28 October 2015

The other day I was eating a yam and wondered where the name “yam” came from.  The Oxford English Dictionary said the word is from West Africa and it’s not the name of the plant I was eating.

True yams are in Dioscoreaceae, the Yam family. Native to Africa and Asia, they’re an important food staple with many cultivated varieties. Our yams were named by African slaves who saw the resemblance to the yams back home.  A true yam (African type) looks like this.

North America has native members of the Yam family but we don’t find them in the grocery store.  Wild yamroot (Dioscorea villosa) is common in western Pennsylvania and is most noticeable in spring when its pleated leaves grow in a whorl near the ground.

The “yams” we eat are sweet potatoes (Ipomoea batatas), members of the morning glory family, Convolvulaceae.   Their flowers show what family they’re in.

Unfortunately sweet potatoes are labeled Yams in the grocery store because of USDA rules that say:  Sweet potatoes that are white inside = “sweet potato,” orange inside = “yam.”  I must look for the word “yam” to find an orange sweet potato in the grocery store.

I have never seen a white-inside sweet potato. Have you?

Read more here at the Huffington Post: What’s the difference between sweet potatoes and yams?

(photos from Wikimedia Commons.  Click on the images to see the originals)

Though these look like leaves, they aren’t.  They’re liverwort, a plant related to moss that often grows right next to it.

The flat green ribbons place this plant in the thallose liverwort group.  There are also leafy liverworts that look like moss, some so tiny that they require an expert with a magnifying glass to identify them.

Liverworts (Marchantiophyta) are ancient plants with these amazing characteristics:

• They have no water transport system (i.e. non-vascular). Without internal pipes they’re at water’s mercy to come and go wherever it will. Thus they don’t grow tall.
• They have no protection against water loss so liverworts have evolved the ability to dehydrate and recover in a technique similar to hibernation.
• Liverworts’ cells contain only a single set of chromosomes (haploid). They produce diploid cells only for reproduction.  Animals and most plants are the opposite with double chromosomes in our normal cells and singles only for reproduction.
• Liverworts have no roots.  Instead they have specialized cells on the underside called rhizoids that cling to the surface.  Each cell is holding on!

Look closely and you can see that the “leaf” is a mosaic of plates, each with a dot in the middle.  The dots look like stomata for regulating water loss but they’re actually air pockets.  (Click here for a schematic from the University of British Columbia.)

Liverwort got its name during the Doctrine of Signatures era when people believed that plants that resembled a body part treated diseases of that body part.  Since liverwort resembled animal livers people thought it must be a good treatment for liver disease.  Liver + wort is “liver-plant.”   In reality, liverworts have no medicinal use.

Because they’re at water’s mercy look for liverworts in cool, damp, shady places.  I found these on a north-facing cliff near Breakneck Falls at McConnell’s Mill State Park.

(photos by Kate St. John)

In October these seed pods look like long yellow beans but they’re actually the “fruits” of Indian hemp (Apocynum cannabinum) … or maybe spreading dogbane (Apocynum androsaemifolium).  (See comments below!)

When you see the entire plant they don’t look edible — and they aren’t!  The plant is called “dogbane” because it’s poisonous to dogs and mammals including humans.

During the winter, the pods turn dark brown and crack open to reveal fluff and seeds inside, similar to milkweed.  Click here to see.

Find a spreading dogbane this month and watch the pods change and open over the winter.

p.s. I originally called this plant spreading dogbane because the stems are ‘spreading’ and red but it is probably Indian hemp (Apocynum cannabinum) as you can see from the comments below.  This specimen is on the meadow hillside below the Fern Hollow Nature Center.

(photos by Kate St. John)