Flaming Katy

Identification and origin

Kalanchoe blossfeldiana belongs to the stonecrop family, Crassulaceae. It is native to northeastern Madagascar. Its name honors Robert Blossfeld, a German nurseryman who found it on the island and brought it to Europe in the early 1930s.

It is a perennial succulent, upright, well branched and compact, forming a small dense mound 6–18 in tall and 6–12 in wide. It grows slowly. The stems are thick and green; the leaves are fleshy and glossy as if waxed, dark green, oval and scalloped along the edge, 2–4 in long and about 2 in wide.

The flowers are tiny, tubular and four-petaled, less than 1 in across, and gathered into broad clusters. They come in red, orange, yellow, pink, magenta and white, in single or double forms; doubles can have up to twenty-six petals. It blooms naturally from late winter into spring; the display lasts about a month, longer when nights are cool. Outdoors, the flowers attract bees, butterflies and hummingbirds.

Garden centers mostly sell selected series: ‘Simone’ with pure white flowers, ‘Lanin’ in bright orange, ‘Kerinci’ in pink, ‘Queen Jodie’ with double salmon-pink flowers, ‘Queen Lindsay’ with double golden-yellow flowers, bright red ‘Flaming Katy’, and a form with variegated foliage.

Light

It needs a lot of light to stay compact and bloom: in dim light the stems stretch and turn spindly. In winter, place it in a sunny south- or west-facing window. In summer, a very bright spot with a few hours of direct sun suits it, but prolonged, intense sun can scorch the leaves: shade it from afternoon sun.

To set new flowers it needs six to eight hours of bright light a day, in addition to the long nights described below.

Watering

As a succulent, it tolerates drought well and fears overwatering above all. Let the mix dry between waterings, without waiting for the plant to wilt, then water thoroughly until water runs out of the bottom of the pot. Always empty the saucer or pot cover: roots left sitting in water rot quickly.

Feel the soil before each watering instead of following a fixed rhythm: the root ball does not dry at the same speed depending on season, heat and pot size. Overwatering causes root rot or stem rot.

Potting mix

Choose a very free-draining mix, such as a cactus and succulent mix, or roughly three parts peat or a peat substitute to two parts perlite. pH matters little: it tolerates acidic, neutral or alkaline mixes. The pot must have a drainage hole.

When the plant is actively growing, apply a houseplant fertilizer about once a month.

Temperature

It prefers about 61 °F at night and 70 °F during the day. It accepts cooler nights, down to 45 °F, and days of 50–70 °F; cool nights noticeably extend the life of the flowers. It does not tolerate frost.

It can spend the summer outdoors in a bright, lightly shaded spot once all danger of frost has passed: acclimate it gradually to avoid burning the tender leaves. Bring it back inside before temperatures drop to 45 °F. In the ground it is grown only in USDA zones 10 to 12, where it serves as a groundcover or rock garden plant.

During the long-night period that sets the buds, avoid temperatures above 81 °F: heat delays flowering.

Repotting

After flowering, cut off the spent stems and move the plant into a pot just slightly larger, using a free-draining mix. Then set it in a warm, sunny window.

Pruning

After flowering, cut tall, leggy stems back by about half and remove the faded flower stalks.

Reblooming depends on night length: it is a short-day plant, like the poinsettia. In fall and winter it needs about fourteen hours of total darkness each night for at least six weeks to form buds. The natural days of that season are enough, as long as no lamp comes on in the room in the evening; otherwise, put it in a closet each evening and bring it out in the morning. Once buds are visible, lighting matters less. Started in early fall, this treatment brings flowers around midwinter.

Propagation

Stem cuttings are the easiest method, in spring or early summer. Take 2–3 in tips from non-flowering shoots with two pairs of leaves, remove the lower leaves and let the cut end dry for several days to callus. Then insert them in an equal mix of peat or peat substitute and perlite; no rooting hormone is needed. Roots form in two to three weeks. Leaf cuttings also work.

Common problems

• No flowers: nights not long enough or interrupted by a lamp, too much heat while buds are forming, or not enough light.
• Stretched, weak stems: insufficient light.
• Plant collapsing, dark brown stem base: root and crown rot, caused by overwatering or a soilborne fungus; use fresh potting mix and discard affected plants.
• Tan patches or white powder on leaves: powdery mildew; improve air circulation.
• Mottled leaves, yellow spots or ring patterns, stunted plant: a virus; discard the plant.
• Pests: mealybugs, scale insects, aphids and spider mites; remove them with a cotton swab dipped in rubbing alcohol or by hand.
• Scorched leaves: sun too strong after a change of location.

A single symptom can have several causes: consider watering, light and temperature together before treating.

Toxicity

All parts of the plant, flowers, leaves and stems, are toxic to dogs, cats and people. They contain bufadienolides, compounds that act on the heart. Eating it causes nausea, vomiting, diarrhea and lethargy and, less often, abnormal heart rhythms, which can be fatal in pets. Keep the plant out of reach of children and animals, and if ingestion occurs, contact a veterinarian or a poison control center right away.