Sunflowers need insect visitors to move their pollen around and many bees are happy to oblige! (Image: Brendan McGarry)
Dandelions and their relatives are examples of monoecious plants that have both male and female parts contained within a single flower (though their flowerheads are actually made up of many individual flowers). (Image: Brendan McGarry)
I spend a lot of time outside. I tend the garden, I walk the dog, I nerd out on nature, and I even manage to sit still and relax occasionally.
These are all activities I am grateful to be able to enjoy because I know that not everyone has the same opportunities, nor can they enjoy certain seasons with the same zest.
Unlike a few of my close friends, I don’t have seasonal allergies, and have never had to look at pollen counts or use medications to simply struggle through each day. (Though woe is me, I am fairly certain I am allergic to hops.) According to the CDC, around a quarter of the adults in the US have the seasonal allergy rhinitis or hay fever, which is caused by the body’s reaction to plant pollen – so it’s not unreasonable that those of you reading don’t share my joy right now.
Most plants produce pollen and all pollen is produced for one purpose – to transfer male gametes from one reproductive structure to another, receptive one. You might read this as “I’m allergic to plant sperm,” but that’s not quite accurate. Pollen are gametophytes that generate sperm once they come into contact with an embryo sac – be that on the pistil of a flowering plant or the female cone of a gymnosperm (e.g. conifers). Just like the plants that produce them, pollen is extremely varied, the better to be conveyed by a variety of animals, as well as wind, water, or a mixture of all of the above. (If you really want to get into the weeds, both pollen and the embryo sac can be considered separate organisms from their parents but let’s not complicate things.)
A microscopic view of the pollen grains from a diversity of plants reveals a hallucinatory range of shapes, colors, and textures that help transport them between plants and protect them from getting gobbled up or destroyed by the environment. (Pollen can last for days, where raw sperm would not last hours in most conditions.) Animal pollinated plants tend to have larger, stickier, and more protein rich pollen to cling to pollinators and offer them a reward, while wind pollinated plants tend to have lighter, loftable pollen, (some even have air sacs) to balloon them as far as possible.
A couple weeks ago, Justin (our illustrious leader here at CHS), sent me an unreal looking image of a Georgia skyline filled with pollen. Accompanying this (real) image (from six years ago) were comments blaming the highest pollen count in state history on cities planting only male trees. I am often late to the party on social media happenings (Justin once asked me a question on Twitter and I finally responded a year later and didn’t even realize how tardy I was), but apparently a few years ago the idea of botanical sexism hit TikTok by storm after a single video rested the weight of all pollen allergies on the shoulders of city planners, horticulturalists, and arborists “only planting male trees.” The idea is that these male trees spew forth their pollen everywhere, and with nowhere to go, they just go forth to clog up our bodies with histamines.
Botanical sexism is a term coined by a researcher and horticulturalist named Tom Ogren, who theorized that because of a supposed preferential planting of male plants in landscaping, we are having more societal issues with pollen allergies. At surface value, this sounds pretty reasonable, and it’s true that in some cases, tree varieties bred to not produce fruit or seeds (remember the cherries of last month’s Pikes/Pines) or only clones of male trees get planted in urban spaces. Gingko trees are a good example of this, because female gingkos are almost never planted as street trees or in ornamental gardens because their prodigious fruit production is frankly horrendous, generating rotting piles of inedible fruit that can become health hazards. Continue reading →
