When botanists say “it’s a bignon” (big-nōn), we are talking about a particular group of plants, shorthand for saying “and you know what that means”. It’s like saying “its a Chevy”, with the certain knowledge people will know something about the car based on the brand legacy.
“Bignon” is the botanical nickname for a distinct, easily recognizable mostly-tropical plant family called the Bignoniaceae. You’ll find vining bignons (Pyrostegia, Distictis (Amphilophium), Bignonia, Campsis) and their woody relatives (Jacaranda, Catalpa, Tabebuia, Tecoma) commonly planted in SoCal landscapes. We know them by reliable characteristics easily spotted when plants are sporting their masses of good-sized, tubular, trumpet-shaped flowers.
That’s most obvious in the spring and early summer landscape, which is brightened sequentially by fabulous displays of the pink-flowered tree, Tabebuia heptaphylla,* overlapping the bright golden-yellow T. chrysotricha, and culminating when the blue-purple Jacarandas come into flower in May through June. All of these trees show the suite of characteristics that clue us in to this family.
Take one of the pink tubular Tabebuia flowers in your hands and gently pull the corolla (the tube of petals) apart. Each tree has lots of flowers, and they are short-lived, so don’t feel guilty. Tearing it open and you’ll find the flower has four stamens in two pairs, of different length. The stamens do a crazy thing; their anthers cling together in pairs, and in Tabebuia, the stalks (we call these filaments) arch out – I tell students they are bow-legged.
Tabebuia isn’t alone; most bignon anthers do this to some degree. I’m including photos of Distictis ‘Rivers’ flowers, so you can see them up close. Below those images, check out stamens in flowers of Africa’s Sausage Tree, Kigelia africana.
As spring warms toward summer, the Jacarandas take center stage throughout Southern California, with mature specimens flowering in advance of the green appearance from their doubly-pinnate leaves.
For years I had guessed Jacaranda flowers are typical bignon productions – a tubular corolla with two pair of stamens and a long style with bilabiate (two-lipped) stigma. But taking a moment to investigate further, I found a wonderful surprise… Each Jacaranda flower hosts a feather-duster like structure, a Dr. Seuss-style staminode (a sterile, fifth stamen) topped with a hairdo of purple trichomes (hairs).
Thankfully, I was able to find a research article that explains this amazing (and handsome) organ has a role in pollination,** with some assumption it impacts the size of visitors. My own observation suggests this decorative structure is really a distributer, ensuring the white pollen thoroughly coats any visitor.
Presence of both stamens and a pistil tells us that Bignon flowers aren’t just handsome, they are perfect – a botanical term signaling the fact that flowers include both sexes. As is easily seen from the photos, the pistils have their particularities, producing long styles tipped with a stigma that looks like a tiny pair of lips. You can see the stigma in the enlargement of Pyrostegia flowers, just below (see Aurantiacum for more info on Pyrostegia.) Unveiling this combination of paired stamens and the curious stigma gives near faultless identity for bignons.
Once you are almost certain the plant you are examining is a Bignon, there are other clues to check for back-up. You’ll find, down along the stem, the leaves attach in pairs or triples at the same branching point (the node,) and the leaves are nearly always compound (each leaf has several leaflets.) The vines provide nice foliage and flowers, but we grow the trees mainly for their seasonally colorful flowers. For SoCal gardeners, this is a great group of vines and trees. They are easy, colorful, and given to drama.
Taxonomic Entanglements: When botanists name a plant family, they follow a formula based on the spelling of a core genus, normally the earliest genus described. Simply add “aceae” to the feminine plural form of the generic name. The genus Bignonia thus becomes the base for the family Bignoniaceae, just as Orchis is the base for Orchidaceae and Cactus is the base for Cactaceae.
So how did Bignonia get such a cushy role, providing the handle to an entire plant family, a really nice family? As we’ve done before, we look to Linnaeus, and everything around him. In 1719, French botanist Joseph Pitton de Tournefort described a group of newly discovered related plants from the Americas, establishing the genus Bignonia in honor of his supporter Jean-Paul Bignon (more on Jean-Paul later). Linnaeus accepted Tournefort’s names in the first edition of Species Plantarum. Since the Linnaeus work (1753) is the beginning of scientific plant names, he gets credit for Tournefort’s names (sorry, J. P.).
Two and a half centuries later, the matter of Tournefort’s and Linnaeus’ genus (and therefore the name of the family) remained in limbo, only to be resolved in a 5-page, complex article by Robert Wilbur (1980), an article that began with an 1865 quote from Berthold Seeman: “It is really high time that botanists should come to some understanding about what is to be regarded as the type of Bignonia.” Wilbur’s conclusion was that Bignonia is tied to Linnaeus’s (i.e. Tournefort’s) Bignonia capreolata, which means the genus survived taxonomic challenge, salvaging the family name from taxonomic purgatory.
So what about Jean-Paul Bignon, the person whose name the genus honors? Jean-Paul, of course, had little interest in plants, and never saw or grew any of the plants named for him. He was a famed orator who also happened to be Librarian to Louis XIV. From that position, Bignon exercised considerable influence. One fallout of his vision was the Bignon Commission, which set in motion the compilation of an encyclopedic record of France’s arts and trade crafts, an important publication of 113 folio volumes, Descriptions des Arts et Métiers, faites ou approuvées par messieurs de l’Académie Royale des Sciences, the printing of which began in 1761, ending in 1788, on the eve of the French Revolution.
Perhaps more profound for popular culture, Jean-Paul Bignon was patron to Antoine Galland, the famed French translator who first brought One Thousand and One Nights (Arabian nights) to Westerners, with a 12-volume translation (1704-1717) of ancient Arabic manuscripts. In its rare books, The Huntington holds editions of Galland’s translation. Even more exotically, in the Rare Books stacks you’d find the first printed Arabic version (1835) of Arabian nights, the personal copy of Richard Burton (who disagreed with Galland’s translations as having left out the more salacious scenes.)
*If you choose, you can use the segregate genus Handroanthus (described in 1970 for the Brasilian botanist Oswaldo Handro) instead of Tabebuia, in which case the pink tree would bear the name Handroanthus heptaphyllus. Changes such as this drive horticulturists crazy. Any reference source would link the two names, so I continue using Tabebuia because I like the sound of the name, it’s the standard in local horticulture, and it’s based on indigenous Tupi words “tacyba bebuya.”