science – Page 2 – My Chicago Botanic Garden

A Rare Plant Portrait: The Silverleaf Sunray (Enceliopsis argophylla)

Project Overview:
Shannon Still and Nick Jensen work on a project studying the impact of climate change on the distribution of rare plants in the western United States. The grant, funded through the Bureau of Land Management (BLM), examines the changes in projected species distributions between now and 2080. The goal of the research is to help BLM to make informed management decisions regarding rare plants. The research takes them to many exciting destinations as they search for rare plants in the west.

habit of Enceliopsis argophylla — Habitat of *Enceliopsis argophylla*, which thrives in gypsum-rich soil.

The silverleaf sunray (Enceliopsis argophylla), is a photogenic species in the Asteraceae, or sunflower, family. This rare plant grows in basal clumps of silver-colored, hairy leaves with flowers extended on long stalks, and the entire plant may reach 2 feet tall. The flowers nod with maturity.

The large yellow daisy flowers are 3 to 4 inches across when open. They are quite a sight and stand in stark contrast to the habitat. Due to the extreme habitat, silverleaf sunray offers one of the more striking photo opportunities as the plants grow from a barren landscape.

Silverleaf sunray on a barren hillside. — Silverleaf sunray on a barren hillside

Nick Jensen with a silverleaf sunray. — Nick Jensen with a silverleaf sunray

These gems are found in Clark County, Nevada, east of Las Vegas in the Lake Mead area. They are also found in Mohave County, Arizona, close to Lake Mead.

The habitat for the silverleaf sunray has been encroached by Lake Mead and is threatened by off-highway vehicle use to a minor extent. The habitat in which the sunray grows is easily damaged due to the fragile soil environment (see photos to left) in which the species lives. Much like the dwarf bear-poppy (Arctomecon humilis), the silverleaf sunray grows in a gypsum-rich soil that typically has a healthy soil crust. Damage to this crust can allow invasive plants to grow more easily.

The Bureau of Land Management lists the silverleaf sunray as a sensitive species in Nevada and the species was considered, but rejected, for protection under the Endangered Species Act. Around Lake Mead the silverleaf sunray grows with the golden bear-claw poppy or Las Vegas bear-poppy (Arctomecon californica), a federally listed species. So while the species is not federally listed, the habitat is often protected due to the proximity of other federally listed rare plants.

Silverleaf sunray is a striking plant that grows in close proximity to urban and recreation areas. If you are ever in the Las Vegas area, it is worth traveling the short distance to see these plants.

How to Train Your Plant

Since it’s winter, and we’re all stuck looking at leafless plants outside, why not try growing some plants indoors? Better still, why not experiment with your plants to understand them better?

In this activity, you will confuse a bean sprout and train it to grow in any direction you want. Sound like fun?

You will need:

a gallon-size zip-top bag
paper towels, preferably 2-ply (if they are single-ply, double them)
a pinto, lima, or kidney bean (try whatever you have) soaked in water overnight
a stapler
water
tape

Lay the paper towel flat inside the plastic bag. If it doesn’t fit exactly, fold the edge of the paper towel.

Put a staple in the middle of the bag, and place the bean just over the staple. Add two staples that are separated by more than the length of the bean.

The staples hold the bean in place, but should give enough room for the bean to grow between the staples. Watch to see how the bean grows and needs the space. Add just enough water to the bag to wet the paper towel. Take care not to have a pool of excess water in the bag.

Now tape the bag to a wall, or your refrigerator, or a window if it’s not cold. That’s right, put it right on a vertical surface. Don’t close the bag, because it’s good to allow water and air to move in and out. The picture shows you what it should look like. (Ignore the four staples, only put three on yours. I discovered that four staples trap the seed and ruin the activity.)

As soon as your plant has grown a root and a stem that is 1-2 inches long, turn the bag one quarter turn and put it back. You may have to wait a week – less if your bean is warm, more if your bean is in a cooler location, like my office.

This is what it may look like at this stage after I turned it.

Now wait. When the sprout has grown another inch or so, turn the bag again in the same direction. Since the opening of your bag will now be on the bottom, you should seal it. Then wait.

Yes, I know, you have to wait a while to get results. The timing will depend on the level of light and the temperature. That’s the way it goes with growing plants. Horticulturists – the people who grow plants – are some of the most patient people you will ever meet!

Here are the results of one bag I started in early January, about three weeks ago. Since I turned the bag clockwise, the roots and stem appear to be going around counter-clockwise.

From here on it’s up to you. Let the plant grow and turn the bag when you want to change the direction of growth, let it go for as long as you like. Can you make it grow in a full circle around the middle of the bag?

What is Going On Here?

Plants are affected by the gravitational pull of the earth. When you turn the bag, you change the direction of the force and the plant responds by changing direction of growth. This phenomenon is called geotropism. A tropism describes an organism’s response to a stimulus. In this case, the “geo” refers to the Earth, and it is the scientific way of saying that the earth makes leaves grow up and roots grow down. This phenomenon may also be called gravitropism.

The Garden’s horticulturists play with gravitropism. Look at this picture of the Visitor Center bridge in fall. Notice the gorgeous pink mums hanging from the trellis.

Left alone, the stems of these plants would naturally grow up like the mums planted on the sides of the bridge. Our horticulturists train the stems to grow down, cascading over the sides of their container, by tying small weights on the stems while the plants are growing in the greenhouses. They actually use metal nuts from a hardware store! The weights are removed before the planters go on display, and they look fabulous, thanks to the horticulturists’ success in playing with the plant’s response to gravity.

A Rare Plant Portrait: The Dwarf Bear-Poppy (Arctomecon humilis)

The genus Arctomecon (also known as bear-poppy), contains three beautiful species restricted to southwestern North America. In this exceptional genus, dwarf bear-poppy (Arctomecon humilis) is the rarest — and perhaps most remarkable — species, due to its profusion of delicate white flowers and unique habitat.

In many ways, the dwarf bear-poppy is a poster child for rare plant conservation. It is restricted to a small area in southwestern Utah close to the Arizona border, near the city of St. George. A stunning plant, it grows in a notably hostile habitat — it is not uncommon to find this species growing completely alone on gypsum soils on steep, exposed hillsides and ridges.

PHOTO: The three 'claws' at the end of each leaf of the bear-poppy. — The “claws” at the end of each leaf

Dwarf bear-poppy is topped by a mass of white flowers in late April and early May that often cover the entire plant. Each flower consists of four delicate, white petals surrounding myriad yellow stamens, all of which sit atop a plump green, round ovary. Unopened, graceful, green flower buds droop, waiting to open. When looking out over this landscape, backlit plants in full bloom seem to glow in the early morning or late afternoon light.

A close inspection of dwarf bear-poppy’s hairy leaves with their three “claw-tipped” teeth at their apex sheds light on the origin of bear-poppy as a common name for these plants. Everything about dwarf bear-poppy exudes beauty.

Delicate flowers of the Dwarf bear-poppy. — Delicate flowers of the dwarf bear-poppy

It is found in approximately ten locations in Washington County, Utah, and is listed as an endangered species by the U.S. Fish and Wildlife Service. Dwarf bear-poppy is threatened by development, mining, and off-highway vehicle (OHV) damage to its habitat. The dwarf bear-poppy grows in soil that forms a thick, crunchy, structurally-complex biological soil crust that is rich in gypsum. The habitat is easily damaged by hiking, grazing, and OHV use and is slow to recover.

PHOTO: OHV damage to the habitat. — OHV damage to the habitat

The habitat for the dwarf bear-poppy in the photo shown below has not had OHV activity for at least seven years (and likely longer) and still shows signs of heavy damage. In fact, full recovery of a soil crust can take up to 250 years, so a little damage can have long-lasting impacts. Therefore, conservation efforts have included fencing as well as the establishment of nature preserves, managed by The Nature Conservancy, to prevent further OHV damage.

Dwarf bear-poppy is a strikingly-beautiful, rare, and threatened species. Conservation and restoration efforts should ensure that it continues to be a botanical treasure for future generations to cherish.

Habitat range for Arctomecon humilis, the Dwarf bear-poppy.

Play with Your Pine Cones

I was walking under some pine trees near the Learning Campus and I took a picture of the cones I found.

PHOTO: The ground under the pine tree is covered in dry, brown pine needles and cones that are open, closed and in between. — I found two different kinds of cones on the ground under the pine tree.

When I was young, I noticed there were two different kinds of cones — some solid cones like the three in the lower left corner of the picture, and others are more like the open, branched cones at the top. I thought the pine tree made two different kinds of cones. Actually, they are different forms of the same kind of cone. I will show you how this happens.

I took three cones that were the same size and shape. Then I soaked one cone in a bowl of water.

PHOTO: Pictured here are three pine cones of similar size, shape, and color. — I started with three pine cones of the same kind, shape, and size.

PHOTO: One pine cone is floating in a white bowl full of water while the other two are resting on the right side of the bowl. — I placed one cone in a bowl of water. It slowly began to change.

PHOTO: One pine cone is in the white bowl, now almost fully closed after ten minutes, while the other two are dry and unchanged at the side. — After about ten minutes, the wet pine cone is almost completely closed, while the dry cones are still open.

PHOTO: A wet, closed cone is shown next to a dry open cone. — Wet cones are closed, dry cones are open, and that is why cones from the same tree come in different shapes.

Then I let the wet and dry cones sit on my desk overnight. Guess what happened. Try it yourself to get the answer! Go outside and find a pine, spruce, or other conifer tree. Bring pine cones from those trees inside and watch them over time as they adjust to the warm, dry conditions in your home. Put one in bowl of water and see what happens. Let it dry and see if it changes again.

What is going on here?

Pine, spruce, Douglas-fir and other conifers are so named because they produce cones that bear their seed. When conditions are favorable for the seeds to fall and grow, the cones open and release them. The seeds have the best chance to survive when the air is dry and windy, so they can blow to a nice fertile spot away from the shade of the mother tree. When conditions are wet and not so good for a traveling seed, the cones close to protect them.

Though the cones I found under the tree had released their seeds a long time ago, they still responded to the moisture levels of the ground and air. These cones were in between being damp from the rain over the weekend and drying in the sun.

Pine cone history

By the way, all conifers belong to a group of plants called gymnosperms. This means they produce “naked seeds” — seeds that are not contained within a fruit. Conifers do not grow flowers. Before there were dinosaurs on the planet, all plants reproduced by either spores or naked seeds. The seeds of some conifers can take up to three years to mature. Flowering plants (angiosperms) have a much more rapid reproductive cycle. Some angiosperms flower and produce mature seed in just one week. Understanding how cones and flowers have evolved is what Dr. Pat Herendeen is trying to figure out from plant fossils.

Camp CBG Registration is Open

Summer camp seems far away, but Camp CBG registration is open early this year. Discover what makes these camps unique, with 75% of the time spent outdoors learning about the natural world. New this year are two-week camps for 6-9 year olds. Learn more at http://www.chicagobotanic.org/camp/summercamp.