Hillia triflora is a somewhat obscure epiphytic shrub in the coffee family, Rubiaceae. I didn’t know it existed until I ran across a small cutting for sale on eBay a few years ago, and after a quick google search, I made certain that I would be the high bidder when the auction ended. It’s a hummingbird-pollinated plant, and as I have noted before, this gardener is attracted to the same floral features that attract hummingbirds.
H. triflora comes from central America, with specimens collected from southern Mexico to Colombia, and although it usually grows at higher elevations, plants have been found at only 100 m above sea level in Costa Rica . As might be expected from this wide geographical and altitudinal range, the plant seems to be quite tolerant of both summer heat outdoors and cool winter nights in the greenhouse. There are two subspecies with overlapping range, H. triflora subsp. triflora, and H. triflora subsp. pittieri; judging by the equally sized leaves on flowering shoots and narrow, uninflated flowers, my plant belongs to the nominate subspecies .
The growth habit of this plant is very interesting. It forms an open shrub with flexible, infrequently branched stems bearing opposite, semi-succulent leaves. Each stem terminates with a protective sheath. Over the course of a couple of months, the sheath slowly swells and eventually splits, revealing that it was formed by a pair of bracts tightly pressed together. Emerging from the sheath is either a new stem segment with a pair of leaves and new sheath, or a cluster of (usually three) flower buds. At the base of the flower buds is one or more new sheaths, so the stem sometimes branches after flowering.
The roots of H. triflora are fibrous, without obvious adaptations to epiphytic life, and plants in habitat are occasionally found growing terrestrially in leaf mould or rotting wood . Consequently, I added some coarse peat to the mix of orchiata bark and perlite in which I potted my plant. I water when the mix is almost dry, and so far the plant seems happy. It grows with my vireyas under shade cloth in summer and goes back in the greenhouse when temperatures drop below 50 F (10 C) at night.
The flowers of H. triflora are very similar to those of the unrelated coral honeysuckle, Lonicera sempervirens (Caprifoliaceae), that grows wild in the woods around my house–it’s a remarkable case of convergent evolution driven by birds. I would guess that the hummingbird responsible for pollinating H. triflora is roughly the same size as the ruby-throated hummingbirds (Archilochus colubris) which pollinate L. sempervirens. I suppose it is even possible that A. colubris is a pollinator of H. triflora, given that the birds over-winter in central America and H. triflora has flowers in November/December as well as March-May .
I have previously featured a variety of hummingbird pollinated flowers on this blog, both native plants (Aquilegia canadensis, Aesculus pavia, Lobelia cardinalis, Lonicera sempervirens, Spigelia marilandica, Silene virginica) and tropicals (Juanulloa mexicana, Macleania sp. aff. smithiana, Macleania pentaptera, Ceratostema glans, Cavendishia capitulata, Bouvardia ternifolia, Bessera elegans, Behria tenuifolia, Columnea microcalyx, Columnea crassifolia). These flowers share obvious characteristics: bright red/orange/magenta color, tubular (or sometimes bell-like) shape, lack of fragrance, and copious nectar. The same features are seen in plants from Africa, Asia, and Australasia where there are no hummingbirds. In those locations, sunbirds (Nectariniidae) and honeyeaters (Meliphagidae) fill much the same ecological niche. However, because sunbirds and honeyeaters are less likely to hover than hummingbirds, bird-pollinated flowers in the old world are usually not pendant and are often attached to a stout inflorescence that allows the birds to perch (see, for example, Cyrtanthus obliquus).
- Taylor, CM (1989). A revision of Hillia subg. Ravnia (Rubiaceae: Cinchonioideae). Selbyana 11: 26-34.