The Unseen Benefit of Native Grass

The Unseen Benefit of Native Grass

By Linda Langelo, CSU Horticulture Program Associate

 There is more to grass than just mowing, weed prevention, fertilizing and aerating.  Grass, both hybridized and native grass, plays a very important role in the world not frequently on the minds of grass lovers.  Panicum virgatum, Switchgrass with a deep root system traps coarse sediment and plant nutrients from farm fields.  Yes, that's right, root systems do this.  The unseen part of the grass not only supports the grass's health, but also helps our landscapes filter water.  The larger the area of grass in the landscape, the more opportunity to better filter the water over time especially with types of grasses with deep root systems.  These would be primarily native grasses.

According to Ronald R. Schnabel in his article, Improving Water Quality Using Native Grasses, "Native grasses improve water quality, both in limiting the source of pollutants and intercepting pollutants before they enter a water body."  Native grasses are more than just about conserving water usage, reducing herbicides and fertilizers. 

In fact, native grasses and plants have deeper root systems that can go several feet into the ground. A grass's genetic make-up and environment factors play a role in root depth.  In general, the grass with more top growth also produces a significant amount of root growth to support the top growth.  Big Bluestem, Andropogon gerardi, grows a root system spreading nine feet in the ground.  With roots to this type of depth, we do not usually think about cleaning the water, but rather soil stabilization and a decrease in floodwater.

Buffalo grass used more frequently in home landscapes has a root system that reaches to a depth of eight feet.  The deeper the root system, especially in clay soils, the more water is absorbed and retained in the soil. With the more popular turf grass, Kentucky Blue, the roots reach six to eight inches in depth.

Here is a short list of other native grasses that help with improving water quality and can be added to enhance the natural beauty of the landscape:

Andropogon scoparium   - Little Bluestem

Bouteloua curtipendula   - Side Oats Gramma

Sorghastrum nutans         - Indiangrass

Sporobolus heterolepsis   - Prairie Dropseed

Panicum virgatum            - Switchgrass

Some of these native grasses are very attractive. Most cultivated varieties appear in cultivation.  Some have cultivated varieties have been crossed within the same Genus and now in a hybridized form bears a particular attractive feature that breeders produce. Some are found naturally in the wild and just brought into cultivation. Some are found in seed batches of other cultivated varieties and are called genetic mutations that change the appearance of the plant in some way.  According to Moon Nursery, Dr. Hans Simon spotted Panicum virgatum 'Shenandoah' in a batch of seedlings of Panicum virgatum 'Hanse Hermes'. This seed was an attractive mutation.  It was chosen for its short compact habit and improved red color.  Simon named the plant for Virginia’s Shenandoah Valley as a tribute to the species’ country of origin.  Here are some other cultivated varieties you may be familiar with of Panicum virgatum  listed below.  Many of these cultivated varieties of Switchgrass have been in the trade for over 15 to 20 years.  

1) Cloud Nine - 5 to 6 feet

2) North Wind - 5 to 6 feet

3) Dallas Blues -6 to 8 feet

4) Heavy Metal -2 to 3 feet

5) Shenandoah  -2 to 3 feet

Take a look below at pictures of the native grasses listed above and judge for yourself the merit they might have for a place in your landscape.

Photo credit: www.omcseeds.com Sporobolus heterolepsis

Photo credit: L&H Seeds, Indian Rice Grass

Photo credit: Tri Valley, Side Oats Gamma

Photo credit: North Creek Nurseries, Little Bluestem

 

Photo credit: North Creek Nurseries, Switchgrass

So I hope you look at native grasses differently.  I also must add that grass also produces oxygen.  That goes for all grasses.  There are plenty of native plants that can enhance your native grasses creating beautifully landscaped properties that are sustainable environments. 

This is an early plug for a 2018 conference - Landscaping with Colorado Native Plants, February 10, 2018 at the Denver Botanic Gardens.  Click on the following link for more information: https://landscapingwithcoloradonativeplants.wordpress.com/ .  

Native plants in general have some wonderful qualities.  Please keep this workshop in mind.  

Mulch: More than Just a Pretty Face

By: Alison O'Connor, Horticulture agent, Larimer County Extension

We horties gossip as much as any other office clique...generally about bad gardening advice.  Usually I just roll my eyes at the stuff (something I perfected as a teenager), but this time…it struck a nerve.  Maybe it’s because I’m a huge advocate of that shredded wood we call "mulch", but I felt the need to blog about it.  Whether you agree with me or not…

Fellow blogger, Tony Koski, emailed this link to me and a few colleagues last week, from a blog, called “Grounded Design”.  The author, Thomas Rainer, does have some valid points.  But I just can’t get on board with his philosophy about hating tree mulch rings?  If you choose not to read the article, Mr. Rainer suggests the following about mulch rings at the base of trees:

--They are “ugly” and “have got to go” and “make Swiss cheese out of a continuous lawn”

--They don’t make mowing easier; he states that it’s not difficult to mow around trees, and mulch rings actually require more maintenance [compared to turf]

--Rather than mulching, he suggests planting continuous vegetation to the base of the tree

I do agree with Mr. Rainer on a couple counts.  First, improper mulching is very bad for the tree.  Volcano mulching and covering the flare does lead to stem girdling roots, creates a textural interface that can reduce oxygen availability to the tree’s roots and disrupt water movement to the root ball.  Second, he admits that it does keep mowing equipment and string trimmers away from the base of the tree—one of the main reasons I advocate for mulch.  How many of you have seen trees nicked or wounded from equipment?  It’s tough on the tree (and often leads to decline or death), and it looks horrible.  I’d gladly pick the “Swiss cheese” look over gaping trunk wounds any day. 

If that doesn't make you wince! Ouch.



Clearly the tree "guard" failed.  Mulch may have prevented this from happening.

While his expertise in landscape architecture is admirable…I wonder how he’s never run into the difficulties of growing turf (or other vegetation) under shade trees?  This is a very common question I get each year—“Why can’t I grow [insert plant here] under my mature tree?”  More than likely, it’s because it’s just too darn shady.  Turf needs a minimum of 4-6 hours of sun to grow (more like limp along).  Plus, the tree is sharing water with the lawn—and neither are likely getting enough.  So why would you want to increase the irrigation, and risk killing the tree from overwatering it, in order to grow some grass?  Instead, use mulch and focus your watering efforts on just the tree!  While you can plant shade tolerant perennials or groundcover under trees, I don’t think they are easier to maintain than mulch.  (I just spent the weekend cleaning up my yard—let me tell you—those perennials can be cantankerous.  The scratches on my arms prove it.)

My mother-in-law says it best: mulch is like make-up for the landscape—it looks good and has many benefits…if applied correctly.  In most of our urban areas, water restrictions begin today.  It’s been proven than mulch can reduce water evaporation from the soil surface by up to 70%.  That’s significant.  In addition, a study conducted at the College of DuPage in Illinois by Morton Arboretum staff found that trees that were mulched had significantly greater caliper, crown and root development compared to those with turf growing up to their base (Green and Watson, 1989).  Another study found that mulch modified the soil environment, increased root and shoot growth and aided in plant establishment of desert willow, while turf impaired its establishment (Kraus, 1998).

Trees with mulch rings...does it really look that bad? Is it better to sacrifice tree health at the expense of design?  Trees struggle enough in our tough Colorado climate.

My advice: be sure to mulch, but do it correctly.  Don’t volcano mulch.  Don’t mulch to the trunk (keep it a few inches away).  Don’t have too thick of a layer—2-4” is perfect. Don’t overwater areas that are mulched, since it does hold soil moisture better than unmulched areas.  Keep your rings a diameter of 2-3’ wide (but the wider, the better).  And find a mulch that works for your location and your plants.  So here’s to helping trees with…trees….just little chipped bits of them.