Syon Park in London drew a record 15,000 people to its Enchanted Woodland event over nine nights. Head gardener Topher Martyn said word of mouth and repeat visits were the main reasons.
"I think it helps that we are low-key, friendly, reasonably priced and have lots of free parking," he added. "However, the secret of our success is that, although the lights are installed by a professional company for obvious reasons, we all do the event on top of our day jobs.
"There's no PR team feeding stories to the press, no budget for adverts on the Tube - just me and Emma, ably assisted by Glynis. Even our friendly local coffee shop sells tickets for us. I run things on the night but we have cleaners, managers, maintenance staff and gardeners all pulling together on the event and all giving up their weekends for it."
Money will go on restoring wrought-iron garden gates, repointing the floor of the Great Conservatory, starting work on the roof and addressing the levels of eutrophication in Capability Brown's Serpentine River.
At Royal Botanic Gardens, Kew, venue hire and events head Adam Farrar said of the garden's first Christmas lights trail: "Christmas at Kew has been a tremendous success. We welcomed more than 10 times the number of visitors we would normally expect to see during December.
"We hope our visitors went away inspired with a new view of Kew. Our beautiful winter landscape means that Kew has something to offer all year round and we are looking forward to building on the success of this first year to make Christmas at Kew a festive season must on the London calendar."