Photo caption: Dischidia ovata in a terrarium under intense light.
Q: I have a Hoya whose leaves have turned quite red. While pretty, I want to make sure I’m not stressing the plant too much. How can I tell?
A: If growth is progressing normally and there aren’t any other concerning symptoms (like leaf drop beyond the typical shedding of old leaves, or stunted growth), then I would say you’re at a tolerable level of stress for the plant. Reddening foliage is sometimes referred to as “sun stress” by houseplant growers, and it’s the plant’s natural response to intense light by generating sunscreen pigments to protect the leaf tissues.
Some species or cultivars of Hoya and their Dischidia cousins can turn ruby-red or rose-blushed if grown in bright light. I’ve grown cuttings propagated from a single Watermelon Dischidia, Dischidia ovata, in different light levels, and some will stay green in lower light and others turn varying degrees of red in higher light. In one case, under a bright spotlight over a terrarium, the plant turned completely ruby on every surface exposed to light. Even across a single leaf, areas in shadow can remain green while the rest blush red, as they did when I peeked beneath one leaf that was partially covered by another.
I have a ‘Sunrise’ cultivar of Hoya in a pot hanging underneath the edge of LED grow lights. The half of the plant growing close to the lights is red, and the half receiving much less light on that outer half is green. If anything, I’d say that the redder side grows more vigorously.
Other houseplants can also redden if grown at the higher end of their light level preferences, such as certain begonias and bromeliads. In other cases, over-lit foliage bleaches to a paler or yellower color, so not every indoor plant can adapt to stronger light.
Sometimes you just might need to experiment to see how a plant reacts, and keep in mind that other factors (nutrient availability, soil moisture level, ambient temperature and humidity) which might be causing plant stress can complicate your assessment of how a plant is faring based on light level.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.
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That’s quite a bed of moss you have there! What kind of moss(es) is it?
Hi Ria! It’s live sphagnum moss. Sometimes the dried sphagnum (the same type sold for potting orchids) can “reanimate” if kept humid, in good light, and moistened with fairly pure water. I generally use distilled water for terrariums so the minerals don’t build up, and I imagine spores grew into new plants over time.