The amendment to the Sunday Trading Act 1994 would give local authorities in England and Wales the power to allow garden centres to open for extended hours on selected Sundays.
Most garden centres fall into the "large shop" restriction, preventing them from opening for longer than six continuous hours between 11am and 5pm on a Sunday.
The proposed change would enable councils to allow additional opening hours of up to eight hours between 9am and 7pm. The local authority would not be bound by a set number of days and could restrict the number of Sundays the centre could open to just spring and summer, or to a single Sunday to allow for Easter Sunday trading.
HTA director general David Gwyther said the bill came out of last year's failure of a larger bill to change shop hours. It was the first time such a bill had been laid by the garden industry, he said.
As a draft bill laid in the Lords, it would still have to be adopted in the House of Commons. Gwyther said: "We're not promising results overnight but if the bill gets a good hearing there's every chance it will go to the Commons.
"Nothing has happened on Sunday trading since 1995 when a bill went through imposing the current restrictions. This has caused considerable problems for centres trying to explain why they are closed when other shops aren't."