Speaking at Majestic Trees' 15th anniversary landscape industry biosecurity symposium, RHS council member Jon Wheatley said: "We have no policy yet" on species that are a threat but the RHS had discussed one last week.
High risk plants cited by Defra are imported coffee, lavender, oleander, olive, polygala, rosemary and almond plants.
Garden designer Andy Sturgeon said a potential Chelsea garden for 2018 he saw included an olive tree and that the selection committee "know what's going on". He said the "RHS is doing its best to put that message out".
Sturgeon added that clients put pressure on him but "a lot of nurseries have stopped supplying so we stopped buying olives". He added: "We have to take stock of what we're doing. There are plenty of other styles and directions we could go in. It's not a big deal to stop using all these plants. It's easy for us to stop buying compared to nurseries."
He said he would love to plant UK-grown plants when contractors have finished but clients often wanted projects done out of the UK season. Sturgeon added that he relied on plant traders and contractors to say where plants came from.
Good practice on commercial jobs was to only plant 5-10% of a single species to "futureproof" in case of plant disease, Sturgeon added.
Chief plant health officer Nicola Spence said in her keynote speech on "risk and responsibility sharing" that "possible actions" on Xylella could be as strong as "strengthening import and movement requirements for all multiplex hosts, or all hosts."
She said proposed changes at EU level were:
- harmonisation of diagnostic methods, revision of demarcation requirements from 10km to 5km,
- the option to lift demarcation after two years,
- stronger import plant passport and traceability requirements for high risk hosts
- stronger requirements for certain plants (coffee, lavender, oleander, olive, polygala, rosemary and probably almond) grown outdoors, under an EU derogation to have plant passports and be inspected/tested before movement.
These are due to be discussed this month and could come in by November.
Speaking about the £6bn industry, including £3.3bn crop, £0.9bn forestry and £1.8bn social and environmental value, Spence said UK plant health interceptions now numbered 1,400 a year. Italy accounted for just 200 of these, Holland fewer than 1000, with the most in the UK from Asia and Africa. She added: "We don't have good figures on intra-EU trade because it's an open market."
Spence said her top pest and disease concerns were currently Xylella, plane wilt, long horn beetles, pine processionary moth, emerald ash borer and birch bark borer.
She said Defra secretary of state Michael Gove was "passionate about doing as much as he can to protect the UK from Xylella" after Gove warned the EU he could ban Xylella host imports.
Spence added she was "very, very concerned" about Xylella, because it could be confused with other symptoms and was "quite difficult to detect" although the UK had good tests and should be encouraged the rest of Europe to copy them.
Spence, who thanked Horticulture Week for its Xylella coverage, said Xylella was now "impossible to eradicate from Italy".
She said "it is crazy moving high risk hosts unchecked".
Spence said any finding would be designated as an outbreak, which would mean a 10km plant movement ban zone, or an interception, which would be less severe and would mean "localised" action.
Garden writer Peter Seabrook said after opening the new visitor advice centre at the Hertfordshire tree nursery, that stopping Xylella was "up to us". Hundreds of thousands of lavender are imported annually was "madness" when they could be UK-grown under glass with LED lights in winter, he said. He compared Xylella to bird flu or foot and mouth for plants.
Johnsons of Whixley director Andrew Richardson said in June 2017, the nursery stopped buying from Italy. He said Crowders had supplied an imported ash dieback-infected tree to a Leicester hospital scheme in 2012 but that could easily have been Johnsons of Whixley and "we don't want to be the ones brining xyella into the country and have the responsibilyt and ramifications". He said it was "easy" to convince customers they were doing the right thing not selling them imported stock, and that the HTA Xylella code was too "minimalistic and should be a lot stronger".
Palmstead's Nick Coslett said only 20% of Palmstead's stock was traded and he had stopped importing from Italy and Spain. He questioned other EU countries' plant health regimes and said European nations are not going to protect the UK and "if that is the case we have to protect ourselves". Spence said all EU plant health services were audited every five years and Italy was being audited annually.
Spence said she was often asked "why not ban it?" but said World Trade Organisation and EU rules meant that was difficult "unless you feel under imminent threat". She said UK concern had sent "shockwaves" around the EU.
Provender's Richard McKenna said he was worried about parallel imports by garden designers, which cut out plant passports and UK nurseries. He called for a plant health ratings website to show nursery cleanliness, adding that any plant import ban would create a "black market".
Spence said within two years (by December 2019) new EU regulations would mean all plants for planting would need passports and "all plant traders will have to come into line with that", including internet and "man with van" traders. She said the UK would bring in the rules even when it has left the EU.
Boningale's Tim Edwards has pioneered an HTA plant health assurance system which Johnsons of Whixley and other nurseries are now piloting. Spence said the scheme was critically important. Edwards said nurseries were going to end up with "an awful lot of responsibility" with plant health and plant specifiers have also got responsibility and that means they need more training.
BALI's Wayne Grills said an industry system agreed by everybody would be ideal and that the message needed to be spread about the risks.
The Society of Garden Designers plan a plant health continous professional development stipulation vote this month.
Meanwhile, the HYA is planning an outdoor Chelsea Flower Show garden for 2018.
Nursery consultant John Adlam said Xylella could devastate UK plant production and sales and that the UK industry had suffered after chalara, sudden oak death and Asian longhorn beetle outbreaks: "I would say the UK growers are not over-reacting but are in fact taking a very sensible precautionary view, understanding full well the disaster that could occur if this disease is found in the UK."
Hayloft Plants' Derek Jarman said: "It's common sense. Don't import a problem." he said importing plants from from the host areas was bad for gardeners and growers.
He said those that had decided to stop importing from wider areas or whole genuses were making a "commercial decision that is right - no-one wants to bring in trouble".
But he said a campaign to raise public awareness, which he said was low, could be seen as a "negative" and lead gardeners to not buying plants: "It's up to the industry to take sensible precautions. People might be put off buying plants in general so its best to shut up and get on with it."
Buckingham Nurseries' Chris Day said the garden centre tends to use third party UK-based growers that import and don't import direct themselves, mainly because minimum order values caused by carriage costs are too high.
The nursery imports from Italy and Holland at the beginning of spring when stock is acclimatised to be brought on to the same level of the UK summer. But they do not import later in the season because of the risk of plants dying.
He said there was still demand for olives in all formats although supermarkets stocking olives had "diluted" sales in garden centres.
Day said he sources rosemary and lavender from UK growers when possible though some named varieties do come from Holland. He said Buckingham does not deal in large Italian-grown one litre stock.
He said more awareness is needed to get the message out to consumers about the potential dangers of Xylella, adding: "We're doing our bit being careful where we get our stock from. But a better awareness campaign in the consumer market might be good, especially in spring when people will be buying Italian and Spanish stock, which is more susceptible."
Palmstead Nurseries Nick Coslett has decided not to import high risk specimens and will now seek to increase production of plants such as rosemary and lavender, and find alternatives to specimens such as olives.
Coslett added: "We imported rosemary and lavender at those times of the year when our production was on the low side. We will increase our production to fill that sort of gap.
"We have to act responsibly as a grower, importer and supplier."
Palmstead is also starting to grow more phormium again.
He said he will stop importing any olives and have to hope designers understand when current quarantined stocks are sold they can't get any more in.
He suggested willowleaf pear, cornus, arbutus or pines as alternatives.
Coslett said biosecurity in some of the Mediterranean countries hit by Xylella is "tricky" and "we're not able to rely on these nation states' own plant health systems - we can't rely on them to protect the UK".
He said Defra don't want to "rock the Brexit boat" too much though believes Defra secretary of state Michael Gove wants more restrictions in place. Some continental growers say EU rules are too draconian and are driven by the French to protect their wine market.
There are no controls and no way of stopping Xylella migrating through southern Europe. The EC extended the 300-plant host list this month.
#A scientific conference on European research into Xylella fastidiosa is to be held in Palma de Mallorca, Spain, from 13-15 November 2017. The conference is being organised jointly by EFSA, the University of the Balearic Islands, the Euphresconetwork for phytosanitary research coordination and funding, the EU Horizon 2020 projects POnTE and XF-ACTORS, and the European Commission’s Directorate-Generalfor Research and Innovation (DG RTD).
The event will provide a platform for in-depth discussion on the results of research into X. fastidiosa and its vectors, in support of on-going efforts to control the European outbreaks. As well as speakers and participants from Europe, the conference will be attended by scientific experts from other parts of the world – such as Brazil and the United States – where X. fastidiosa has been present for many years.