Hoya krohniana ‘Black Leaves’

A dark-leaved Hoya krohniana selection

‘Black Leaves’ is a cultivated form whose foliage deepens towards dark olive or purple-green. Hoya krohniana is a small-leaved trailing epiphyte native to the Philippines.

Care for Hoya krohniana ‘Black Leaves’

• Placement: Choose a bright site with gently filtered direct sun. Stronger filtered light may deepen the dark leaf colour, but dry bleached patches show that exposure increased too quickly.
• Watering and root mix: Check the mix below the surface before watering, because a firm leaf can hide a dry or waterlogged root ball. Its fine roots need a short dry interval without becoming crisp, and the centre of the pot must not stay saturated. Pot into an open blend with smaller bark and mineral structure, leaving air spaces around the roots. Use enough smaller material to keep roots in contact with the substrate.
• Trailing growth: Keep the fine growth elevated where stems will not rub on a hard edge. Keep firm flower spurs when arranging the trailing stems, because the plant can bloom from them again.
• Airflow: Avoid leaving the mix around the roots against cold glass or in motionless humid air. Use moderate humidity with enough airflow for the foliage to dry.
• Feeding: Reserve dilute balanced nutrition for periods of visible root and stem growth. Allow more time between applications when new growth pauses.
• Fine trailing growth: Keep the small leaves clear of dense wet moss and let the stems branch freely over the pot edge or a light support.

Common issues with Hoya krohniana ‘Black Leaves’

• Leaves lose firmness while the mix remains dampLikely cause: The container is holding water around compromised roots for too long.What to do: Slide the root system free and trim away all dark decaying roots. Set the cleaned roots into a smaller pot, keep the base of the vine clear and wait until the mix has dried sufficiently before rewatering.Urgent warning: Remove a firm green node for propagation while the stem is still unaffected.
• A new dark leaf develops a bleached centreLikely cause: A hot window raised leaf temperature and produced local dehydration.What to do: Filter the light with a sheer curtain or increase the distance from the glass. Keep the dark leaf unless the damaged area becomes wet or enlarges; then remove it at the petiole.
• New small dark-stemmed leaves emerge twisted with black specks or silvery scarsLikely cause: The unopened blade is harbouring feeding thrips.What to do: Quarantine it, rinse the upper and lower leaf surfaces and cut away ruined tip growth. Patch-test insecticidal soap, treat according to its label, and use a blue trap to catch adult thrips.
• Dark foliage becomes olive greenLikely cause: Light is lower than before or the leaf has not finished hardening.What to do: Keep the affected leaf unless it softens, becomes wet or develops spreading damage. Softness, dryness or spreading edges indicate a real tissue problem.

Hoya krohniana ‘Black Leaves’ and pet safety

Hoya krohniana ‘Black Leaves’ is treated as non-toxic to cats and dogs. Chewing leaves or stems can still cause temporary drooling, vomiting or diarrhoea. Keep the plant out of reach of pets that chew foliage, and contact a veterinarian if symptoms are severe or persistent.

Why it is called ‘Black Leaves’

The cultivar name refers to mature foliage that deepens from green and olive towards a very dark purple-green as it hardens.