Blooming Petioles!?!?

If you look at most plants, the stalk that supports the flowers (peduncle) emerges from somewhere on the stem. Sometimes the flowers grows at the end of the stems and other times them develop along the stem, particularly at the place where the petiole of the leaves (the stalk that supports the leaf) meets the stem.

Streptocarpus

Streptocarpus

Since this is the norm, I was surprised when I was looking at the streptocarpus hybrids that I have growing in the house. The plants have started to come into full bloom but where those blooms develop surprised me.

Streptocarpus hybrids leaves grow in a rosette. Instead of large spaces between the leaves (internodes) like tomatoes or peas, in plants with a rosette growth pattern, the internodes are very short. This cause the plants to grow their leaves in a tight circular pattern. Some plants that have this rosette form of growth are dandelions, agave and african violets. In these plants the flowers still emerge from the stem, short and compact as it might be.

That’s why I was so amazed with where the flowers develop on a streptocarpus. Instead of developing from the stem, in this plant the flowers develop along the base of the petiole. Usually there are two or three inflorescences that grow from each petiole, the first emerging closest to the stem and the subsequent ones developing further along the petiole away from the stem.

strepflower copy

As one who’s always looking closely at where and how the various parts of a plant grow, this is something I’ve never seen before. I’m sure there are other plants whose flowers grow from the petiole but I don’t know of any other than the streptocarpus.

This is just one more example of the amazing variety of plant morphology. Who knows what the evolutionary advantage is in having blooming petioles? All I know is that streptocarpus hybrids have them and it’s a difference from other plants that’s pretty cool!

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