Water Wise?

We have spent a lot of time boasting about the native plants on our green roof, and how they're naturally drought-, wind-, and sun-tolerant, so are ideal for this rooftop setting.  I've also mentioned a few times that Laramie is quite arid – we typically receive around 11 inches of precipitation (including water weight in snow!) per year – only 1 inch more than what classifies a place as a desert. 

So what's with the sprinkler?

As much as we'd like to think that we're perfectly mimicking a natural prairie on our green roof, it's obvious we can't do it in every way.  We can't let pronghorn loose on the roof (though that would be sweet!) and we can't set fire to it (oh goodness, can you imagine the ruckus?).  

And we can't recreate all of the benefits that groundwater, soil depth and topography bring to plants in a natural setting. 

Native v. Natural

We need to be careful when we describe the green roof as mimicking a local prairie.  To clarify:  We use native plants.  We don't pretend this is a natural environment.

In a natural prairie, plants have incredible root systems that, depending on the plant, can grown many, many inches, even feet, into the soil to access groundwater and moisture that our 8-12 inches of green roof soil medium can't provide. 

Topography can also play an important role in a short-grass prairie, providing nooks and crannies for plants to grow in, protected from constant wind and sun and benefited by piled snow and rain run-off. 

The green roof is also surrounded by concrete and brick – increased evaporation due to heat island effect is likely a player as well.  And while we're on the topic of evaporation, look at the color of the soil on the roof compared to the native prairies.  We suspect the dark color absorbs more heat from the sun and evaporates moisture more quickly than in prairie soils.

Natural prairie soil

Green roof "soil"

Furthermore, this isn't just a green roof, it's also a showcase garden.  As such, the aesthetics do matter to some extent.  In order for the Berry Prairie to look as beautiful and healthy as possible, we want to give it an extra boost with supplemented water every so often. 

We also have an drip irrigation system set up, which allows for us to soak the roots when the soil dries out.  We can verify whether the soil is saturated, moist or dry through manually trenching or coring the soil, or through the soil probes we have set up throughout the roof.  The probes are set 4 inches below the surface and measure soil temperature and moisture every hour of every day.

Water Usage

With all this said, we try to be really careful to water only what we need to in order to ensure the health of the plants.  We have watered 4 times so far this summer using a sprinkler and the drip system.  It's a manual process, not automated, so if it rains or if it's cool, we don't need to turn on the sprinklers.


What do you think?  Is it right to water our green roof?  How much, how little, how often, and at what cost?

Written by Brenna Marsicek, Biodiversity Institute

Prairie Spotlight: Stonecrop Sedum

Stonecrop sedum (Sedum lanceolatum) is a drought-tolerant, sun-tolerant, wind-tolerant, abuse-tolerant plant that is common found on green roofs for those reasons.  In addition to is toughness, it also has beautiful flowers, shown below.

Stonecrop sedum in bloom on the green roof, June 25, 2013

Note the round, spongy leaves of stonecrop (shown below)—an adaptation for survival in extremely dry environments. In the wild, you may find stonecrop growing in very thin soils on rocks, where the only moisture is from recent precipitation, quickly lost in the hot sun. Stonecrop is a succulent, a plant that holds lots of water in reserve within its own tissues—like a cactus, another succulent. Stonecrop has another adaptation that further enhances its ability to succeed where normal plants would shrivel, which involves its ability to retain its precious water reserve.

The leaves of the Stonecrop sedum

CAM Photosynthesis

All plants must open their stomata (small pores on the leaf surface) to allow CO2 to enter, in order for photosynthesis to occur. But, open stomata also allow water vapor to escape. Some plants have evolved a more efficient method to fix the CO2 (called C4 photosynthesis) that doesn’t require keeping stomata open all the time (see grasses blog), thus reducing water loss. Stonecrop, and its relatives in the sedum family, Crassulaceae, have taken C4 photosynthesis one step further—not only are they efficient so that stomata are not open much, but the stomata are open only at night.

Most plants are just the opposite! Since photosynthesis can occur only when the sun is up, that’s when they take in CO2 to make sugars. At night, when sugar can’t be made, they shut their stomata to conserve water, even though the lower temperature and higher humidity of night mean less water would be lost then. But these clever succulents have evolved a method to store nighttime-collected CO2 until it can be used the following day. The CO2 is incorporated into organic acid molecules and stored in vacuoles during the night, then converted into a usable molecule for photosynthesis during the day.

This process is called Crassulacean Acid Metabolism, or CAM, named for the sedum family. But it’s not restricted to one family—a variety of very drought tolerant plants use it, including yuccas, agaves, cacti, some orchids, even some unusually drought tolerant ferns. We have several CAM plants on the Berry Prairie, and you may have them where you live, too. 

Written by Dorothy Tuthill, Biodiversity Institute

Prairie Spotlight: Sagebrush

Wyoming residents tend to have a misconstrued conception of sagebrush: “The brown-green stuff that grows everywhere.” Many ranchers would like to reduce its abundance because it is poor livestock food; it competes with preferred grasses for water and nutrients. However, wildlife biologists recognize sagebrush as feed for deer, elk, and pronghorn antelope during the winter. Some view sagebrush as barren land, while others appreciate its unique aroma especially after a summer rain. [1] 

Artemisia tridentata: the name means
3-toothed, a feature of the leaves.

There are five major types of sagebrush in Wyoming: Artemisia cana (Silver sage), Artemisia tridentata (Big sagebrush), Artemisia frigida (Fringed sage), Artemisia nova (Black sage), and Artemisia pedatifida (Birdfoot sage). All of these can be found on the Berry Prairie. 

Artemisia peatifida: this sagebrush is restricted
to most of Wyoming, and only a small part
of south-central Montana.

Why Care about Sagebrush?

Sagebrush is interesting because it grows in places like Wyoming where there is little rain, winters are harsh, and high winds. It depends on the wind for pollination. Second, it provides critically important habitat for a number of wildlife, such as sage grouse, sage thrasher, sage sparrow, and pygmy rabbits.[2]  Third, sagebrush is interesting because the genus belongs to the family Asteraceae, the same family as the sunflower even though it does not have the pretty flowers as the sunflower does. 

Photo by Cody Bish

Finally, sagebrush is an important host plant for a favorite wildflower. It is often used as a host plant for Castilleja or Indian paintbrush. The roots of sagebrush display an opportunistic growth strategy. It produces a taproot that elongates into the ground to reach available soil moisture, and also a network of roots that spreads laterally, giving the Castilleja haustoria roots a network to connect with.




[1] Dennis H. knight Mountains and Plains. The Ecology of Wyoming Landscapes
[2] Pocket Guide to Sagebrush

Written by Jenna Ramunno, Biodiversity Institute

Rock Garden

Penstemon virens is in bloom! It’s a lovely purple gem on the Berry Prairie, but it blooms even better on the rocks of our patio. These rocks—and those all across campus—were collected in the hills to the east of Laramie, and came with their own rock gardens! 

Blue Mist Penstemon (Penstemon virens)

Penstemon is a large genus of wildflowers with snapdragon-like flowers, usually in red, pink, purple or blue. The Berry Prairie is home to five species, one of which white—an atypical color for penstemons. More on that one later—its buds are still small.  “Virens” means green, a reference to the shiny, dark green leaves of P. virens. Despite its relatively small size (usually less than 10”), it provides lots of color this time of year because it’s both abundant and floriferous. It can be grown easily from seed, if you want it in your garden, and can sometimes be found at nurseries, too.

Our rock gardens include more than P. virens:  A quick sampling includes a currant bush, a groundsel, and a scientist on lunch break!

Groundsel growing with penstemon virens

Current bush in the rock

Homo sapien amongst the vegetation

Written by Dorothy Tuthill, Biodiversity Institute

 

So Many Activities!

The green roof is hoppin'.  With so much going on lately, this post might come across a bit scattered.  Apologies for the linear-minded out there!  It's been warm here (it's currently 86.3 degrees), it's field season, and coincidentally we finished a signage project.

Update #1: New Blooms

With the warm weather we've had lately, it's facilitated lots of growth on the roof.  There are two more plants in bloom, the Blue Flag Iris (Iris missouriensis) as well as the Blue Mist Penstemon (Penstemon virens).  The Stonecrop (Sedum lanceolatum) is just about to burst open too, more pictures when that happens.

Can you spot the mason bee pollinating this plant??  Bees (and hummingbirds) love penstemon!

Update #2: Tents

Graduate student Kyle Bolenbaugh is looking at which insects frequent the green roof (in addition to which plants survive the winter cold and summer dryness).  This tent captures insects so Kyle can get a closer look.

Update #3: Signs!

A project a year in the making, we have installed two signs on the railing leading to the green roof to explain what the heck this patch of dirt is.  They're pretty.  Dennis Henry of Click Point Ranch in Denver coordinated the design, manufacturing and installation.  Thanks Dennis!

 

 

Dennis Henry of Click Point Ranch

Stop by to check out all of the activity!  The gate is open and guests are welcome.

Written by Brenna Marsicek, Biodiversity Institute

Dead or Alive

Kyle and Jenna note the living and dead plants within
a plot on the green roof.

Today is survey day.  Kyle Bolenbaugh, the Master's student in Botany studying survivability of the plants on the green roof, is determining which plants survived the winter (and the hectic summer before it).

To do this, Kyle meticulous goes through random plots in different parts of the green roof, and identifies all of the plants within it as well as whether it's alive or dead.  Jenna then marks it down on a spreadsheet.  This is done over the course of multiple years (this is his second survivability count), which allows us to determine survivability over the long term.

Why do we care?

The Berry Prairie is an unusual green roof.  Instead of covering it with a few species of sedum, as is quite common, we went out on a limb to see if we could mimic a prairie, and used 62 species of flowers, grasses and shrubs in the process.  

There are a few other places that have done this (the Church of Latter Day Saints Conference Center in Salt Lake City is one), and we want to be able to say - with data backing our statement - that this strategy does or doesn't work for green roof design.

Heck, if these plants were able to survive being dug up, hauled out to the golf course, plopped there for a couple of months, and replanted just before fall arrived last year, they might be the hardiest of the hardy, and ones we can recommend for use on other green roofs.

For example, Oregon grape (Mahonia repens) and knicknick/bearberry (Arctostaphylus uva-ursi) is very common in natural settings, but completely croaked on the green roof.  Who woulda known?

The Grand Experiment continues - stay tuned for results!

Written by Brenna Marsicek, Biodiversity Institute

Pollinators and Blustery Days

This post is a result of a Laramie citizen, Lindsey, sending in her question about how pollinators deal with wind.  And to address her question is Scott Schell, University of Wyoming Assistant Extension Entomologist.  Scott is a terrific entomologist who helps us a lot with pollinator-related topics, even though his research expertise is grasshoppers.  Thanks Scott!

Do you have a question about or related to the green roof?  Send them in to brenna.marsicek@uwyo.edu and you just might have it featured in the blog!

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Lindsey's Question:

How do pollinators deal with the Wyoming wind?   [A friend] and I were talking about how we didn't know how our fruit trees were going to be pollinated if all the flowers blew away in these crazy winds, given that flowers attract bees.

I've just been pondering how these little buggers go about getting their work done when they weigh so little and southeastern Wyoming has been dealing out 30+ mph winds.


Scott's Answer: 

You have cause to worry about successful pollination of your fruit trees when they bloom during low temperature and/or high wind conditions.  In studies conducted in apple orchards, bad weather can drastically reduce fruit set because it reduces insect pollination visits.     

Honey bees (the Entomological Society of America uses the two word name) generally don’t do much foraging when ambient temperatures are below 55 F and/or when wind speeds exceed 20 to 25 mph.  At the official Laramie NOAA weather station, May, 2013 had 14 days with official highs below 60 F and the wind speeds gusted to over 20 mph everyday except two.   
 

A bumble bee foraging on a low growing pasqueflower
(Anemone patens) in early April.  Scott Schell photo.

On bad weather days, honey bee pollination is usually limited to flowers within a few hundred feet of the hives and the warm, leeward sides of blooming trees within that distance.  Honey bees will also switch to low growing flowers such dandelions, were the wind speed slows at the boundary between the air and ground.  Temperatures are usually much warmer next to the ground on cold, sunny days too.   
 

Native pollinators, such blow flies, sweat bees, digger bees, and bumble bees can handle worse weather conditions, up to point.  Many of the early spring flowering native plants that depend on insect pollination also make it easier for their pollinators by blooming low to the ground were it is warmer and calmer.

 

“Insect Pollination of Cultivated Crop Plants”  USDA ARS Agriculture handbook N. 496