In its response to the European Commission's consultation on the types of regulation needed for invasive plants, the HTA said the plant trade would suffer if an EU-wide list of plants that cannot be introduced in the wild was adopted.
The HTA claimed that an EU-wide blacklist could see plants added that are considered invasive in one EU country despite the fact that they may be harmless in the UK.
HTA policy manager Gary Scroby said this could be "damaging to the plant trade". In its response, it called for a "light-touch regulatory approach" supported by awareness-raising of the risks in the trade and to the public.
The association favours a blacklist over a "whitelist" of tested and approved plants but has warned that the EU will need to consider how it deals with "different risks in different countries".
In 2010, the HTA lobbied against the listing of many common garden plants in schedule 9 of the Wildlife & Countryside Act. Plants such as cotoneasters are not to be introduced in the wild but can still be sold and planted in other circumstances. The HTA argued that evidence was not sufficiently robust and it would create a "list of plants that landscape specifiers, without the background knowledge, would effectively ban". It had seen evidence of this and was raising the issue with Defra.
Johnsons of Whixley director Andrew Richardson said: "It's ridiculous - the Government is making it difficult for us to trade. A lot of the plants on the list might be invasive somewhere in the world but not in the UK."
Many the plants that could end up on an EU-wide list would be in the "top 20" of those sold in the UK, he said.