A very dark variant of Begonia nigritarum

Begonia nigritarum is one of the most widespread Begonia species in the Philippines, with so many variations in leaf color and size, and rhizome behavior. Most variants have marked leaves and creeping rhizomes, but one population within my area exhibit very dark leaves that blend with the dark volcanic rocks the plants cling on. Additionally, the rhizomes are very short and compact, which is probably explained by the deciduous nature of the plants. If these plants weren't so, the rhizomes have the potential to elongate indefinitely and will be limited in their length only by age.

During the dry months, the plants die back to dormant rhizomes which are protected from further desiccation because these are tightly appressed on the underlying rock. That the plants are in shaded locales help too; I have never seen the population ever receive direct sunlight, irrespective of the time of the year.

Other plants of this species from other populations also experience a dry period but do not go dormant, or at the most, shed the largest leaves and retain the smaller, apical ones. Furthermore, in most of these populations, the plants receive filtered light which probably influence the vigor and sizes they attain. Such plants, not surprisingly, grow much larger. Shown below is an example of one of these larger-growing B. nigritarum:

The leaves, apart from being larger, are greener with more extensive, though subdued, markings.

In contrast, the leaves of the plants from my area's population are plain and dark, but there are others too with sparse, pale dots. Notice the flatter and matted leaves, and the less robust and lush growth of this flowering specimen below.

Shown below is one of those plants with plain dark foliage:

 The leaf undersides of these begonias are red, which is very apparent when one looks up to the uppermost plants:

This variant of B. nigritarum probably would make interesting additions to a serious Begonia collection, but perhaps not for casual gardeners. Its deciduous nature may put off those who would like their plants evergreen. Nevertheless, the small size of the plants and the dusky purple leaves that age to pink would be too much for the die-hards to resist, I would guess.

I have seed-grown plants from this population and even in cultivation, this deciduous behavior is retained. It is not unusual to find their pots appearing empty during the dormant stage. However, when the rainy season begins, the rhizomes almost immediately produce new leaves and resume growth.

If truth be told, I am not too keen on eventually propagating lots of these plants for introduction to mainstream cultivation as demand would probably be lukewarm at best. I'll just enjoy seeing them in my little garden and in their native haunts.