Food and feed may be imported, and cut GM carnations in unusual colours have been brought in from Colombia to Europe for 15 years, but EU regulations ban the growing of the carnations within the union.
Thompson & Morgan managing director Paul Hansord said he "would consider" selling plants produced with biotechnology in the UK. He added: "The cost of UK registration would not be too much of a problem if we could get permission from the breeders."
Suttons Seeds horticultural manager Tom Sharples said: "Our policy is never say never. At the moment it's no GM, but if we saw a tremendous benefit for the home gardener, like blight-free tomatoes, it's something we'd look at. We'd need to be convinced it's a safe product, and development costs are so huge - for instance, the extra costs of the GM geranium per plant; it's difficult putting that cost into ornamentals."
Spanish-bred GM pollen-free geraniums from Instituto de Biologia Molecular y Celular de Plantas emerged this year but are not available for sale in the EU.
Dr Julian Little, chair of the Agricultural Biotechnology Council, said: "A GM plant not destined as either food or feed still has to get a full EU clearance before being imported - such clearances remain difficult due to some delays around scientific assessment and member-state voting that plagues food and feed dossiers.
"You would think that politicians would consider a flower colour trait as being much less important than something that reduces allergies. The reality is that regulators will take a lot longer to muse over the science and the politicians will be hypersensitive to the fact the regulators have taken a long time; so don't hold your breath."
Greengene International owner Professor Geoff Dixon said a "test case" is needed to bring GM ornamentals into the UK. He added: "I can't see any justification not to. There's no wild population that's going to be affected and it's arguable that the geraniums would survive in the wild anyway. If amateur gardeners want them, do it."
Both the Soil Association and Garden Organic charities are strongly opposed to GM in food, but have no view on GM in ornamentals. Plants for Europe executive director Graham Spencer said: "I've always believed that consumer resistance to GM would be too great. Also there's an issue of licensing."