Coroner Elizabeth Pygott summed up for an hour on the third day of the resumed inquest.
The jury had heard that the 31 year-old accounts manager, who was born in Wellington, was struck by a falling cedar tree branch. Her friend, fellow New Zealander Tessa Marshall said she witnessed a "thud" as a branch fell 22m on a "yucky day" of weather at the gardens.
Tree experts Dr David Lonsdale, appointed by the coroner, and Jeremy Barrell, for the family, had given accounts on whether summer branch drop caused the branch failure.
Barrell had said it was caused by summer branch drop and that if the tree had been pruned the accident would not have happened. He called Kew's tree risk assessment management system "a shambles" and "not fit for purpose".
Lonsdale said the system was "robust" and that summer branch drop was ill-defined - but that the cause was "akin" to summer branch drop.
Kew arboretum head Tony Kirkham had said "squally" weather of 50km/hour wind gusts and 5mm rain in the hour before the incident was the cause.
Kew horticulture head Richard Barley said: "The jury had found that there was no identifiable cause of branch failure from this tree which caused this accident. We of course continue to extend our greatest sympathy to the family and friends of Miss Wilson affected by this tragedy. However, we can reassure everybody that Kew places the utmost importance on the safety of its tree collection for all of our visitors and employees.
"And as noted by the independent expert in this case, there was nothing that could be foreseen, there was no action, that he felt could or should have been taken and that the trees were being managed in an entirely appropriate and responsible way."
Wilson's parents said in a statement that they wanted more research into summer branch drop as a scientific phenomenon.
Chris Wilson and Elizabeth Shelley said in a statement: "First we would like to thank the jury for the time and consideration that have given to their deliberations. Second, the loss of our darling daughter Erena shattered us as a family and our memory of her is particularly vivid today, as the circumstances around her death are brought to the fore. Our thoughts are not only with Erena, but our hearts go out to all the families that have lost loved ones in similar circumstances. Third, even though the jury was not able to determine the cause of the branch failure that killed Erena, our hope is that the circumstances of Erena's death will significantly raise public awareness of the deadliness of the summer branch drop and lead to urgently needed funding and research into this phenomenon. If one death could be prevented
and one family saved from having to go through this, then some good will have come from this tragedy."