Bacterial pest Xylella fastidiosa, which restricts water movement in plants, has caused devastation in mainland Europe, wiping out entire groves of ancient olive trees in Italy.
And it is only a matter of time before the disease is introduced to the UK on imported plants, the Royal Horticultural Society (RHS) said.
Garden favourites, including lavender, hebe, rosemary and flowering cherry are among the 350 types of plants at high risk of infection.
Gerard Clover, head of plant health at the Royal Horticultural Society, said: “Xylella is a game-changer for gardeners and the horticultural industry and it is vital that we understand its potential impact.
“Xylella is in a bit of a class of its own, because it kills plants, has insect vectors and such a broad host range.
“The RHS views the threat of Xylella as a pivotal point in the future of plant health in the UK and as such we have opted to increase our plant health provisions to counter the threat from the bacteria as well as the myriad of other pests and disease knocking at the garden gate.”
Mr Clover warned the disease could have a “fundamental” effect on gardens.
Originally from North and South America, Xylella is thought to have arrived in Europe on imported plants.
It can be transmitted by insects, making it easier to spread and infected plants may show no symptoms of the disease.
Experts urged people to buy plants that are grown in the UK and report potential cases of the disease to the Environment Department (Defra).
The European Commission approved greater protection against the spread of Xylella after Environment Secretary Michael Gove urged Brussels to bring in tougher measures including more checks on high-risk plants as they move between countries.
A spokesman for the Environment Department (Defra) said the threat that diseases such as Xylella posed was a “very real and growing concern”.
“That is why this year we have pressed hard at EU level for increased protections against Xylella, in order to prevent the devastating disease reaching our shores, and these were approved in October and came into force this month,” he said.
“When we leave the EU we will also have an opportunity to examine all our national biosecurity measures on plant imports to ensure they are as robust as possible to protect the UK against diseases like Xylella.”