Native Plants of Hawai‘i - The Magic of LEDs

The Magic of LEDs

I (Koebele) am old enough to remember trying to grow African violets (and some other tropical houseplants) in the dead-of-winter under those funny-looking pink-light fluorescent tubes inside my fraternity room at the University of Michigan. The tubes (and their lamp ballast) were hot, expensive, always burning out too soon, and never seemed to help the plants survive all that well. Well, that all changed about ten years ago with the development and commercialization of the light-emitting diode (LED). (LEDs were actually invented all the way back in the 1960s, but it wasn't until recently that wide-spectrum white light LEDs were developed and production methods were created to make them cheap.) Today (2025), it is possible to buy four compact full-spectrum LED panels or strips (with about 80 LEDs each) emitting a mixed spectrum of light that closely mimics sunlight for about $25. They are lightweight, cool to the touch, use much less electricity than other types of lamps, and last a really long time (30,000 to 50,000 hours). And, most importantly, the plants really seem to 'like' them.

To maximize light intensity, each level of my plant stands have two LED panels (with about 80 LEDs each). Electric timers (near the floor) automatically provide 12 hours of illumination. Two or three large yellow sticky panels hang from each plant stand to control fungus gnats. To slow vegetative growth, most plants are potted in Bonsai trainer pots filled with 100% black cinders.

Over the past couple of years, I've been experimenting more and more with growing native Hawaiian plants indoors, discovering which species I can grow in my tiny condominium under LED lights. Here are some of my discoveries and suggestions to, hopefully, encourage you to give indoor native Hawaiian plant horticulture a try.

I have been able to grow nearly every species I have tried thus far. However, not all of them have proved to be suitable indoors for the long term (see #2). Below is my current indoor species list that I will amend as I try more and more plants.
Some of the species I have grown indoors were unsuitable long term because: (1) they got too large (e.g., naio) to conveniently place under the LED panels on my plant stands, or (2) their leaves got too large to properly display and care for (e.g., Delissea). Therefore, I now only try to grow species with smaller leaves. For species with large mature sizes but small leaves (e.g., lama, ʻōhiʻa lehua), I try to keep them small by growing them Bonsai style. (Actually, almost all the species I've grown have the potential to get too big, so I grow pretty much everything in small pots to purposely stunt them.)
I grow nearly all my indoor plants in 100% black cinders. This tends to slow their vegetative growth but not their flowering. And, I have far fewer problems with fungus gnats and harmful soil microbes.
While I want to slow the vegetative growth of my plants as much as possible, I still regularly fertilize them to improve their color and flowering potential. Recently, I switched to a "feeds-every-time-you-water" (10-15-10) liquid concentrate at its recommended strength (i.e., 7 drops per quart of water) because it gives me better control of my plants' growth. I do this by watering with the fertilized water until I see renewed color and growth. Then, I switch back to watering with fertilizer-free water to again slow the plants' growth.
My indoor plants are protected from threats like snails and slugs, mice and rats, and most harmful insects. However, I've discovered they are much more prone to infestations by spider mites, probably because there's no wind or rain to blow or wash these pests away.
With no rain, which many plants seem to really 'like,' I typically mist or wash my plants about once a month.
As part of my keep-them-small strategy, I routinely remove (i.e., prune) both healthy new stems and leaves as well as older (dying) leaves and flowers.
An electric timer keeps my plants under a constant 12-hours per day light schedule. However, since my plant stands are near a large curtained window, they get a bit more than 12 hours of light during the summer months.
LED panels are bright. Still, I try to maximize the amount of light my plants receive by installing as many LED panels as possible (2 to 3) above them, as well as keeping the distance between the panels and the plants small (12 to 18 inches [30 to 46 cm]).

Here are the species I have grown indoors under LEDs to date (Sept-2025):

Achyranthes splendens var. rotundata

Brighamii insignis — gets large quickly; large leaves

Ceodes brunoniana — gets large quickly; large leaves

Chenopodium oahuense

Clermontia kakeana — gets large quickly; large leaves

Coleus australis — has flowered

Delissea kauaiensis — gets large quickly; large leaves; has flowered

Diospyros hillebrandii

Diospyros sandwicensis

Euphorbia celastroides var. kaenana — does poorly

Freycinetia arborea — does poorly

Gossypium tomentosum — does poorly

Heliotropium anomalum

Ipomoea pes-caprae subsp. brasiliensis — does poorly

Jacquemontia sandwicensis — has flowered

Lycium sandwicense — does poorly

Metrosideros macropus

Metrosideros polymorpha

Metrosideros rugosa

Myoporum sandwicense — gets large quickly

Myoporum stellatum — gets large quickly

Paratrophis pendulina — has flowered

Peperomia tetraphylla — has flowered

Plumbago zeylanica — has flowered

Portulaca lutea — has flowered

Portulaca molokiniensis

Portulaca sclerocarpa — has flowered

Portulaca villosa — has flowered

Scaevola coriacea — has flowered

Scaevola taccada — gets large quickly; large leaves

Selaginella arbuscula — kept in a glass jar

Sesbania tomentosa

Sesuvium portulacastrum — has flowered

Sida fallax — has flowered

Solanum nelsonii — has flowered

Tetramolopium filiforme — has flowered

Vitex rotundifolia — has flowered

Wikstroemia uva-ursi