement this plan and take it forward I’m more than willing to do all I can."
Lords minister Lord Gardiner, who oversees plant health, was also in attendance, as was Lord Taylor of Holbeach, Baroness Fookes and Baroness Royall.
Sunday trading remains a focus with the HTA pledging to campaign for an exemption for garden centres even if a relaunched and unaltered Bill to get an extension through Parliament fails in February, as revealed in HW yesterday, now that SNP MPs are set to be cut out of voting the Bill down. This could make the industry £75m a year, said Paris.
She added: "The future is bright however, and I believe we are entering a golden age for the horticulture industry. By taking horticulture into the realms of health, environmental and societal benefits – more than just looking pretty – we are developing new markets and skills as well as tackling some of the biggest national and global problems we face. We have never seen lasting collaboration on this scale before, and it is definitely starting to bear fruit."
Eustice said BIS was "looking into" Sunday trading. He added that there was a "mismatch" between fragmented, small producers and large procurers that he wanted to address.
HS2 was mentioned by Eustice but the industry is feeling frustration that its discussions to give it lead-in time to grow trees for the scheme are being hindered by delays in the project's procurement plan.
Import substitution was another topic, which Eustice said could cut European imports of pests and diseases, but UK plant buyers say growers have cut production in the UK, meaning they often have to look overseas for plants.
He added on imports: "Too much comes from Holland. The more we can expand...our own industry the more we can reduce plant disease".
The plan calls for UK plants procurement only for UK public bodies.
Eustice supported an idea for a garden expo. The garden industry has been in discussion with the Town & Country Planning Association to link such a project with a New Town build.
Biggs said health and wellbeing was a focus as much as commerce for the Round Table.
The RHS said it would hold a health seminar "natural health service" event at Hampton Court Flower Show in July.
Biggs said for the first time horticulture was "unified", thanks to the Round Table, which she chairs.
She said solving the horticulture skills shortage, highlighted in RHS document Horticulture Matters three years ago, was part of the new campaign.
Biggs added: "It is great to see UK horticulture unified and focussed and working together to take on the challenges that have for far too long held this sector back. Horticulture has a vital part to play in the future of this country – not only for the fiscal health of this nation with its £10.4bn contribution to the UK economy. But also for the health and well-being of our country, of our people, our plants and our environment."
AHDB's Martin Emmett runs the education and employment side of the Action Plan, while Paris runs the commercial and promotion side and RHS science head Alastair Griffiths runs the science and R&D side.
Paris said "generation rent" meant that 20- and 30-somethings were the first "non-gardening generation".
She said "increasing competitiveness is a theme throughout the plan".
Also at the event, the AHDB launched the delayed Horticultural Innovation Partnership strategy, rewritten to fit in with the round table plan.
AHDB took over HIP last year.
The Round Table has 12 'asks' relate to careers, curriculum, tourism, Sunday trading, expo, supply chain, financial incentives, R&D, sustainable resourcing, plant health, human health and green infrastructure.
Baroness Royall introduced the event. RHS ambassador George Hassall, aged 10, spoke of how learning gardening at school had helped his education.
At an HTA chief executives event before the Parliament meeting, lobbyist Mark Glover spoke about the pros and cons of Brexit-leaving the EU.