Catkins: Spring’s Botanical Wonder

Sneezing, coughing, watery eyes – everyone is complaining about allergies this time of year, the Arboretum staff included. Many people point the blame at any pretty flower they see in early spring, such as Bradford Pear blossoms (Pyrus sp.), redbuds (Cercis sp.) or daffodils (Narcissus sp.). But it is likely to be less obvious blooms causing your sniffles – catkins. The trees are chalk full of these inconspicuous, pollen-spraying fiends! I’ll have to put aside my animosity for them and their disastrous effect on my sinuses while I explain their fascinating botany…but I’ll have to blow my nose first.

Catkins

Catkins at the Arboretum now! From left to right, willow (Salix), alder (Alnus) and aspen (Populus)

Structure and Function

Catkins are flowers adapted to be pollinated by wind, which is known as anemochory. (Pollinated in water? Hydrocory. Pollinated by birds? Ornithochory. You get the idea.) Their dangling habit is part of this adaptation, and pollen is released from male flowers when wind causes them to shake. These worm-like blooms are actually hundreds of tiny flowers strung together.  Each catkin is either male or female, but both sexes may or may not be carried on the same plant. If a single plant produces both male and female catkins it is considered ‘monoecious’. Some tree and shrub species have separate sexes and produce only male or female flowers on a single plant, meaning they are ‘dioecious’.

Salix caprea flower stages – male catkin (I) and female catkin (III), ovary cross section (V)

No Beauty Queen

In general, the prettier the flower the less likely it is to be pollinated by wind. The striking white pear trees blooming now are mostly pollinated by bees, and therefore not the cause of wind-born pollen allergies. If the flower is colorful and attractive it is probably luring in winged creatures to carry it’s pollen becuase the grains are too heavy to be carried on the wind. Catkins are not burdened with the task of being beautiful – they don’t have to attract a subjective eye for pollination. But in the plant world, if you can’t be pretty then you must be prolific! These little flowers release enormous amounts of pollen onto the breeze, with little chance that any of it will serendipitously land on the female of the corresponding species. Not only does the pollen grain have to float its way to the opposite sex, but it must then land exactly on the tiny stigma, the pollen receptacle atop the female flower, to produce pollination. What a feat! With such slim odds, it is no wonder that these trees produce prodigious amounts of pollen, much to the dismay of allergy sufferers.

Left , ragweed pollen (Amrbosia) Right, Hazel pollen (Corylus). Hazel trees produce catkins. Ragweed does not, but the pollen is so annoying I thought everyone should know what it looks like.

Left , ragweed pollen (Amrbosia) Right, Hazel pollen (Corylus). Hazel trees produce catkins. Ragweed does not have catkins, but the pollen is so annoying I thought everyone should know what it looks like.

 

Whether their pollen ends up in your nose and eyes, or the catkins themselves fall wet and soggy on your windshield, try not to loathe them too much – they are just another of nature’s incredibly well-designed survival mechanisms, and all your sneezing is just a sign that spring has arrived!

 

Attributions:
Wikimedia public domain images
Salix flowers – By Internet Archive Book Images [No restrictions], via Wikimedia Commons
https://archive.org/stream/textbookofstruct00thom/textbookofstruct00thom#page/376/mode/1up

Ambrosia pollen – By Nikita Karasik (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Corylus pollen – By Doc. RNDr. Josef Reischig, CSc. (Author’s archive) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Ragweed: An Annual Affliction

Achoo!

A couple of weeks ago, my son and I started to experience the annoyance of head, nasal, and throat responses to extra pollen in the air. I did some investigating of roadsides and sure enough, the ragweed was just starting to bloom and reported pollen counts were spiking. Kansans have really enjoyed relatively cooler temperatures and ample rainfall this summer. Our landscapes have been green and our gardens have been productive. With the good comes the bad…mosquitoes and ticks have been abundant and we should expect a monster ragweed season through the rest of August and September.

Plants with annual life cycles (as opposed to perennials or biennials) are the most productive airborne pollen sources this time of the year. Annuals complete their whole life cycle of germination, rapid growth, profuse flowering (the culprit in this story), voluminous seed production, and death in one growing season. Three of the the worst annual plant offenders for airborne pollen production this time of the year include common ragweed, giant ragweed, and sumpweed.

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Wind-pollinated common ragweed (Ambrosia artemisiifolia).

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Wind-pollinated giant ragweed (Ambrosia trifida).

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Wind-pollinated annual sumpweed (Iva annua).

While ragweed season is the worst for me, I do often notice airborne pollen spikes of flowering elms and maples in early spring, cedars and wheat crops late spring, and sometimes even warm season prairie grasses in mid summer.

All flowering plants produce pollen, but wind-pollinated plants produce smaller, lighter pollen that use wind to migrate from male to female flowers…and unfortunately our nasal passages. Wind-pollinated flowers do not need to invest energy in expensive color (and nectar) to attract insects to move pollen, so their flowering often goes undetected by the human eye. A common misconception is that colorful, perennial flowering plants, including goldenrods and sunflowers blooming this time of the year, are causing us to sneeze. However, their flowers have heavier pollen, which are not carried in the wind, and which require an insect with a hairy body/legs to migrate to other flowers. Flowers with colorful petals are not our allergy nemesis.

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Insect-pollinated Missouri goldenrod (Solidago missouriensis) does not cause allergies.

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Insect-pollinated compass plant (Silphium laciniatum) and wind-pollinated giant ragweed.

Annuals including ragweed require disturbed, open soil to thrive. Although their pollen affects me, I am glad for the ecological role that annuals play in quickly establishing disturbed soil and minimizing erosion until long-lived perennials can establish and take their place. Most of our soil at Dyck Arboretum is tied up and covered with perennial native plants, and I actually had a hard time finding examples of annuals to photograph.

I’ll finish on one more positive note. Grains including corn, wheat, rice, oats, rye, barley, and others are all wind-pollinated plants too. I guess we should be thankful for the wonderful world of plants and what their sometimes annoying pollination mechanisms have to offer.

So, grab the tissues, nasal sprays, antihistamines and suffer through.