Marketing director Andrew Maxted said the promotion with Taylors Bulbs was the latest in a series "that have been enthusiastically received by NGGV stockists this year and have helped grow overall sales of the vouchers again in the first eight months of the year".
He added: "All NGGV stockists were invited to support the 2010 promotion at the beginning of the season on the understanding that participation in individual promotions was at the discretion of each member business."
Maxted continued: "Digging for Daffs forms part of a public relations and media campaign to persuade garden owners to plant in the autumn for next spring."
One garden centre owner said: "We have received the latest HTA promotion to increase sales of vouchers but the offer is awful. We have three rather small bulbs. Is this really going to make people buy more vouchers? I think not."
Burcot Garden Centre owner Neil Gow said: "As a retailer, are three bulblets going to make someone by gift vouchers? I doubt it."