There is evidence that the Plants had a cultural connection to an illegitimate Longspée-Audley line of feudal lords who descended from the first Planatgenets. However, this is less well known to popular culture than a modern fiction about a blood-link of the Plant name to Plantard.
A popular and controversial myth is circulating about the origins of the Plant bloodline. The plot of the international bestseller, the 2004 book The Da Vinci Code (DVC), by Dan Brown, is derived from the pseudo-history contained in the 1982 book The Holy Blood and the Holy Grail (commonly abbreviated to HBHG) which was written by the British authors Baigent, Leigh, and Lincoln. In turn, much of the plot of HBHG was inspired by the so-called Dossier secrets of the Priory of Sion, which were deposited in 1967 in the National Library of France at Paris. These secrets alleged that living descendants of the Merovingian kings were the Plantard family, with a branch in England called Planta.
In the Dossier secrets, the Plantard family was said to include Bernard Planta-Pilus (Plantevelu). It was said to have descended from the Merovingian king Dagobert II. The family is said to have been exiled to Brittany after a failed uprising against Louis II in 881 such that, by the late 9th century, Merovingian blood had flowed into both Aquitaine (now Western France) and Brittany (now NW France). Though it is true that evidence exists for the Plantard family in Brittany as well for the spelling Plante in Brittany in the 16th to 19th centuries, most academics consider that the Dossier's genealogy for Plantard and Planta is an elaborate hoax.
The authors of HBHG also made a particularly inept family link between this Plantard genealogy and the Plantagenets. Indeed, there was even a connection of the Dossier secrets to the de Warenne relatives of the Plantagenets, who have been associated (to an extent) with the Plant family. It was alleged that the fifth Grand Master (1336-51) of the Priory of Sion was Jeanne de Barre (1295-1361), who was Edward I's grand-daughter and Edward II's niece, and who was betrothed to the last de Warenne earl of Surrey in 1306.
The originating Dossier secrets of Merovingian descent have been associated, by many, with right-wing French nationalism. For the benefit of an English audience, this was embellished with a heresy of Christian notions by the authors of HBHG and in the further book The Messianic Legacy. Though repudiated by Pierre Plantard (1920-2000) of the Priory of Sion, Plantard descent from the Merovingian kings was elaborated in the book HBHG such that it had stemmed from a concealed marriage between Jesus and Mary Magdalene. A still wider audience has now been reached with Dan Brown's fiction (DVC), which emphasises the descent to Plantard of the `sacred feminine' of Jesus' apostle of the apostles, Mary Magdalene.
The link from Mary Magdalene to the Merovingian kings has attracted particular disbelief, though its aspect of the `sacred feminine' has attracted some serious attention from female academics in America for example:
There is no question that Sigisbert existed and that he was Dagobert's heir. According to all sources other that the `Prieuré documents', however, it is unclear what happened to him ... There is no record of Sigisbert's death. Nor is there any record - apart from the evidence in the `Prieuré documents' - of his survival ...Indeed, there has even been some dispute about whether this Sigisbert existed at all. The tradition that he did comes from a record of the tenth-century life of St Arbogast, where it states that Dagobert II married Mathildis and had by her a son Sigisbert; however this source has been questioned as being too late and it has been argued that there could be a confusion with Dagobert I, his wife Nanthildis and son Sigebert. In any event, the tradition is that Sigisbert is the son of Dagobert II and his wife Mathildis, not of his subsequent wife Giselle de Razes whose existance is the claim of the `secret Priory documents' and from whom the the title of the counts of Razes is claimed to descend though a so-called Plantard family.
An association has been made for Plantard with the Messianic prophecy of Isiah 53:2: For he shall grow up before him as a tender plant, and as a root out of a dry ground. However, it should be noted that the early meaning of plant is simply `shoot' and the metaphorical association of `shoot' or `offshoot' with `offspring' is widespread. This metaphorical association is the basis of a possible early meaning of the surname Plant, such that Plant might simply mean `offspring', rather than there being any allusion to a specifically divine descent for the name Plant or Plantard. More simply, a 2016 surname dictionary gives child as one of four possible meanings for the surname Plant(e).
Though there is evidence for just a cultural connection between Plant and Plantagenet, other conjectures of family ties between different Plant-like names are (as yet) unproven:
French origins of Plant Name