More than 100 industry guests heard environment minister Lord Henley acknowledge the importance of the industry, which contributes £9bn to UK GDP.
He said the coalition Government was committed to promoting "grow your own" schemes as well as launching a national tree-planting campaign next week and publishing a white paper on the environment in the new year.
"We are keen and we are convinced that this is what we must do to move forward," he told the gathering at the House of Commons.
Opening the reception, APPGHG chair Baroness Fookes outlined the group’s work including a recent first meeting for industry representatives with secretary of state Caroline Spelman.
After thanking all-party group officers for the "door to Westminster" it provides for horticulture, HW editor Kate Lowe highlighted deep concerns within the sector over the expected impact of cuts to local authority green space services.
"The green space professionals who HW speak to week in week out fear that it will be the very local low-profile pocket parks that typify green space in the most deprived areas that will be hardest hit by maintenance cuts," she said.
She added that the sector continued to need the group’s help "to ensure that during the passage of key planning changes, measures are included that encourage the provision of decent, usable green space that is vital to our lives".
Television gardener Toby Buckland echoed those concerns, saying: "These are tricky times but we have to look at our green spaces not only as the lungs of our cities, but as the heritage and the health of our towns.
"Society grows great when trees are planted and there are enough resources there to make sure that the trees grow."
Event sponsor Scotts Miracle-Gro Company managing director Martin Bready said the Government should support horticulture for its economic, health and environmental benefits. He said: "Focus on helping us with what we can do."
Attendees included Cheryl Gillan MP, Lord Taylor of Holbeach, Lord Palmer and Malcolm Wicks MP.