Tag Archives: odor

Sweetness or Deceit? Attracting Pollinators

28 Sep

Plants are wily, in their own ways. Some beguile with sweetness, others lure with deceit. This weekend at the United States Botanic Garden, I saw examples of both.

The Jamaican Poinsettia (Euphorbia punicea) takes the nicer approach. Below, you can see the brightly colored bracts, which are modified leaves, and a yellow, cup-like flower cluster called a cyathium. Insects are attracted to the clusters by the reddish-pink bracts and are then rewarded with the sugary nectar; in the photo, the glistening drops are almost overflowing from the cups. Arising from the center of the cluster is the pistil (the female reproductive organ), with three curved stigmas at the top, waiting to receive a dusting of pollen from the visiting pollinator.

Successful pollination leads to the development of a seed-bearing fruit. But if the plant has not been successfully pollinated, the fruit may wilt and never produce seeds.

Other plants, such as the Carrion Flower (Stapelia gigantea), attract pollinators by pretending to be (and smell like) something they are not: rotting flesh. You might think that if someone knows a flower smells like a decomposing mammal, s/he would avoid taking a sniff. But no. I partook of the putrid odor more than once, and can confirm that the flower does indeed smell vile. I pointed this out to other passersby, who also conducted repeated olfactory experiments of their own with identical results…. But back to the plant. In addition to its odor, this wrinkly and hairy flower is also meant to look like a decaying, oozing, leathery, peeling dead animal.

And boy, do some insects love that. Perfect spot to lay eggs, with plenty of food for the larvae, or so they think. They are mistaken; their reproductive efforts are futile. But they will have served their purpose: to help ensure the reproduction of the plant by taking and depositing pollen as they go about their business. A devious deception indeed. Here is a close up of the inside of the flower, complete with a green bottle fly circling around, and a pile of ill-fated eggs below.


Spathe and Spadix

9 Jun

There are two plant parts that are frequently found together whose names I quite like: “spathe” and “spadix.” The two words evoke something mysterious, almost like “cloak” and “dagger.” In fact, there is an element of danger when it comes to plants that have both spathes and spadices, such as Anthuriums, Calla Lilies, and the fabulous Titan Arum (also known as the Corpse Flower because it smells like rotting flesh): they are all poisonous. Their sap contains needle-like calcium oxalate crystals, which can cause significant pain and swelling if an unwitting animal happens to take a bite of the plant. Ingesting large amounts can be fatal because the swelling can make swallowing and breathing difficult–but most animals quickly learn to stay far away. The plants have an excellent defense system.

Toxicity aside, plants with spathes and spadices are striking, as evidenced by this Anthurium andreanum ‘Fantasy Love,’ which is a member of the Arum family (Araceae, aka the aroids). This Anthurium may want to repel herbivores, but it also wants to attract pollinators and one way to do that is via the colorful spathe.

The spathe looks like a petal, but it is actually a bract–a modified leaf. It helps get pollinators closer to the actual flowers, which are tiny and are located in spirals on the spadix. Here is a close-up view of an Anthurium spadix–the stigmas on the almost microscopic white female flowers are emitting a fluid that indicates the flowers are ready to be pollinated. If pollination is successful, the spadix will produce little fruits (or berries) containing seeds.

Sometimes spathes are open and fairly flat, as with the Anthurium above, but they can also encase the spadix and appear funnel like, as with Calla lilies. The photo below is an internal view of my neighbor’s ‘Calypso’ Calla lily–with the  deep-red spathe almost entirely surrounding the spadix.

One last fun fact: some spadices in the Arum family can produce a lot of heat in cold weather, reaching temperatures significantly warmer than the surrounding air temperature. The Titan Arum is one of them. This ability is yet another way the plants attract pollinators.  A warm spadix does two things: it provides pollinators with a bit of energy in chilly weather and it acts as a fragrance diffuser, wafting that delicious putrid odor just a bit further as an added enticement. So if you are a pollinator, you get a colorful, warm, and nice smelling (ok, odoriferous) welcome. If you are a herbivore, you come under chemical attack. Isn’t nature great?