Flaming katy (Kalanchoe blossfeldiana, Poelln. 1934)

Identity

Accepted under the name Kalanchoe blossfeldiana Poelln., this species belongs to the genus Kalanchoe in the stonecrop family, Crassulaceae. POWO/WCVP ties the name to a 1934 publication in Repertorium Specierum Novarum Regni Vegetabilis and gives northeastern Madagascar as its native range. ^{1 2}

The names flaming katy, florist kalanchoe and Christmas kalanchoe mostly describe the flowering pot plant. The epithet blossfeldiana honors Robert Blossfeld, the German nurseryman linked to the plant's introduction into horticulture, while the botanical authority is Poellnitz. ^{3 4}

Treat the name Calandiva with some care: it covers double-flowered horticultural forms, not a separate species. A Calandiva can look quite different in flower and still belong to the same horticultural group as K. blossfeldiana. ^{5 3}

Recognition

Expect a small, compact succulent clump, upright and branching. Horticultural sources usually give a potted height of 15–45 cm (6–18 in), with a dense or slightly rounded habit. The stems are thick and green and can stiffen with age. ^{3 5}

Leaves are opposite, simple, fleshy and glossy, oval to oblong, with a scalloped or shallowly toothed margin. That scalloped edge is a good clue for the common pot plant, but it will not identify every member of Kalanchoe, a highly variable genus. ³

Small tubular to bell-shaped flowers, often four-lobed in single forms, are held in terminal clusters above the foliage. Red, orange, yellow, pink and white are the usual commercial colors; the double forms look like miniature roses. ^{3 5}

Useful taxonomy

The binomial Kalanchoe blossfeldiana Poelln. is the fixed point. The following names show up in its synonymy or as older designations, and can still appear in databases and catalogs: ^{1 6}

• Kalanchoe coccinea (H.Perrier) Boiteau
• Kalanchoe coccinea var. blossfeldiana (Poelln.) Boiteau
• Kalanchoe globulifera var. coccinea H.Perrier

This synonymy accounts for part of the confusion with older retail names. For safety purposes the genus name still matters: the ASPCA and Merck issue warnings mainly at the level of Kalanchoe spp., while taxonomic databases pin down the exact species. ^{7 8}

Habitat and range

In the wild, according to POWO/WCVP, Kalanchoe blossfeldiana is a succulent subshrub of the seasonally dry tropical biome, native to northeastern Madagascar. The Trefle data consulted also give Madagascar as the native range and note several tropical introductions. ^{1 6}

A recent nomenclatural treatment fills in the background of the type material: Madagascar, the Tsaratanana massif, with a mention of lichen forest and high elevations, but also a history of plants cultivated by Perrier de la Bâthie before the herbarium specimen was prepared. That detail keeps "native to Madagascar" accurate without turning it into an oversimplified ecological map. ⁴

Beyond Madagascar, databases list Florida, southwestern Mexico, Nicaragua, Puerto Rico, Sardinia, Senegal, Turkey and Vietnam among its areas of introduction. No invasive status is recorded for mainland France; where winters bring frost, flaming katy is grown as a houseplant, in a sunroom or on a sheltered, frost-free balcony. ^{1 9}

Life cycle, flowering and cultivation

Indoors, its visible cycle is that of a perennial potted succulent. The plant can be kept after flowering if it gets a very free-draining mix, strong light that does not scorch, and infrequent watering. Overwatering kills more of these plants than the odd forgotten drink. ^{3 5}

Flowering depends heavily on day length. To bring on new buds, NC State recommends about 14 hours of complete darkness a day for at least 6 weeks in fall and winter. A classic plant physiology paper also describes Kalanchoe blossfeldiana as a typical short-day plant. ^{3 10}

Growers propagate it mainly from stem or leaf cuttings; the RHS also mentions sowing seed or dividing offsets in spring. To keep a double or variegated form true, cuttings are more reliable than seed. ^{3 5}

Toxicity and uses

Flaming katy is an ornamental, not a food plant. POWO notes medicinal and environmental uses, but the extract used gives no detail on plant part, preparation, dose or safety, so those mentions do not amount to usage advice. ¹

Its toxicity comes from bufadienolides, glycosides that act on the heart. The ASPCA lists Kalanchoe spp. as toxic to dogs and cats, with vomiting, diarrhea and, rarely, abnormal heart rhythm. NC State extends the warning for K. blossfeldiana to people, children and pets. ^{7 3}

Merck groups Kalanchoe spp. with the houseplants and ornamentals toxic to animals and links them to cardiac glycosides. For horses, historical data call for caution, whereas the ASPCA Kalanchoe entry explicitly names dogs and cats. The advice therefore stays cautious rather than claiming veterinary completeness. ^{8 7}

Cultivars and look-alikes

Commercial forms differ mainly in flower color and shape. NC State lists 'Flaming Katy', 'Kerinci', 'Lanin', 'Queen Jodie', 'Queen Lindsay', 'Simone' and Kalanchoe blossfeldiana f. variegata, among others. The RHS records many cultivars and notes that the image on its page shows the Calandiva series. ^{3 5}

Double forms, often sold as Calandiva, should not be mistaken for another species. They change the number and look of the petals, not the core needs: bright light, a pot with drainage holes, a free-draining mix, careful watering and long nights to trigger blooms again. ^{5 3}

Mix-ups usually involve other kalanchoes: Kalanchoe tomentosa, fuzzy and grayish; K. daigremontiana and K. delagoensis, which can carry plantlets on their leaves; or unlabeled hybrids. When in doubt, opposite scalloped leaves, terminal flower clusters and the full scientific name are more reliable than the word "kalanchoe" alone. ³

Main sources

• Plants of the World Online / Kew, Kalanchoe blossfeldiana Poelln.
• Royal Horticultural Society, Kalanchoe blossfeldiana
• North Carolina Extension Gardener Plant Toolbox, Kalanchoe blossfeldiana
• ASPCA Animal Poison Control, Kalanchoe toxicity entry
• Merck Veterinary Manual, houseplants and ornamentals toxic to animals
• Fredericq, 1963, Flower Formation in Kalanchoe blossfeldiana by Very Short Photoperiods
• Gallo & Smith, 2024, Kalanchoe blossfeldiana Von Poellnitz 1934