New HTA research has found that garden centres could take £12.1 million on the day alone, extrapolated from there being 2,200 garden retail outlets in the UK, each with the potential to earn £5,500 in sales per centre.
The association is also campaigning to extend the Sunday trading hours beyond the current six hours allowed by law.
If the campaign is successful the potential profit of Easter Sunday opening and extended Sunday trading hours could be "huge", say the HTA.
HTA horticulture head Raoul Curtis-Machin said: "For members its an 'archaic law'. It’s a daft law given technology today, where you can sit outside a garden centre and buy whatever you want but you can’t go inside."
He said the HTA had sympathy with some of the arguments of family Sunday but "Easter is one of the busiest times of the year and you can’t really get that back".
But he added that the big argument is "once a garden centre loses trade time in early spring they can’t make that up again throughout the rest of the year.
"Other outlets that must also close sell other products which will sell other times of the year so they are less affected by closure as sales of other items bring in income to counteract the loss at Easter."
He said the HTA had started a new lobbying campaign and had been heard by "gobsmacked" MPs.
See HW 18 April for more.