Analysts say Halloween is an important indicator for Christmas sales.
HTA marketing director Andrew Maxted said: "As Pippa Goodman from the Future Foundation flagged up at the HTA Garden Futures conference last week, quality time with family and friends is a very important driver for consumers."
He said Halloween combined with half-term and good weather had meant good footfall for garden centres because Halloween and Bonfire Night were "opportunities for families to get together and celebrate". Maxted said this meant Christmas prospects are good for centres offering more authenticity than many high-street outlets.
He said trees, holly, food from food halls and quality gifts, especially for grow-your-own fans, meant "prospects are strong for garden centres this Christmas".
School half-term provides an opportunity to run unusual events for children. One of the oddest is from Squire's, which hosted bubble displays on 29 October.
Piles of pumpkins will be making the "perfect Halloween haven" for youngsters at Webbs Garden Centre at Wychbold. More than 2,000 pumpkins from Broomfields Farm Shop at Holt are being prepared for delivery to Webbs, for special hands-on pumpkin workshops.
North One Garden Centre in London has a pumpkin power event.