Sinningia piresiana forms a tuber very soon after germination. As can be seen in the picture to the left, the tuber is just about the same diameter as the leaves. The total height of the seedling in the picture, including the tuber, is less than 1 cm [2/5 of an inch].
The difference between the seedling foliage and that of the mature flowering plant is very striking. The seedling petioles are quite long compared to the leaves, while the mature plant's petioles are very short compared to the leaves.
Not all sinningias form tubers quickly. I examined seedlings of Sinningia sceptrum, from seed sown at the same time as the S. piresiana seed. Even though the S. sceptrum seedlings were larger, more than 3 cm [more than 1 inch] tall, they showed no sign of an incipient tuber.
