Why is the Struthiola Striata, Only Fragrant at Night?

July 13, 2015
rangers blog

Driving down our valleys at dawn and dusk you often get a surprise whiff of a very pleasant and sweet aroma that  brings a smile to ones face. This aroma comes from a plant known as the Struthiola striata, and is indigenous to the southwestern and southern cape section of South Africa.

 As can see in the photograph this plant produces very long, pale white, tubular flowers that nearly cover the entire stem of the plant. These flowers are nearly odourless during the day and hardly frequented by bees. This does not seem to be very intelligent, even for a plant considering that pollinators make use of aroma to aid in finding flowers. Adding to the situation is the fact that they have such a narrow tube down the base of the flowers, it’s no wonder why the bees do not frequent these flowers. Bees are simply too big and too robust to fit down the tube to get to the nectar. This begs some questioning. “What pollinator does the Strathiola use?” and “Why are they fragrant only at night times?”

 To answer those questions these plants are in fact intelligent and are an example of species that make use of an effective way of ensuring other flowering plants around them do not  and can not compete with them for the same pollinators. They are an example of a plant species that make use of moths for pollination during the night time. The aroma is in fact a way of attracting moths, their main pollinators. By limiting the aroma to night time and not during the day they are in fact conserving valuable energy and nutrients that would have gone to waste during the day. By producing such an inviting odour during night time they can attract moths from anywhere close by in that region. Moths are dainty, not quite as heavy and robust as bees, and with their thin, long, and highly specialised tongue they can reach down the tube to suck the nectar from the flowers. A brilliant and bold move from  a little plant, to ensure they will survive the harsh life of competition with other plants, ensuring their own survival to the next generation and to simply bring a smile to our faces as we indulge in their aroma during sunrise and sunset.

by Field Guide, Brian Dhori