HTA Garden Industry Monitor data estimated that consumer spend on conifers increased from £14m in the year ending October 2007 to £14.5m in the year ending October 2008.
In the garden centre channel where National Conifer Week is focused, the HTA estimated that the increase in consumer spend on conifers in the past 12 months was nine per cent.
The Association of British Conifer Growers (ABCG) and the HTA's Plant For Life run the campaign.
HTA promotions manager Jennifer Thwaites said: "We're increasing the campaign this year by making conifers October's plant of the month. Sometimes conifers have been forgotten in garden centres but we want to promote them as useful and stylish for winter."
She added that there had been no decision on continuing the campaign for 2010 but that the ABCG is keen, as are garden centres.
Golden Acres Nursery owner and ABCG chairman Roger War added: "Conifers are a wonderful way of adding colour and shape to your outdoor space. While being practical they are also visually stunning and can transform a garden. Many conifers change colour throughout the year, so you can achieve fabulous splashes of orange, blue or purple in autumn or winter when other plants are dormant."
Thuja (arborvitae): ornamental and hedges
Juniperus (juniper): different types can be used in borders, rockeries and containers
Taxus (yew): ornamental, hedges and topiary
Picea (spruce): different types can be used in borders, rockeries and as specimen plants
Pinus (pine): used as dwarf ground cover
Cryptomeria (Japanese cedar): specimens and informal hedge
Chamaecyparis (cypress): specimens, screening and hedges
Abies (silver firs): specimens