1. Turf Adaptation & Ecology
Part 2: Turf communities in Western Oregon
Tom Cook
OSU Horticulture Dept.
2008

2. Turf adaptation implies that commonly planted grasses have specific climatic conditions in
which they thrive. Therefore, if we know the climate we should be able to predict what grasses
will have a reasonable chance to prosper. The converse is also true. If we plant grasses in climates
where they are not adapted, we can expect to have problems growing a healthy lawn. One way to
depict turf adaptation is through maps. Authors have long drawn maps of the USA that carve up
the country into zones or regions that define both the climate and the best adapted grasses. Early
maps were simple and divided the country up into cool season and warm season areas. Where the
two basic regions intersected was a fuzzy zone generally referred to as the transition zone.
Over time maps have become more intricate and somewhat standardized in their depiction of the
important climatic zones. What follows is my interpretation of general climatic regions in the USA as
they relate to grass adaptation. I have created a new zone that is not commonly found in most
textbooks. What I call the Pacific Coastal region has historically been lumped in with the Cool Humid
region. My reason for separating it into its own region should become clear as you study the three
slides following the generalized map of the USA.
Maps that depict zones of grass adaptation have obvious limitations. A generalized map cannot
account for all of the microclimate areas in a zone. It also cannot account for climatic changes
associated with changes in altitude. An example is Hawaii where the climate at sea level can be
either Warm Arid or Warm Humid depending on which side of the islands you are on. On one
island, the climate can change to Cool Humid as you drive up into the mountains. The key is to use
maps as general conceptual guides to zones of adaptation and realize that there will be many
exceptions in any given region. Maps can only give you a very general notion of regions.
Note on the following map that humidity and rainfall changes from high in the Pacific Coastal zone
to very low in the Cool Arid zone. As you move east the humidity begins to increase along with
summer rainfall so that in the Cool Humid zone you have high humidity and fairly consistent summer
rainfall. A similar process occurs from the Warm Arid to the Warm Humid zones.

3. Approximate zones of turfgrass adaptation in the lower 48 states
Pacific Coastal Region, Cool Season grasses
Cool Humid Region
Cool Arid, Semi-arid region Cool Season grasses
Cool Season grasses
Warm Humid Region
Warm Season grasses
Warm Arid, Semi-arid Region
Warm Season grasses
Transition Zone
See references at the end of this slide show for Cool and Warm Season grasses
credits and additional information regarding the maps.

4. The Pacific Coastal region, the Cool Arid/Semi Arid region, and the Cool Humid region can be compared
on the basis of precipitation patterns, average monthly high temperatures, and average monthly low
temperatures.
Precipitation patterns: Study the following slide and you will see the differences in both quantity and
monthly distribution of precipitation in these three zones. Most notable is that while the total
precipitation in the Pacific Coastal zone is high, it is actually very dry during summer and very wet in
winter. This alone separates it from the Cool Humid region where summer rainfall is the norm. It is
possible to have functional turf in parts of the Cool Humid region in most years even without regular
irrigation. In the Pacific Coastal region grass will only be green in summer if it receives regular irrigation.
Average monthly high temperatures: The second slide in this series shows the average monthly high
temperatures for the three cool season regions. Note that there is not a lot of difference between
monthly highs for the three regions during the summer period. Likewise the Cool Arid and Cool Humid
regions have very similar winter high temperatures. The Pacific Coastal region again stands out because
it has notably warmer winter high temperatures than the other regions.
Average monthly low temperatures: The third slide in this series shows the average monthly low
temperatures for the three cool season regions. Again note the similarities between average low
temperatures in winter between the Cool Arid and Cool Humid regions. The Pacific Coastal region stands
out because the average low temperatures in winter are considerably higher than the other regions. You
will also see that the average low temperatures in the Cool Humid region are notably higher than those
in the Cool Arid region. This probably reflects greater radiation cooling in the Cool Arid region. This is
especially pronounced in high desert areas of the Cool Arid region where night temperatures even in
summer can drop near freezing.
Note: The graphs depicted in these slides are based on monthly values averaged over several key cities
within each region. For example the Pacific Coastal region values are the average of Seattle, Portland,
Salem, and Corvallis.

5. 30 year ave. precipitation patterns in Cool Season Regions
8
7
Pacific Coastal
6
Inches per month
5
Cool Humid
4
3
2
1
Cool Arid
0
J F M A M J J A S O N D
Pacific Coastal Region Cool Arid Region Cool Humid Region

6. 30 year ave. HIGH temperatures in Cool Season Regions
90
80
70
Pacific Coastal
60
Degrees F
50
40
Cool Arid
30
20
Cool Humid
10
0
J F M A M J J A S O N D
Pacific Coastal Cool Arid Cool Humid

7. 30 year ave. LOW temperatures in Cool Season Regions
70
60
50
Pacific Coastal
Degrees F
40
30 Cool Arid
20
Cool Humid
10
0
J F M A M J J A S O N D
Pacific Coastal Region Cool Arid Region Cool Humid Region

8. Once you get a feel for the basic differences in climatic regions you can begin to make sense out of
turfgrass adaptation in each region.
Cool Humid: Grasses in this region are subject to freezing winters and fairly warm humid summers. The
cool humid region tends to have four distinct seasons with short springs and long summers followed by
nice crisp fall weather before entering into long and often cold winters. Grasses go dormant in winter
followed by a green up period and a flush of growth in spring. Summer is a stress period with often
excessive heat that causes root system dieback. Summer rainfall and high humidity leave grasses open
to significant summer disease pressure. Insect pressure is significant in most years. The actual period
for optimum growth can be as short as 4 months in this region. The rest of the year the grass is under
either heat, drought, or cold stress.
Key grasses here include Ky. bluegrass, perennial ryegrass, fine fescues, tall fescue, with creeping
bentgrass being widely used on golf courses. Annual bluegrass is also common on golf courses but is
generally considered a weed because it often dies from the many stresses it encounters. Disease
and insect resistance are important considerations when selecting grasses here. Crabgrass and other
summer annual grasses are consistent problems throughout the region.
Cool Arid: For the most part turf can only be grown in this region if supplemental irrigation water is
used. With water, this is a fairly easy region to grow cool season grasses. In general, winters are cold
with variable snow cover. Desiccation injury is probably more important than cold injury in most winters.
Summers, while often very hot, are moderated in high elevations by cool night temperatures and in
general by low humidity. Spring is short and falls tend to be clear and crisp. The low precipitation
year around and the low humidity in summer really separate this area from the cool humid region.
Key grasses here are the same as the Cool Humid region. Ky. bluegrass, fine fescue, and tall fescue all
thrive here. Perennial ryegrass does well but may be prone to cold or desiccation injury in winter.
Creeping bentgrass is common on golf courses and annual bluegrass is a major climax species on older
golf courses. Buffalograss, a cold hardy warm season grass can be grown in eastern parts of this region.
Disease, insect and weed pressure are generally lower than in the Cool Humid region.

9. Pacific Coastal (Western Oregon):
The Pacific Coastal region is distinctively different from either the Cool Humid or Cool Arid regions.
A typical growing season here is long and less well defined than in the other regions. In a normal year,
grass is green for 12 months and is actively growing for 10 months. It is not unusual for grass to be
cut all year long. Spring generally starts in February and continues to June. Summer runs from
mid-June to mid-Sept and fall lasts often through November. Generally, during summer, night
temperatures cool down significantly even when daytime temperatures are high. Humidity is inter-
mediate between the Cool Humid region and the Cool Arid region. Diseases are more likely to be a
problem in winter than in summer, and insect pressure is mild compared to other regions. Annual weedy
grasses occur but are not consistent problems. Lawns can survive without irrigation in most years, but
they will be dormant all summer.
The grasses used in the Cool Humid and Cool Arid regions are commonly planted in the Pacific Coastal
region, but tend not to dominate lawns for long. In fact most are replaced rapidly by naturalized grasses
that persist and compete better over time. I divide grasses for this area into the commonly planted
grasses and the climax grasses which eventually dominate lawns.
Commonly planted grasses include perennial ryegrass, fine fescues, and tall fescue. Creeping bentgrass
is planted on greens, tees, and fairways at golf courses and colonial bentgrass is often planted on tees
and fairways. Ky. bluegrass has historically not performed well in this region and is rarely planted.
Climax grasses include colonial, dryland, and/or creeping bentgrass, roughstalk bluegrass, annual
bluegrass, velvetgrass, and rat-tail fescue. A typical irrigated lawn in the Pacific Coastal region will
contain most or all of these grasses plus remnants of the planted grasses once conversion has occurred.
Non irrigated lawns will often devolve into bentgrasses and rat-tail fescue. Rat-tail fescue has a
unique niche because it is a winter annual that germinates in late fall grows through winter and dies
after setting seed in early summer.

10. Oregon
The obvious dividing line in Oregon is the Cascade
Mountain range. This map image clearly shows that
Western Oregon is distinctly different from
Central and eastern Oregon
See references at the end of this slide show for
credits and additional information regarding the maps.

11. Pacific Coastal
Region
The Pacific Coastal Region is defined by winter rains, summer drought,
Cool Arid Region
medium to high humidity, and moderate to mild temperatures. Grass
stays green during winter and requires irrigation in summer to stay green.
See references at the end of this slide show for
credits and additional information regarding the maps.

12. The Pacific Coastal Region:
Grasses grow year around here and generally stay green all winter. Lawns cannot
stay green in summer without supplemental irrigation.
Planted grasses: Perennial ryegrass, fine fescues, tall fescue
Climax grasses: Bentgrasses, rough bluegrass, annual bluegrass,
velvetgrass, rat-tail fescue
Insects: European Crane fly, Billbugs, Black cutworm
Diseases: Red thread, Leaf spots, Rust, Fusarium Patch,
Take-all Patch
Weeds: False dandelion, Common dandelion, Clovers,
Mousear chickweed, Black medic,moss, others.

13. Pacific Coastal Region
Lawn Ecology
“ All lawns transition from planted grasses
to situation specific climax vegetation”
or
What you plant is not what you get!
This reality is what makes the Pacific Coastal Region so unique. In most other parts of the northern USA, when you
plant a lawn, you will end up with the grass you planted. If other grasses are present, you got bad seed or you imported
an undesirable grass with the soil you used to construct the lawn. In our area, it doesn’t matter what you do, you will end
up with other grasses invading and likely dominating the site.

14. Pacific Coastal Region
Climax Species
vAgrostis sp. Bentgrasses
vPoa trivialis Rough Bluegrass
vPoa annua Annual Bluegrass
vHolcus lanatus Velvetgrass
vVulpia myuros Rat-tail Fescue
vPlanted grasses
vVarious moss species
vNumerous dicot species

15. Creeping, colonial, and dryland bentgrass are all part of the soil seed bank
and are well adapted to wet winters and summer drought or summer irrigation.
They can produce dense turf with very little fertilizer nitrogen. They are the
most competitive grasses under moderately low input conditions. Most older
lawns have significant amounts of bentgrass in them.
Bentgrass
T Cook photo

16. Velvetgrass can be found throughout the Pacific Coastal Region and is very
common in coastal lawns where it is often as the dominant component. I find
it in most lawns in the Willamette Valley though occasionally it is absent.
This isn’t a very pretty grass but it is tough and handles both wet and dry
Velvetgrass soils.
T Cook photo

17. Poa trivialis
Roughstalk bluegrass is common throughout the entire Pacific Coastal Region. It is most
active in winter when it grows more vigorously than all other grasses. It handles wet soils
very well and spreads via stolons. In the spring it gets very coarse and stemmy when it
moves into flower mode. It struggles in heat and drought but survives all stresses. It is a
major component of the soil seed bank and is a common contaminant in seed mixes, so it
can be found in almost all lawns.
T Cook photo

18. Annual bluegrass
Annual bluegrass is ubiquitous in the Pacific Coastal Region. It often shows up in new lawns that
are planted late in the fall. It is a major component of all old golf courses and produces great
putting turf. In homelawns, it generally dominates lawns that ar e over watered and over fertilized.
It is a prolific seed producer and is a major part of the soil seed bank. It is least likely to be a
significant component in old bentgrass lawns that are unfertilized and sparingly watered.
T Cook photo

19. Rat-tail fescue July after death
Vulpia myuros
December after germination
Rat-tail fescue is a true winter annual with a
special niche in lawns that receive no irrigation
at all. It is a beautiful grass that germinates
with the onset of fall rains, grows through
winter, flowers in spring and dies in June. It is
perfectly suited to our Mediterranean climate.
Rat-tail fescue has increased significantly in
recent years as more people have quit irrigating
their lawns. As the perennial grasses thin out
or die, this grass is perfectly suited to fill the
void.
T Cook photos

20. Where do climax grasses come from?
Ø Contaminated seed or sod
eg. Poa trivialis or bentgrass in P rye
Ø Persistent soil seed bank
eg. Poa trivialis Roughstalk bluegrass
Poa annua Annual bluegrass
Agrostis Bentgrasses
Holcus Velvetgrass
Vulpia Rat-tail fescue

21. Lawn Moss
Mosses also have a special niche in Pacific Coastal lawns. They grow well where other plants can’t grow
and are well suited to infertile soils, shady sites and wet soils. They require no fertilizer and can
survive drought by simply drying up. As soon as the fall rains return, dried plant fragments green up
and grow all winter. In general, the wetter the winter the more vigorous the moss.
T Cook photos

22. English daisy White clover
Black medic
Black medic
False dandelion Mousear Chickweed
Unless herbicides are used to control them, there will always be a variety of dicot plants in lawns. They
all are adapted to drought, low fertility, fall germination cycles, etc., which makes them competitive
and persistent. Many dicots are very compatible with grass and help create a stable mix of
False covers generally in low input lawns.
ground dandelion
T Cook photos

23. A Species Rich Climax Lawn
This is a perfect example of a climax lawn growing in shade on a fairly wet infertile site. The
grasses include mostly bentgrass and roughstalk bluegrass. The dicots include white clover and
speedwell (Veronica filiformis). With regular mowing, this lawn will sustain itself for a very long
time with only periodic watering in summer.
T Cook photo

24. When you plant a straight perennial ryegrass lawn, it initially is pure with no apparent contaminants.
If the site is clean, it will stay pure for at least a few years, but eventually other grasses will move in.
New perennial ryegrass sod lawn in Seattle, WA
T Cook photo

25. Young commercial site planted to 100% perennial ryegrass
Poa trivialis
Holcus lanatus
Seeded lawns often develop contaminants within a year of planting. Initially contaminants come from
the soil seed bank. Another source it dirty seed. On this site there was a fair amount of velvetgrass
and roughstalk bluegrass on the site. I also found quite a bit of bentgrass. It won’t take long for this
lawn to convert to the climax grasses.
T Cook photos

26. Ryegrass to bentgrass conversion
2 yrs 3 yrs
6+ yrs 5 yrs
These photos show the progression from a few isolated spots to total domination in just a few
short years. This happens to almost all lawns in the Pacific Coastal Region.
T Cook photos

27. 10 yr old climax lawn in Seattle
Climax lawns are often very nice lawns. They are persistent, require very little fertilizer, look nice
when irrigated regularly, and survive quite well without irrigation by going dormant.
T Cook photo

28. 60+ yr old climax lawn in Seattle
This beautiful lawn is almost solid bentgrass.
T Cook photo

29. “ The primary selective pressure
in the Pacific Coastal region may
be the lack of environmental
extremes”
or
Everything grows but nothing dominates
In much of the northern USA, conditions are generally unfavorable for lawn grasses. The combination of hot humid
summers and cold miserable winters mean that only the toughest grasses can survive. Generally, if you plant one of the
adapted grasses and provide appropriate maintenance, the lawn will stay fairly pure.
In the Pacific Coastal Region, our mild weather is suited to nearly every cool season grass. Tolerance of grasses to
extreme temperatures is of minor importance. Grasses that would appear to be relatively weak often do very well
here. The result is a sort of ‘free for all’ in which everything grows at some time of the year but no one grass dominates in
all situations. The average lawn will have anywhere from three to six different grasses along with numerous broadleaf plants.

30. Pacific Coastal Lawn Ecology Rule # 1
Plants that grow well fall through
spring or at least maintain density,
will eventually dominate the stand.
or
“Competition occurs in the cool months”
In the most common scenario that I see, grasses like bentgrass, annual bluegrass, and roughstalk bluegrass tend to show
up in new lawns during the first winter after planting. Depending on intensity of maintenance, one or more of these will
spread and begin to form distinct patches. Most of their spread will occur during the nine cool months when they are more
vigorous than the planted grasses. Even if they go dormant in summer, they will recover and spread during fall through
spring and will eventually dominate most lawns.

31. This Kentucky bluegrass lawn in Corvallis, Oregon was in its first winter after planting. The
brown grass is the Kentucky bluegrass and the green tufts included a variety of invading species
that either came from the sod or were in the soil seed bank. Thi s lawn has since converted
to all climax species and I doubt if I could find any Kentucky bluegrass at all.
T Cook photo

32. Annual bluegrass and Poa trivialis in a young ryegrass lawn.
On irrigated and fertilized perennial ryegrass lawns, annual bluegrass is often the first and most
successful invader. Note how well it grows in winter. One of the qualities that make annual bluegrass
so competitive is the density it achieves. Add in vigorous spring flower and seed production and it
will easily dominate all other grasses.
T Cook photo

33. When all is said and done, plan on some form of a climax lawn. Once the climax stand
develops you will have a surprisingly easy lawn to maintain.
Climax lawn in Seattle, WA
T Cook photo

34. Bentgrass climax lawn in Lake Oswego, OR
Other than regular mowing and periodic irrigation this lawn receives very little
in the way of inputs.
T Cook photo

35. Bentgrass Climax
Even as hot as it gets in Grants Pass in summer, this climax bentgrass lawn is Grants Pass, OR
doing just fine.
T Cook photo

36. Qualities of Climax Lawns
in the Pacific Coastal Region
ØBetter at lower mowing heights
ØColor is lighter green
ØRequire less fertilizer
ØLimited drought resistance
ØLong lived soil seed bank
ØStrong winter competitors

37. Pacific Coastal Region
Succession Rule # 2
“Maintenance intensity determines the
succession endpoint”
Factors:
N fertility
Irrigation intensity
Herbicide use

38. Potential succession end points
in the Pacific Coastal Region
Perennial Ryegrass
High N Low N
N responsive Low N responsive
grasses dominate plants dominate
Annual Bluegrass Bentgrass, moss, clover
Climax Climax
Irrigation and fertilization are two major factors that influence how lawns evolve. In this case, assuming the site is
irrigated, fertilization practices will drive the succession to either bentgrass or to annual bluegrass. The next few slides
follow the events that occur if the lawn is maintained under low fertility.

39. Why does low N ryegrass get out competed?
Brown Blight Rust
Even though perennial ryegrass is the most commonly
planted grass throughout the region, it is a relatively
poor competitor over time. When under low fertility,
Red thread
ryegrass suffers from several diseases that tend to thin
it out. When that happens, the stand is ripe for invasion by
grasses better suited to low fertility.
Brown blight, rust, and red thread rarely kill any grass but
they can thin it out during fall and winter when it is not a
good time to force new growth with fertilizer. If you do
fertilize, it may simply be out competed by annual bluegrass
or roughstalk bluegrass. T Cook photos

40. Transitioning ryegrass lawn in Seattle
We hear about the perils of over fertilizing but in truth most lawns are under fertilized. When
you plant a grass like perennial ryegrass that requires regular nitrogen applications to maintain
density, it will likely be invaded by species that do well with minimal fertilizer. This park lawn in
Seattle is rapidly being taken over by white clover which can fix nitrogen and grow well without
added fertilizer.
T Cook photo

41. English Daisies in climax ryegrass/bentgrass/Poa annua turf
English daisy is a common component of lawns under low fertility and subjected to moderate
drought stress in summer. If the site is wet in winter they grow even better.
T Cook photo

42. Climax lawn in Portland, OR
Bentgrass/Poa annua/Poa trivialis/ Veronica climax
This site is wet in winter and receives shade in the afternoon in summer. Under low fertility the
lawn has evolved into a broad based mix of grasses and Veronica species. It is beautiful in spring
when the blue flowers of the Veronica are out.
T Cook photo

43. Bentgrass/Poa trivialis/Clover climax Corvallis, OR
This lawn has been fertilized with nitrogen on average once every 4 years. It is dominated by
bentgrass and clover, with roughstalk bluegrass showing up during winter. There is very little
annual bluegrass. It gets irrigated approximately once per week for most of the summer period.
T Cook photo

44. Summer drought impact
Perennial Ryegrass
Stand thins as ryegrass
Drought tolerant dicots invade.
goes dormant. Some plants die .
Ryegrass stand
Weeds germinate in fall.
thins to clumps.
Invading dicots:
Invading grasses:
Clover
Dryland bent
False dandelion
Velvetgrass Common yarrow
Rat-tail fescue Mousear chickweed
Summer drought influences both the type of broadleaf plants and the mix of grasses that dominate the site. Since over
60% of the lawns in the Willamette Valley of Oregon are not irrigated regularly, drought impacts are important.

45. Perennial rye clumping out Climax bent lawn in fall
Bentgrass doesn’t stay green under drought. It turns
Ryegrass can withstand a fair amount of drought, but when brown and goes dormant very quickly. When the fall
drought is too severe many individual plants die leaving open rains come, it starts to regrow and slowly fills in by
areas for invading grasses. the spring period as noted below.
Bent rhizomes recovering Climax bent lawn in spring
Bentgrass recovers from crowns
and rhizomes primarily. T Cook photos

46. July after death
Rat-tail fescue
December after fall germination
After many years without summer irrigation, even bentgrass stands will decline and the trend moves
toward invasion by this winter annual. In some respects, Rat-tail fescue is the ultimate climax grass
in unirrigated lawns. It is usually joined by False dandelion, which is our most drought tolerant
broadleaf invader.
T Cook photos

47. English daisy White clover
Black medic
False dandelion
Mousear Chickweed
False good fall germinators and survivedrought include the p lants shown here.
dandelion
Other broadleaf plants suited to prolonged
Most are drought by seed, dormancy, or
T Cook photos
resistance.

48. Bentgrass/ Rat-tail fescue/ False dandelion climax
This mix of grasses and False dandelion is one of the most common climax lawns
that I see from the Willamette Valley of Oregon to Vancouver, BC Canada.
T Cook photos

49. Low input lawns: Pacific Coastal Region
Irrigated climax:
Bentgrass / Poa trivialis / clover
Transition occurs in 3-10 yrs.
Non-irrigated climax:
Bent./ Rat-tail fescue/ False dandelion
Transition occurs in 10+ years.

50. Potential succession end points
in the Pacific Coastal Region
Perennial Ryegrass
High N Low N
N responsive Low N responsive
grasses dominate plants dominate
Annual Bluegrass Bentgrass, moss, clover
Climax Climax
Even though most lawns are maintained under low fertility, there are many sites that receive regular fertilizer and
regular irrigation. Under those conditions a different sort of climax lawn emerges.

51. Why does annual bluegrass dominate under high N?
Leafspot
Fusarium patch
Fusarium patch
Just as with low fertility, diseases play an important role
in determining which grasses dominate under higher fertility.
Two important diseases include Fusarium patch and various
leaf spot diseases. When these attack perennial ryegrass
they cause severe thinning typically in winter. This allows
grasses like annual bluegrass to invade and take over.
T Cook photos

52. In this photo you can see the brown and thin Kentucky bluegrass that has been riddled by leaf spot and
the vigorous green annual bluegrass that is rapidly filling in. It won’t take long for the annual bluegrass
to dominate.
Aggressive winter growth
Turf thinning from high N diseases
T Cook photo

53. High N, irrigated
annual bluegrass climax
This lawn has long been maintained with regular fertilizer applications and regular irrigation. It is almost
100% annual bluegrass.
T Cook photo

54. Typical Poa annua golf course in Portland , OR
Potential Climax end points
Perennial Ryegrass
High N Low N
N responsive Low N responsive
grasses dominate plants dominate
Annual Bluegrass Bentgrass, moss, clover
Climax Climax
Long term consistent care will inevitably result in golf courses dominated by annual bluegrass.
T Cook photo

55. High input turf: Pacific Coastal Region
All areas transition to Poa annua
with remnants of planted grasses.
T Cook photo

56. Summary:
The bottom line in the Pacific Coastal Region, which includes western
Oregon, is that the commonly planted domesticated grasses such as
perennial ryegrass, the fine fescues, tall fescue, and Kentucky bluegrass
will eventually be invaded by other grasses that were generally not
planted. Most will also develop a resident dicot population
Which plants dominate depends on the level of fertility and the intensity
of irrigation and other cultural practices. Low input irrigated lawns will
often be dominated by bentgrasses, roughstalk bluegrass, and clover or
other site specific dicots. Unirrigated lawns will generally be dominated
by bentgrasses, Rat-tail fescue, and False dandelion. Lawns that are
irrigated and fertilized regularly will often be dominated by annual
bluegrass.
To the extent they are used, herbicides will determine what if any dicots
are present, but will have little impact on the grass composition.

57. References:
All maps used in this presentation were created and copyrighted by Ray Sterner
at the Johns Hopkins University Applied Physics Laboratory. The maps are licensed
to North Star Science and Technology, LLC from which permission was granted for
use in this presentation.
Information regarding the maps and images can be located at
http:// fermi.jhuapl.edu/states/