But while on their travels it was said they met a gruesome end when they were targeted and kidnapped and beaten to death then put in their sleeping bags and thrown into a river infested with predators.
Their badly decomposed bodies had been eaten by river creatures when they were pulled out the water by fisherman days later but were unrecognisable as the missing couple and were deposited at mortuaries.
It was only months later when police could find no trace of them that they ordered all unidentified or unclaimed bodies in morgues to be DNA tested that they were identified.
The full-scale hunt for the couple who had vanished while collecting seeds had already resulted in four arrests - three of them who have been charged with their murder, kidnap, robbery and theft of the married couple.
Muslim convert Sayefundeen Aslam Del Vecchio, 39, and his wife Bibi Fatima Patel, 28, and their lodger at the time Mussa Ahmad Jackson, 35, all deny kidnap, murder, robbery and theft at Durban High Court.
The fourth suspect was found to have bought cell phones belonging to the Saunders and was not involved in the kidnap and killing and in return for vital evidence was given a suspended sentence.
The tragic couple were keen adventurers who set up a successful business in Cape Town selling seeds they found in remote areas to customers around the world and the court was told of their last journey.
They left their home in Cape Town in their Toyota Land Cruiser on February 5, 2018, to keep a rendezvous in the Drakensberg Mountains in Kwa-Zulu Natal 900 miles away with a BBC TV documentary film crew.
The internationally renowned botanists were interviewed by TV presenter Nick Bailey for an episode of Gardeners World as they searched the Drakensberg Mountain region for rare Gladioli flower seeds.
A selfie taken by Mr Bailey and posted on his Twitter account and a photo taken by producer Robin Matthews during filming were believed to be the last snaps taken of them alive.
After filming, expert horticulturist Rod and microbiologist wife Rachel who had been married over 30 years, parted ways with the TV presenter and headed off to camp at a dam by a remote forest.
They were last in contact with an employee at their workplace Silverhill Seeds which they ran from their home in Cape Town on February, 8, just three days after they had set off to meet the BBC.
Dr Saunders and her husband Rod said they were heading for the Ngoye Forest Reserve 90 miles north of Durban but were never heard from again and on February 10 the alarm was raised.
The court was told:"Around February 10 the investigating officer received information that Rodney Saunders and his wife Dr Rachel Saunders from Cape Town had been kidnapped in the Kwa-Zulu Natal region.
"It was established on February 13 that the defendants were drawing money from various ATM’s which amounted to theft of R734,000 (£37,000) and there was the robbery of their Land Cruiser and of camping equipment.
"It is alleged that between February 10 and 15 at the Ngoye Forest the accused did unlawfully and intentionally kill Rachel Saunders and between the same dates did unlawfully and intentionally kill Rodney Sanders" it was said.
On February 15, 2018, Sayefundeen Aslam Del Vecchio, 39, and his wife Bibi Fatima Patel, 28, were both arrested at their home in Endlovini which is just 30 miles from the Ngoye forest where the Saunders vanished.
It came after the Hawks which is an organised police crime fighting unit found a link between the cell phones belonging to Mr and Mrs Saunders and the cell phones of the suspects and they applied for a search warrant.
It was said that a number of items which had been bought on Dr Saunders bank card were recovered including receipts in the handbag of Bibi Patel which corresponded with the date and time of the use of Dr Saunders bank card.
The court heard:"On March 23 the third accused Mussa Ahmad Jackson was arrested and he made a statement to the effect he was woken by Patel at their home on February 10 and told to meet Del Vecchio on the road.
"Del Vecchio in the Land Cruiser and Patel and Jackson followed to the Tugela River Bridge where they helped him remove sleeping bags from the back of the Toyota and they threw them with human bodies inside into the river".
The victim’s Land Cruiser was recovered on February 19 with a large amount of blood in the cargo area which was later confirmed to be blood that belonged to one of the victims Dr Rachel Saunders, the court heard.
Rachel’s body had been recovered from the crocodile infested River Tugela on February 14 and Rod’s on February 17 by local fisherman but both bodies were not initially linked to the missing persons inquiry.
Later DNA checks in morgues finally showed a badly decomposed body in one mortuary came back on April 25 identifiying the male body as Rod and the other DNA check result which was received on June 6 identified Rachel.
It is believed both died from being beaten to death with a blunt instrument after being kidnapped and robbed and were then dropped off the bridge into the river for crocodiles to devour their bodies.
The indictment states that when the phones of all three were analysed their communications had WhatsApp messages that led to fears the group were members of terrorist group ISIS.
One message on February 9, 2018, discussed how they must "kill the kuffar (non believer) and abduct their alias, to destroy infrastructure and to put fear in the heart of the kuffar".
On February 10 a message from Del Vecchio to his wife and their then lodger said there was an elderly couple in the forest and that it is a good "hunt" and he has the "target".
Del Vecchio in a message to an unknown person allegedly sent "when the brothers in kinya go out and do this work it is very important the body of the victims is never found.
"It remains a missing person case" said the message. When Rod and Rachel first met he was a nursery manager at the world-famous Kirstenbosch Botanical Gardens in Cape Town and Rachel was a leading microbiologist at a nearby university.
Rachel was a keen collector of indigenous seeds and travelled to all corners of South Africa to find different types of Gladioli and after they married Rod decided to quit his job to join her on her travels.
South African born Rachel received dual citizenship after marrying British born Rod and the pair travelled the globe giving lectures on their passion and expertise on the Gladioli of South Africa.
In 1995 the couple set up Silverhill Seeds named after their home in Silverhill Crescent and built up a successful business working from home employing staff to sell their seeds around the world.
The trial continues.