Flowers and Sex

No, not the “flowers as symbols of love” trope.

Flowers are quite literally the sex organs of plants. A complete flower has male parts (stamens) and female parts (pistils.) In the daylily photo the stamens are the thin stalks (filaments) ending in the fluffy-looking things (anthers), while the part of the pistil visible is the slightly curved stalk below them.

The anthers release pollen (analogous to sperm cells in animals) which, when if falls on the sticky end of the pistil (the stigma) grows a tube to the ovaries, fertilizing the ovules within it, which can then grow into seeds. Those notorious birds and bees often assist in the process by transporting the pollen from one flower to another. In fact the colors and smells of flowers probably evolved to lure these pollinators, as did the nectar our honeybees make into honey.

The ovary, which can be above or below the base of the petals, is what grows into the fruit—the sometimes-edible part surrounding the seeds. As it happens, the ovary in the daylily is above the petal base and hidden by the petals; that on the squash we’ll discuss later is below the petal base.

Female zucchini flower, showing small squash as stem. Male flower stem visible in background.

Now plant sex is a good deal more varied than animal sex. Some plants have both stamens and pistil in the same flower, like the daylily. In extreme cases, the flower doesn’t even open, and the plant pollinates itself, but this is rare and seen mostly in some members of the legume and viola families. At the other extreme, the whole plant is male or female, and two plants are needed for pollination. Some plants cannot be fertilized by their own pollen, and two varieties must be planted in order for them to set fruit. And in some there are two distinct kinds of flower, male and female, on the same plant. The male flower has stamens and produces pollen, but never produces seed or fruit. The female flower is the only one that produces the fruit.

If you’ve been reading this blog, you’ve no doubt noticed that I’ve been referring to male and female squash flowers. I grow zucchini, and they produce male flowers first, and then female flowers. Only the female flowers actually produce squash, so those are the ones I watch for.

How do I tell? Well, I could look inside the flowers, which are large enough to see the difference. But with zucchini, there’s a simpler way. In squash, the ovary is below the base of the petals, which means that if you look at the “stem” of a female flower, most of what you see is what will grow into a squash. Slender, smooth stems indicate male flowers (lots of those right now) which will never produce squash themselves. Fat stems, or yellow ones in the case of yellow zucchini, indicate female flowers and squash to come.

I don’t think the squash pictured will be ready to eat before next week, though they can grow remarkably fast from this size – the photo was taken June 28. But I fully expect to have my first zucchini by the end of next week. (I’d better remember to add parmesan cheese to the grocery list, as I prefer zucchini braised in olive oil with oregano and sprinkled with cheese and garlic salt.)