Caltha introloba F.Muell.

Nomenclature and Growth Habit

Caltha introloba F.Muell., commonly known as the alpine marsh-marigold, is a small, hairless perennial alpine herb with short, stout rhizomes that forms dense mats.

Leaf Structure

Its leaves have petioles approximately 5 cm long, and leaf blades that are oblong, lanceolate, or rounded-triangular, measuring 8–40 mm long with an emarginate tip. The upper surface of each leaf bears two lanceolate-triangular appendages 4–20 mm long.

Flowering Stem Development

The flowering stem is 1–2 cm long when flowers first open, and grows to 5–10 cm by the time seeds are ripe.

Sepal Characteristics

It has 5 to 8 sepals 10–22 mm long, which are white but often tinged with pink or purple, especially at the base and along the veins.

Reproductive Organ Morphology

15 to 30 stamens with white or often pinkish filaments and yellow pollen surround 6 to 18 free carpels. When mature, these carpels develop into spreading follicles with short beaks that contain few seeds.

Initial Flowering Period

Flowering takes place between November and December, often directly from beneath receding snow.

Geographic Range

Caltha introloba is found in Victoria, New South Wales, and Tasmania, where it grows in alpine areas.

Specific Habitat Locations

It occurs on the slopes of Mt Kosciusko, and is locally common in sites with late-lying snow and between moss on high ranges including the Baw Baws, Snowy Range, Mt Buffalo, Bogong, and Dargo High Plains.

Flowering Habitat

It typically flowers at the edges of receding snow drifts.

Associated Species

In Victoria, Caltha introloba grows alongside Brachyscome tadgellii, Carex gaudichaudiana, Carpha nivicola, Drosera arcturi, Oreobolus distichus, and Schoenus calyptratus.

Flower Bud Development Timeline

Flower buds begin developing in mid-January, the middle of the southern hemisphere summer, and are fully formed by May, when fresh snow no longer melts. Most flowers open after snow melts in October, though some flowers will open under persistent snow cover if it lasts until mid-November.

Seed Maturation Timeline

Seeds are typically fully developed by the end of summer, in February.

Flower Formation Trigger

Experiments have shown that flower formation is triggered by long days and strong light.

Flower Opening Requirement

Flowers will only open after a cold period, which is likely a mechanism to prevent premature opening in autumn.

Seed Germination Temperature Requirements

Seeds of Caltha introloba germinate best at temperatures between 22 and 27 °C, after a delay of 40–60 days, and hardly germinate at temperatures between 0 and 15 °C. After four months at 1–2 °C, however, germination below 15 °C is much faster and more successful.

Germination Timing Implication

This means seeds shed in summer are unlikely to germinate before snow melts the following spring.

Optimal Growth Temperature

Growth and photosynthesis are optimal around 15 °C, which is near the mean maximum summer temperature in the alpine conditions where this species grows.

Photosynthesis and Growing Season

Photosynthesis also occurs at 0 °C, so the growing season likely includes the entire period when plants are not covered by snow.