The organisation has chosen trees as the plant of the month for November, promoting benefits such as adding height and structure to gardens, reducing carbon footprint and bringing shade and wildlife.
The campaign is also focussing on smaller trees for gardens with limited space, such as malus and prunus, betula and sorbus.
Nurseries involved in the campaign are aiming to get across the message that autumn is by far the best time to plant trees, allow roots time to esablish and therefore absorb more moisture when new growth emerges in the spring.
Frank P Matthews which is supporting the campaign said it has supplied 60,000 trees so far this autumn, and expects this to double before Christmas.
Plants for the campaign are chosen by British growers and retailers and Plant of the Month point of sale materials can be purchased through HTA partners Hortipak and Floramedia.