Friesner Herbarium Blog about Indiana Plants

Hemlock on the Butler University campus

Hemlock (Tsuga canadensis ) is one of fewer than a dozen conifers, cone-bearing trees, native to Indiana.  It is called a glacial relict because it first grew in the state at the time following the retreat of the last glaciers, around 10,000 years ago.  As the great ice sheets that at one time over the northern 2/3 of the state melted, vegetation reclaimed the land.  Initially, the climate was cool and wet, similar to the boreal forest climate of today.  As the glaciers left, the climate gradually became warmer and drier.  Hoosier hemlocks could only grow and reproduce in our wettest and coolest remaining habitat, the mostly northward-facing slopes of deep cut ravines and steep rocky bluffs along streams and rivers.  Think of Turkey Run and Shades Stare Parks.  Populations of hemlock have persisted there for thousands of years!

Hemlocks can be distinguished by their soft short needles, with two fine parallel white stripes on the under surface, and by their very cute, less than 1 inch long cones.  Needles are borne singly (not in clusters like pines) in two rows on the twig.  The very top of a hemlock tree often bends over like a flag.

Hemlock twig with cones

Hemlocks are used a lot in landscaping as an evergreen ornamental in Indianapolis.  As far as we know, all hemlocks in Marion County have been planted.

This hemlock is a tree of the northern forest immortalized in the poem ‘Hiawatha’ by Longfellow and of the Appalachian Mountains, not the plant that killed Socrates.  That hemlock, as I understand it, was poison- hemlock (Conium maculatum), a member of the carrot family native to Europe and a non-woody plant.  Is does grow wild in Indiana as an introduced species.

Sycamores along the canal behind the Butler campus -click to enlarge

Sycamores (Platanus occidentalis) are signature trees along Indiana’s creeks and streams. This time of year is a great time to see them from bridges as you drive over. Their white mottled bark stands out against the mostly gray of the other trees.

Distinctive sycamore bark

Biologists don’t know why there are so many different patterns to tree bark. One idea I read recently suggested that bark that peels off easily may make it hard for vine to climb up trunks.

Sycamore leaves and fruits (= round balls hanging from branches)

Sycamores have seeds borne in fruits that look like Sweetgum (Liquidambar styraciflua), without the annoying woody capsule. They have the same shapes fruits, globes, that hang from stalks below the branches. They are soft and fall apart. You won’t twist your ankle on them. Seeds have tufts of hairs attached to help them spread in the wind to your gutters, window screens and other places.

This large tree is in the backyard of our house near the Butler University campus. It is as tall as a 4 story building and gives us great shade. It also produces huge, tough leaves, loses chunks of bark when it is dry in the summer and then again when it rains as the trunk shrinks and expands.

Large sycamore near Butler University

Every spring we lose at least one flush of leaves as the tree gets infected by anthracnose, a fungal infection. Anthracnose thrives during moist cool springs. Sycamore is one of the last trees to leave out in Central Indiana, maybe to try to avoid the fungus.

 

View from my office window in Gallahue Hall, Butler University on 11/9

An estimated 30% of wild plants, those growing outside of cultivation, in Central Indiana are not native to Indiana.  To a botanist or ecologist, a native plant in Indiana is one that was here when European settlers came.  We should value and protect native plants, in part, because they are the best resource to be the base of the food web that supports all of our desirable wildlife, from butterflies to birds to mammals. 

Asian bush honeysuckle

The pioneers brought many plants, intentionally and unintentionally, that evolved in Europe but now grow wild here.  The last 200+ years has seen the introduction of many more plants from all over the world.  Just a few of these species are so successful here that they are now threats to biodiversity in natural areas – they crowd out native plants in woods, wetlands, and prairies.  This had led to the moniker of   “invasive species.”   

 This is a good time to appreciate the ubiquitousness of a few invasive species in and around Indianapolis.  If a tree or shrub has green leaves still on it in November, it is most likely non-native. 

White mullberry

Right now, scattered throughout our remnant woodlands and along fence-rows while you are driving, you can easily see Asian bush honeysuckle, White mulberry and Norway maple.  Part of the key to their success here is that they stay green longer than natives and often leaf out earlier, effectively beating the natives to the all-important resource of sunlight. 

Norway maple

Ginkgos, with their distinct leaf shape, were first known from the fossil record.  They date back to the Jurassic, the time of the dinosaurs.  They were rediscovered growing in remote mountain forests in China.  They have been cultivated for centuries in Buddhist temple grounds.  All our trees were derived from this seed stock.

 Ginkgo is unusual in that it has separate sexes, male and female trees, and that the difference is due to chromosomal differences.  Male trees are usually planted because the “fruit” of the female is stinky when it falls to the ground.  I’ve heard it referred to as smelling like rancid butter.  Where I saw “fruits” on the ground yesterday, if they had been stepped on, they smelled just like dog poop.  Despite that unappealing notion, younger fruits are a component of Asian cuisine.  I’ve seen cans of them in local markets.

The Latin name is Ginkgo biloba.  The leaves are often notched into two lobes.  The iconic leaf shape is a motif often used in jewelry.

This tree is the source of the supposed memory enhancing herbal treatment of the same name.  From what I have read, it has shown some promise in delaying cognitive decline in folks with Alzheimer’s Disease but there is no evidence with will help college students cram for finals or me to find my car keys.