I've been studying, with a degree of anticipation, the development of flower buds on the mauka 'roja' plants which Frank van Keirsbilck gave me last summer. They spent the winter confined to a windowsill in a fairly cool room; a few weeks ago I noticed that some of the stems were elongating into what I optimistically took to be inflorescences. Daylength at the time was probably a bit less than 12 hours, which suggests that mauka requires short days to initiate flowering.
The waiting is now over - a couple of flowers have opened in the last few days. The 'blanca' plants, located in a warmer spot, have grown much bigger and show no signs of flowering. I'm pondering on the significance of this observation.
The flowers are not the most photogenic objects I've ever pointed a lens at, but like those Elizabethan miniatures, they repay closer investigation. I just wish I hadn't mislaid my hand lens when I needed it most; like as not, it is lying buried beneath a pile of festering oca stems and tubers and will resurface via the compost heap at some future date.
I won't be entering this image for the Henri Cartier-Bresson Award, but at least you get an idea of the flower's petite, pink appearance. The anthers have, relatively speaking, whopping great big pollen grains. I tried to shift them onto the stigma, but I fear my clumsy fumblings did more harm than good. The buds themselves are covered with sticky hairs. Imagine my horror when an unopened bud adhered itself to my shirt sleeve, then detached itself from its mother and left this world an uncorrupted virgin. I suppose that's what you could call coming to a sticky end. My clumsy fumblings were certainly counterproductive in this instance.
Mauka's glamour-puss cousin, Mirabilis jalapa, the Marvel of Peru, has big colourful, fragrant flowers, which featured in pioneering studies on Mendelian inheritance of flower colour in the early 1900s. It also took a leading role in the first conclusive case of cytoplasmic inheritance, where genes outside the nucleus were shown to affect the plant's possession (or not) of variegated leaves. The genus Mirabilis as a whole are also known as the four o'clock flowers, this being the time in the afternoon at which they usually open and begin releasing their heady fragrance. The apparent cause is the decline in air temperature as the sun's rays weaken, rather than any direct association with a particular hour of the day.
Mauka, by contrast, seems to be a bit of a shrinking violet, with small flowers and I've yet to catch them in fragrante delicto. On my windowsill, the flowers seem to open at night, followed by closure early the following morning. Could it be that four o'clock actually refers to 4am rather than 4pm? I'm not sure if I can face staying up into the wee hours, headtorch, tweezers and paintbrush in hand in the hope of effecting a successful pollination. I need my beauty sleep.
Many species of Mirabilis are facultative outcrossers, that's to say they prefer to cross-pollinate, but are able to self-fertilise if a better pollen source isn't forthcoming, or if the moths which usually pollinate them are prevented from flying by low temperatures. It will be interesting to see whether this is also true in mauka's case. I'll be looking out for swelling anthocarps, the distinctive dry fruits which are characteristic of the family Nyctaginaceae to which Mirabilis and Bougainvillea belong.
The case for inducing flowering in mauka by daylength manipulation grows ever stronger. Let's hope I'm man enough to remove and replace light excluding covers over a few plants for a few weeks this summer in the hope of tricking them into flowering. Then I can let the moths do the rest.