Native and Adapted Grasses for Median Strips

Report and Recommendations for the City of Bozeman

Tracy A.O. Dougher, Professor of Horticulture, Montana State University

tracyaod@montana.edu  (406) 994-6772 
 
Recommendations: • The soil needs to be rock picked prior to planting, particularly for large rocks.  With a limited volume of soil for roots, every cubic inch is valuable for water storage, aeration, and root volume. • Grasses should be seeded in the fall (early September) to obtain at least 3 leaf stage, so that they are ahead of the weeds in the spring. • Native grasses should be planted at a higher density (about 500 Pure Live Seed per square foot).  Seed weights for making these calculations is readily available on grass seed company websites.  • Watering is necessary for establishment (true for any plant, even if it is drought tolerant).  The water truck system is too heavy a watering system and causes seed movement and erosion. • Weeds need to be suppressed in the first year of grass establishment.   Ideally, the median strips should be prepared, watered, and weeds allowed to grow and then sprayed before final tilling and planting.  Even with this preparation, spring spraying with a preemergent, mowing, and summer spraying are necessary in the first summer after planting.  Keeping the grass taller in subsequent years should help suppress the weeds. • No one species or cultivar performed best.  A mix of sheep, hard, and red fescues is recommended for performance.  Anecdotally, the non-research plots (end caps) were a mix of species that took advantage of each species’ outstanding characteristics and suppressed weeds and filled in most quickly.  From this study, the more consistent performers were: sheep fescue – ‘Blue Heron’, hard fescue – ‘Sword’, and red fescue – ‘Boreal’ and ‘Marvel’.   Seed was obtained from Rainier Seed, WA. 
 
Key differences between North and South 27th plots: • Consistent watering to establish the plots (installed sprinkler system) in the South plot, North plot has early water applications from water truck for two weeks and then relied on natural rainfall. • Because the irrigation system in the South plot was adjusted by others, the system watered more initially than should have been. • North plots were larger than South plots (wider median). 
 
Treatments, species and cultivars utilized in this study: • Bare ground • Shredded Cedar bark mulch • Festuca ovina glauca 'Blue Heron' – blue sheep fescue • Festuca trachyphylla 'Blueray' – hard fescue • Festuca trachyphylla 'Sword' – hard fescue • Festuca rubra 'Boreal' – red fescue • Festuca rubra 'Marvel' – red fescue • Festuca ovina 'Covar' – sheep fescue • Poa pratensis ‘SPF-30’ - Kentucky Bluegrass 
 
Methods: Treatments were blocked and replicated three times.  Treatments were 5’ wide strips planted across the 14’ width of the median strip on the north plots, while treatments were 5’ wide strips planted across the 6’ width of the median strip (two replications) and 12’ width of the median strip (one replicate).  Divisions between treatments were indicated with a road feather.  The remaining end caps were planted with a mix of Blue Heron, Sword, and Boreal fine fescues.  Plots were seeded 9/13/15.  North plots were watered in at least twice a week for two weeks while South plots were watered 20 minutes twice a day for three weeks.  Plots were mowed at select times when overrun with weeds. 
Analysis: Key to a dense stand that can combat weeds is rapid increase in percent of grass cover.  Kentucky Blue was the slowest to fill in taking two seasons in both locations.  Marvel, Sword, Boreal, Blue Heron filled in most quickly in the North plots, while the difference between species (except KY blue) was negligible in the South plots.  All grass-planted plots reached >80% cover by the end of the trial. 

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Difference in soil moisture was negligible between species, bare ground, and mulch. The North plots held more moisture over the course of the experiment, most likely because of the wider median strip and larger soil buffering capacity. 0.00 5.00 10.00 15.00 20.00 25.00 30.00 Bare Mulch Marvel Sword KY Blue Blue Heron Covar Boreal Blue Ray Soil Moisture Average - North 0.00 5.00 10.00 15.00 20.00 25.00 30.00 Bare Mulch Marvel Sword KY Blue Blue Heron Covar Boreal Blue Ray Soil Moisture Average - South At each plot site, debris and road splash water and precipitation was collected from the middle and next to the road and profiled. This debris and water has the potential to change the site over time. NM = North plots, Middle of the median strip, NR = North plots, next to the Road, SM = South plots, Middle of the median strip, SR = South plots, next to the Road. Differences between the middle of the plots and next to the road were not discernable. Despite periodic spikes, the overall pH and EC profile did not change. Both debris and water falling into the catch cups were lessened in the second season. The surrounding grass may be preventing debris from falling to the soil level. The South plots purposefully received irrigation in the first year, but water was reduced in both north and south plots in the second year. Roadside catch cups received more debris and water than middle of the plot catch cups in the first season, but were similar in the second season with the established grass and reduced irrigation and precipitation.

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Weeds are the largest issue for the median strips and the biggest reason for mowing. Based on percent weed coverage, best (lowest numbers) overall weed control were found in mulch, Marvel, Sword, and Boreal plots and KY blue, Covar, Marvel, and Boreal, Sword, and Blue Heron all closely matched at the end. Note that weeds in the South plots were much more prevalent on average, but controlled to the same rate at the end point.

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This is a summary report. Detailed methodology and analysis are available from Dr. Tracy Dougher (tracyaod@montana.edu).