The Wilko offer, which replaces a two-for-£4 offer, is valid until 14 May. Six packs are £2.50 sold separately.
Riggs said the offer is programmed and "no one is hacking prices to bits". He added that B&Q's "teabag technology" coir biodegradable pots at four for £10 are doing well because of their novelty and good weather.
He said if the plant looks good and the price is reasonable, customers will buy, with price not the foremost consideration. "People are not as price sensitive as we think."
But Tillington plant buyer Andy Bunker said: "There will be a price war among the multiples because they're fighting for market share." Tillington bedding is generally £3.49 for a six pack, with three for £10.
Bunker pointed out that non-garden centre bedding often comes in smaller cells and has been produced to meet a price point.
Delamore's Wayne Eady said: "I don't think there's a need for that type of promotion unless it is related to poor forecasting. Generally, bedding is selling well."
- Homebase will not copy B&Q's teabag technology. A representative said: "We continually trial new packaging but will only launch alternatives when we are happy that plant quality is not adversely impacted. This is not something we are trialling and we feel our current packaging offers optimum protection."