What follows below is a short list of several species that have a wonderful aspect to their morphology; they just happen to have ridiculously large flowers, either in fact or in proportion to themselves (perhaps it’s the same as in ants and other smaller creatures, which are able to lift many times their own body weight, that only smaller plants can grow a flower that is larger than the rest of the plant). These are all species that can be grown indoors, though some are more challenging than others.
Epiphyllum oxypetalum and related species
One of the many plants with the common name ‘queen of the night’ (and also known as ‘orchid cactus’ ‘Dutchman’s pipe cactus’ or ‘night-blooming Cereus’), E. oxypetalum is an epiphytic cactus native to Mexico and a good part of Central America. It produces dinner-plate sized white flowers that open for a single night and are heavily scented. This plant grows easily enough in a pot or hanging basket, and will bloom well enough indoors if care is up to snuff. It is pretty rambly by nature, and can get awfully large if you give it room, though it is easily pruned to shape, and at least the stems are spineless, which makes brushing past one in a tight space not as uncomfortable as it might be with some of its close relatives.
I know that terrarium gardening has been a fad of late, but I fear that the concurrent popularity of succulent plants may cause people to be frustrated by limited success with terrariums (this being for the simple fact that succulents by their very nature are not good candidates for terrarium culture); more on that whole thing later, but in the interest in promoting terrariums as an actually quite easy way to grow plants and have them do well (read grow well and flower), I would like to make Sinningia pusilla the poster child of terrarium gardening.
This species has everything to recommend it; they are adorably tiny (leaves are around 3/8″ long), have fuzzy, somewhat iridescent foliage, and, best, throw huge (relative to the plant, at least) pale tubular flowers. They self-pollinate and are quite prolific, able to quickly start colonies of seedlings that form an attractive ground cover. They also are quite easy to grow if provided with one thing above all: humidity. Enter the terrarium; given the added humidity, these plants will flourish when the soil is kept reasonably moist; if allowed to dry too far or too long, they will go dormant, reducing themselves to a tiny tuber to await the return of more favourable times. They are also fairly undemanding of light, which sets them worlds apart from succulents and other plants commonly toted for terrariums.
This species and S. pusilla above both belong to the family Gesneriaceae, which contains a great many species well suited for growing indoors, of which the ubiquitous African violet is a familiar one. Columnea is a large genus with much variety, but Columnea microphylla has to be one of the most impressive. Again, it is not the largest plant (the one to the left looks like it’s in a 3″ pot), but the red flowers absolutely dwarf the leaves.
This species makes a great hanging basket plant, and the pendant stems will trail downward and show off their freakishly large flowers. This one will need a fair bit more light than the Sinningia above to bloom well, but won’t take up much space in a sunny window.
A first glance of the foliage and you might want to call this one a cactus, but not only is it not one of those, in fact its more familiar relatives are Hoyas, the tropical vines native to Asia commonly grown as houseplants, as well as the common milkweeds here in Ontario which are the chief food supply for monarch butterfly larvae. Stapelia is a genus restricted mostly to southern Africa, and so need a cooler rest period over the winter. making them a good candidate for a bright but poorly insulated bay window in a century home, say. The flowers can be up to a foot across, but have the unfortunate characteristic of reeking of rotting meat in order to attract flies, which are their natural pollinator. A beautiful plant to be sure, but I suppose not for the faint of heart; perhaps I should recommend that this one be brought outside in summer.
I’ve saved the best for last, and this little one is, to me, one of the most incredible orchid species out there, despite being only a couple inches across.
Lepanthes telipogoniflora is a diminutive orchid endemic to Colombia, where it grows in some of the wettest rainforest on earth (one spot once reported 43 FEET of rain in a year), which gives us a pretty fair hint as to how it should be kept in cultivation. Alas. I have personally killed this plant (twice); it understandably does not take to drying out in the slightest, and small plants are completely unforgiving. Enter again the terrarium; many people grow this plant successfully in those little round glass hanging terrariums that are quite easy to find these days, and as long as they’re kept happy (you’ll know it is so because the plant won’t be dead) they will bloom pretty consistently, with the flowers being relatively massive and at least the size of the plant in younger specimens. Another important cultural note is that they, as are many of the Pleurothallidinae orchids, are intolerant of hard water, and require rain or otherwise filtered water to do well. This species is, so far as I know, not produced by any Canadian orchid nurseries (presumably because of the aforementioned cultural challenges), but is brought in by Ecuagenera when they attend regional orchid shows here, and presumably by others as well.
This list of huge bloomers is by no means exhaustive; in fact, I’m sure I’ve only scratched the surface. If any other plants fit the bill, list them in the comments below!