The St Albans visitor attraction, built by butterfly expert Clive Farrell on land sold to him by the Royal National Rose Society, will close for the winter on 4 October after a four-month run.
Future Gardens featured 12 avant garde gardens by designers including Andy Sturgeon and Peter Thomas. Organisers blamed high ticket prices, poor signposting and the weather for the poor attendance. Projected ticket revenue was £2.5m but organisers introduced two-for-one tickets within weeks of the attraction opening in June.
The 12 new gardens planned for 2010 will now not be built.
But the £27m project's senior commercial director Angela Harkness denied that the future of phase two — the Eden Project-style 100m-long Butterfly World butterfly dome due for a 2011 opening — was in jeopardy.
She said: "Future Gardens obviously has not worked to the levels projected. Now it is a case of getting on with the dome.
"We are in the middle of a lot of negotiations. We have two major investors looking at investing in the project to take it to the next level.
"We will probably be making an announcement about investment in the next few weeks.
"It is a brilliant project. Phase one has not gone as well as it should have done but phase two was not reliant on phase one.
"Once the dome is up and running, we will continue to run the competition gardens."
TJM Associates was in charge of delivering the 12 conceptual gardens in the project's opening phase, Future Gardens. But partner Therese Lang said that it was still owed tens of thousands of pounds, adding that poor promotion was one of the problems: "If you walked down the high street and asked people, they would never have heard of it."
Farrell said: "It has been a struggle. I'm not going to pretend it has been anything else. Projections proved over-optimistic and entrance charges over-optimistic."