Smut in the Garden-Blog 39 in a Gardening Series

A version of this column first ran in the Roane County (WV) Reporter and Times Record as part of a gardening series. Support local journalism! Subscribe to your local newspaper. This is one of a series of blogs for new gardeners. Start reading the whole series here: Part 1. 

There is a fungus that attacks corn, called corn smut, which erupts from an ear or stalk as a solid gob in dark grey and white. I saw it once in my garden, years ago. But this column is not about that fungus. It’s about plant sex.

Just like animals, most plants rely on sex to keep their genes mixing and matching, to give selection a field to operate on. There are some species that just pass on their genes to daughter plants, unchanged—and gardeners often arrange for such a transfer, through grafting, cloning and the planting of tubers (and bulbs and rhizomes and corms, not that I can tell the difference reliably). They do this so they can grow a specific variety they prefer, and not some variant that comes about through the mixing of genes.

But if we’re looking at seeds, then there is the male element—pollen—and the female element, the egg cell, which is inside the ovary—generally there is just one ovary in the heart of the flower. But here’s where it gets interesting because plants get into the LGBTQIA+ thing in a big way. Some flowers are “perfect”—this mean the flower has male and female parts, and can pollinate itself, or be pollinated by another flower of the same kind. But in other plants, there are separate male and female flowers—and if the species is dioecious, each individual is either male or female. Persimmons and hollies are examples. You have to have individual trees of both genders to get fruit (berries). But one male holly or persimmon can pollinate several females—like one rooster fertilizing several hens. Red maples are also dioecious—the females are a more lurid red than the duller males (and I leave it up to you to make the jokes in response to this information).

Most plants, I think, are monoecious. This means that male and female flowers occur on the same plant. So it can be self-fertilized, or it can fertilize and be fertilized by, another plant. The latter is desirable for purposes of genetic mixing, and sometimes this is accomplished, to some degree, by having the male flowers come first, overlapping the females. I think the idea is that individuals vary slightly in their timing, so this way an early plant may have its pollen go to waste, but its female flowers will be pollinated by a slightly later plant’s pollen. A late plant may not be fertilized but its pollen does carry on fertilization of female flowers. One example you can see in the garden is among squash, which generally make several male flowers first, before producing the first female flower (the females are easily recognized because they have a tiny fruit already forming at the back of the flower).

And in fact I’ve read that it can get more complicated than that—some plants are mostly male or female but can change under certain conditions. An interesting example is Jack in the Pulpit. Young or undernourished plants won’t bloom at all. More sizable plants will put up entirely or mostly male flowers. But a robust plant will make female flowers within that interesting spadix (the “pulpit”), followed by the red berries. In looking up the details, however, I found out there are some animals that do this too.

Plants have another wrinkle not seen in the animal kingdom—since they can’t travel in search of mates, their pollen does so while the plant remains rooted. In some cases they rely on wind to accomplish the transfer. Grasses are wind pollinated, including grains–notably, the one most likely to be in your garden, corn. This is why corn must be planted in blocks, not a long single row. The pollen falls from the anthers on top down to the corn silks, and outside rows get less pollination.  

But a good many plants rely on us animals to act as a dating service—especially bees. Not just honeybees, which have become scarcer in recent years, but also many native species of bees are important pollinators. Some moths, butterflies and even birds also pollinate plants. What the pollinators get out of it is the nectar; while collecting that they brush up against the pollen and transfer some from one plant to the next. For this reason, plants that depend on pollinators have big, colorful, often fragrant flowers (no, it’s not for us, silly) while wind pollinated plants generally have boring, inconspicuous flowers. I’ve read that a dearth of pollinators in China led to humans acting as pollenizers, which seems inconceivable—imagine dusting all of many thousands, or tens of thousands, of blooms on just one apple tree. No, let’s keep the bees! Let’s stop spraying insecticide.

Similarly, the fruits of many plants are large, conspicuous and sweet if the plant depends on animals to carry it off to spread the seed. But other seeds spring from a pod that bursts when it’s ready, or roll off downhill, get carried away by water, float away on the wind, or attach themselves to fur to have an animal carry them to a new location. I read once that humans are implicated in the development and spread of mangoes, and maybe avocadoes—because who else is capable of weaving baskets in which to carry such large, but delectable fruits? Then we planted the seeds, deliberately or accidentally, and started new colonies of the trees. This was probably in Michael Pollan’s Botany of Desire (all his books are fascinating).

Read the rest: Part 1. Part 2. Part 3. Part 4. Part 5. Part 6. Part 7. Part 8. Part 9. Part 10. Part 11. Part 12. Part 13. Part 14. Part 15. Part 16. Part 17. Part 18. Part 19. Part 20. Part 21. Part 22. Part 23. Part 24. Part 25. Part 26. Part 27. Part 28. Part 29. Part 30. Part 31. Part 32. Part 33. Part 34. Part 35. Part 36. Part 37. Part 38.