Trellised Hoya pubicalyx ‘Red Button’

Origin and Description:
Hoya pubicalyx 'Red Button' is a unique cultivar selected by the late Genevieve McDonald from Merritt's Island, Florida, and was identified from seedlings growing in her garden. I found this information from a post on Gardenweb by "Lesli" in 2006, during my research in 2024. Unfortunately, I was unable to contact Lesli to confirm this information. According to Lesli’s detailed post, Hoya pubicalyx 'Red Button' has smaller leaves compared to Hoya pubicalyx 'Royal Hawaiian Purple', with less speckling. Contrary to what has been written elsewhere, some of the leaves do have speckling, though not as prominently as other cultivars.

The flowers are a particular highlight of 'Red Button'. The corona appears dark red or almost black, but this coloration is actually an illusion caused by dark red nectar being absorbed by the sponge-like material inside the corona. The corolla petals themselves are more or less white. In cooler weather, the sap fills the corona lobes gradually, making the entire flower appear evenly colored. However, in hot weather, the sap "boils over" and spills out unevenly before the flowers open, leading to variegation in the blooms. This phenomenon is less likely to happen outdoors, but when grown under glass, where heat can build up, the sap may overheat, leading to variegated flowers.

Note about Previous Sales:
I obtained my clone of Hoya pubicalyx 'Red Button' from Kartuz Nursery in Vista, CA, in 2018. Initially, I believed it was Hoya pubicalyx 'Royal Hawaiian Purple', so if you purchased a plant with that tag from me before September 2024, it is actually Hoya pubicalyx 'Red Button'.

Natural Habitat:
Although Hoya pubicalyx 'Red Button' is a cultivated variety, it shares the same tropical origins as other Hoya pubicalyx varieties, which grow as epiphytes in humid Southeast Asian environments. It thrives well indoors with the right care.

Care Instructions:

• Light: Prefers bright, indirect light. Leaves may take on a reddish tint in stronger light conditions, but avoid direct sunlight as it can scorch the leaves.
• Watering: Water when the top inch of soil dries out, and ensure the potting mix drains well to avoid root rot.
• Humidity: Moderate to high humidity (50-70%) is ideal, though the plant can adapt to household humidity levels. Misting or a humidity tray can help in drier environments.
• Temperature: The plant grows best in temperatures between 60°F and 85°F (15°C to 29°C). Avoid exposing it to temperatures below 50°F.
• Soil: Use a well-draining potting mix with orchid bark, perlite, and coco husk to prevent water retention.

Fun Fact:
The dark red or nearly black appearance of the coronas in Hoya pubicalyx 'Red Button' is due to dark red nectar being absorbed into the flower's corona, giving the illusion of colored petals. This process sometimes results in variegated blooms in hot weather, especially when grown indoors or under glass. The variegation is caused by overheating of the sap, making 'Red Button' a fascinating plant for collectors.

Thanks to Lesli's research, we have insight into this intriguing cultivar’s unique biology and bloom behavior.