Nasturtium is my favorite cultivated flower. Easy going, tasty, beautiful, and fast growing. I use the leaves in sandwiches and pesto.
The leaves are entire, peltate, smooth with L-O-N-G petioles that attach to the middle of each leaf. The petioles and stems are almost juicy/succulent.
The showy, single flowers have five petals, 3 of which are hairy at the bottom (called clawed) and two of which are not. The literature describes 5 sepals, one of which is altered to become a spur which contains the reproductive parts, but in my samples, I found 5 sepals PLUS the spur. The ovary is superior and small, with 8 stamens that look different in size and shape at this stage of development, see photo.Looks like vertical dehiscence. The one style is small. See it as the whiter element to the left side of the leaf, attached to one of the stamens. When I cut into the ovary, I could not see anything useful (at 3:00 and 5:00 on the leaf), but it is reported to have 3 carpels. The seed looks like a wrinkled little walnut that breaks easily into three parts, so 3 carpels make sense.
Well done, I love nasturtiums too! They grow so easily from seed and are very tasty and make for a great decoration of cakes or fresh salads. The cultivated Trapeolum is of hybrid origin, so in those hybrids the number of petals and sepals sometimes can go array a bit from what we normally expect.