Here's what Brent Dickerson says:
"It was, at some time evidently roughly around the year 1800 or 1810, the custom of the inhabitants of the Indian Ocean island of Reunion, then called the Ile Bourbon, to mark off their land with hedges comprised of, as Monsieur Breon, a botanist of the time, put it, "one row of the Common China Rose [presumably "Old Blush"--that is, 'Parsons' Pink China'], the other of the Red Four-Seasons [presumably the red 'Tous-les-Mois' Damask Perpetual, which was common then]." One Monsieur Edouard Perichon found, when planting one of these hedges, a plant which appeared to be a hybrid of the two, and which was subsequently called, after him, 'Rose Edouard'. Here is a description of 'Rose Edouard' written in 1828, translated from Prevost fils' French: "This was the first one brought to France, and can be considered the Type of the species. Canes long and divergent, armed with much-hooked thorns, which are glandular at their base. Leaflets oval, large, cordiform at their base. Ovary oboid-oblong, glabrous and glaucous at the tip. Corolla medium-sized, hypocrateriform [i.e., "like an antique cup"], double or lightly double, intense and bright deep pink."
Evidently in 1819, Monsieur Breon sent to Antoine Jacques, gardener of the Duc d'Orleans at Neuily, near Paris, seed from 'Rose Edouard'. Five of these seeds sprouted in Spring of 1820, and two of these five "bloomed and rebloomed" in 1821. One of these two seedlings was illustrated by Redoute, who, as was his habit, gave it two names, a scholarly-sounding Latinate one ('Burboniana'), and another in the vernacular ('Rosier de l'Isle de Bourbon' [sic]). Here is how Redoute and his collaborator Thory described it in 1824: "Shrub, tall, vigorous, branched, bushy. Prickles large, hooked, wide, reddish. Leaflets 5 or 7, base rounded, acute at the tip, glabrous on both surfaces, simply dentate, glossy green above, paler beneath; petioles villose, with small sessile glands and tiny prickles; stipules decurrent, acute, denticulate. Flowers sweetly scented, many together at the ends of the laterals; pedicels finely glandulose; bracts elongate, ciliate, glandulose; receptacles ovoid, glabrous; sepals pinnatifid with subsetaceous prickles; petals 3-4 seriate, cordately notched, bright pink. Hips somewhat rounded, ovoid, red. According to the Duc d'Orleans, this rose [meaning by "this rose," confusingly, the *parent* of the rose they illustrate, as close reading will show] grows in waste places on Reunion Island. Seeds brought from there some years ago produced the plants in the Neuilly gardens from which our painting was made. It has a good habit, and the abundance of its blooms, sometimes almost single but mostly semi-double, and their fine color and perfume, make it a worthwhile adornment for landscape gardens."
Meantime, Breon also sent, in 1821, cuttings of the original 'Rose Edouard' to the gardener in charge of the hothouses at the Jardin des Plantes in Paris--Monsieur Neumann."
Supposedly they did have cuttings in 1821. However, Josephine had sent for the tea rose years previously, though she was dead in 1814.
Cafres (it's spelled with one f) translates to"African person taken to Reunion Island to be a slave", according to Wikipedia. I got the impression it may be an insult.
So the Plaine des Cafres means Plain of Slaves, maybe? Down the road is the Plaine des Palmistes, or Plain of Palms. It's beautiful. Up the road is the volcano.
All the pictures I found show what looks like a cow pasture on a hill running down to a valley. I saw one bush that looks like it had red hips, maybe. Leafless. I found another garden in Hellbourg with defoliated hybrid teas with a couple roses on top. Blackspot?
Now, If I had a bunch of slaves working a field, I suppose it could occur to me that edging these fields with thorny roses would keep them in.
Of course, Parson's Pink China is thornless, and scentless. Its value is the repeat blooming gene.
I couldn't tell from what pictures I found what sort of crops grow there, and its hilly edges looked difficult to hedge.
Yep, there's a hole in this story you can drive a truck through.
You can find the very interesting botanical articles of Jean Jacques Segalen by typing his name and Reunion Island into Google.