Tiny seeds and how to grow them
There are few times when I have tried to collect seeds and been completely confounded so as to what exactly what I'm meant to be collecting. One such case is the tropical tree Mitragyna parvifolia, or the Indian burflower-tree. The see produces beautiful globose inflorescences (flower clusters), which are pollinated by many species of insect pollinators in nature. Once successfully pollinated, the trees produce a similarly globose infructescence (or fruit cluster) - a multi-lobed, woody sphere, around 1-2 centimetres in diameter. Each lobe (a single cluster consists of around 200-250) consists of a tiny elongated fruit, not more than 4 millimetres long. Much like a bewildering botanical version of Russian dolls, each tiny fruit further dehisces lengthwise, and contains two, nearly microscopic, winged seeds.
Each of these seeds (no more than 2 mm long) is so insignificant that while manually breaking apart the fruit, it could easily pass for a piece of chaff. To give you an idea of scale, these seeds are so small, that around 9,000 seeds weigh a single gram, and can fit onto a teaspoon!
So how exactly does one germinate such minute seeds? Mitragyna is not, by far, unique in the size of its seeds. Many species of cacti, succulents such as Lithops, and Begonias have dust-like seeds, but these are, almost always small, herbaceous plants. Mitragyna on the other hand, is a tropical forest tree which easily reaches heights of 25 metres. in the past, making the size of its seeds an evolutionary and ecological anomaly.
In the past, I have had a fairly poor track record with these seeds. For starters, its almost impossible to separate seeds from chaff, so I tend to prefer to sow in sterilised compost (hot water works well, like you would use for fern spores) to prevent disease in the early stages of growth. A relatively dense seeding of the container with seeds, and a very light cover of sieved vermiculite makes sure that the seeds don't get smothered and have enough light and air. After a light misting I then cover the containers with a layer of cling film until I see signs of growth. Germination can take upto 3 weeks, and the rate is sporadic, so patience and a keen eye is key.
Sometimes plants can throw us a curve ball when it comes to germination, maintenance or other aspects of their culture. I always find that trial and error - and constantly learning from those errors and making adjustments in the techniques used - is the best way to proceed. For hints from nature, look up the natural history of the plant, and how it would grow and germinate in its natural habitat. What are some of the smallest seeds you have encountered or grown? How did you germinate them? I would love to hear your experiences below!