The campaign aimed to plant 680,000 trees between 11am and 12 noon last Saturday (5 December). BBC television show Autumnwatch, the HTA, 1,000 garden centres, distributors and tree growers Alba and Cheviot linked to run the initiative.
The record for the most trees planted in one location in one hour was beaten at Gransha Park in Northern Ireland, with 26,422 trees. Simultaneous bids in Essex and Hertfordshire came in at 20,312 and 20,326 respectively.
Whether the world record was beaten for the most trees planted in multiple locations in one hour will be verified by the BBC next week.
HTA representative Gill Ormrod explained that the BBC was waiting for photos from planters to give evidence of plantings. These are due today (12 December). But she added: "Some garden centres had a few left."
London-based Adrian Hall Garden Centres representative Zoranka Wilson-Bligh said one of its three centres had some left, which will be given to schools.
Klondyke operations director David Yardley said across the business's 24 centres, many had a "favourable uptake". He added: "But given the weather on Saturday morning, people may have picked up trees but whether they planted them is another question."
A BBC representative commented: "All three teams vying for the single-location record broke the previous record by miles. Between them, they planted more than 67,000 trees.
"The other record news will take some time because we have to collate evidence from many thousands of planters and community groups who all got involved."