Turf Adaptation & Ecology
  Part 2: Turf communities in Western Oregon




              Tom Cook
         OSU Horticultur...
Turf adaptation implies that commonly planted grasses have specific climatic conditions in
which they thrive. Therefore, i...
Approximate zones of turfgrass adaptation in the lower 48 states

Pacific Coastal Region, Cool Season grasses




        ...
The Pacific Coastal region, the Cool Arid/Semi Arid region, and the Cool Humid region can be compared
on the basis of prec...
30 year ave. precipitation patterns in Cool Season Regions

                   8

                   7
                   ...
30 year ave. HIGH temperatures in Cool Season Regions

            90

            80

            70
                 Pac...
30 year ave. LOW temperatures in Cool Season Regions

            70

            60

            50
                 Paci...
Once you get a feel for the basic differences in climatic regions you can begin to make sense out of
turfgrass adaptation ...
Pacific Coastal (Western Oregon):
The Pacific Coastal region is distinctively different from either the Cool Humid or Cool...
Oregon




    The obvious dividing line in Oregon is the Cascade
    Mountain range. This map image clearly shows that
  ...
Pacific Coastal
    Region




                  The Pacific Coastal Region is defined by winter rains, summer drought,
  ...
The Pacific Coastal Region:
Grasses grow year around here and generally stay green all winter. Lawns cannot
stay green in ...
Pacific Coastal Region
                Lawn Ecology
“ All lawns transition from planted grasses
  to situation specific cl...
Pacific Coastal Region
             Climax Species

vAgrostis sp.         Bentgrasses
vPoa trivialis        Rough Bluegras...
Creeping, colonial, and dryland bentgrass are all part of the soil seed bank
            and are well adapted to wet winte...
Velvetgrass can be found throughout the Pacific Coastal Region and is very
              common in coastal lawns where it ...
Poa trivialis




Roughstalk bluegrass is common throughout the entire Pacific Coastal Region. It is most
active in winter...
Annual bluegrass




Annual bluegrass is ubiquitous in the Pacific Coastal Region. It often shows up in new lawns that
are...
Rat-tail fescue                         July after death

Vulpia myuros



 December after germination




               ...
Where do climax grasses come from?


Ø   Contaminated seed or sod
       eg. Poa trivialis or bentgrass in P rye

Ø   Pers...
Lawn Moss




Mosses also have a special niche in Pacific Coastal lawns. They grow well where other plants can’t grow
and ...
English daisy                     White clover




                                               Black medic
            ...
A Species Rich Climax Lawn




This is a perfect example of a climax lawn growing in shade on a fairly wet infertile site....
When you plant a straight perennial ryegrass lawn, it initially is pure with no apparent contaminants.
If the site is clea...
Young commercial site planted to 100% perennial ryegrass




                                                             ...
Ryegrass to bentgrass conversion
2 yrs                                                            3 yrs




6+ yrs        ...
10 yr old climax lawn in Seattle




Climax lawns are often very nice lawns. They are persistent, require very little fert...
60+ yr old climax lawn in Seattle




This beautiful lawn is almost solid bentgrass.
                                     ...
“ The primary selective pressure
 in the Pacific Coastal region may
 be the lack of environmental
 extremes”
             ...
Pacific Coastal Lawn Ecology Rule # 1

     Plants that grow well fall through
     spring or at least maintain density,
 ...
This Kentucky bluegrass lawn in Corvallis, Oregon was in its first winter after planting. The
brown grass is the Kentucky ...
Annual bluegrass and Poa trivialis in a young ryegrass lawn.




On irrigated and fertilized perennial ryegrass lawns, ann...
When all is said and done, plan on some form of a climax lawn. Once the climax stand
develops you will have a surprisingly...
Bentgrass climax lawn in Lake Oswego, OR




Other than regular mowing and periodic irrigation this lawn receives very lit...
Bentgrass Climax




Even as hot as it gets in Grants Pass in summer, this climax bentgrass lawn is   Grants Pass, OR
doin...
Qualities of Climax Lawns
   in the Pacific Coastal Region



ØBetter at lower mowing heights
ØColor is lighter green
ØReq...
Pacific Coastal Region
          Succession Rule # 2


“Maintenance intensity determines the
 succession endpoint”

      ...
Potential succession end points
              in the Pacific Coastal Region

                                         Pere...
Why does low N ryegrass get out competed?

 Brown Blight                                                    Rust




Even ...
Transitioning ryegrass lawn in Seattle




We hear about the perils of over fertilizing but in truth most lawns are under ...
English Daisies in climax ryegrass/bentgrass/Poa annua turf




English daisy is a common component of lawns under low fer...
Climax lawn in Portland, OR
               Bentgrass/Poa annua/Poa trivialis/ Veronica climax




This site is wet in wint...
Bentgrass/Poa trivialis/Clover climax                                   Corvallis, OR




This lawn has been fertilized wi...
Summer drought impact

                                     Perennial Ryegrass


                  Stand thins as ryegrass...
Perennial rye clumping out                                      Climax bent lawn in fall




                             ...
July after death
  Rat-tail fescue



   December after fall germination




After many years without summer irrigation, e...
English daisy                     White clover




Black medic



False dandelion




                                    ...
Bentgrass/ Rat-tail fescue/ False dandelion climax




This mix of grasses and False dandelion is one of the most common c...
Low input lawns: Pacific Coastal Region

Irrigated climax:
Bentgrass / Poa trivialis / clover
Transition occurs in 3-10 yr...
Potential succession end points
                    in the Pacific Coastal Region



                                     ...
Why does annual bluegrass dominate under high N?




                                                                 Leaf...
In this photo you can see the brown and thin Kentucky bluegrass that has been riddled by leaf spot and
the vigorous green ...
High N, irrigated
               annual bluegrass climax




This lawn has long been maintained with regular fertilizer ap...
Typical Poa annua golf course in Portland , OR
                     Potential Climax end points


                        ...
High input turf: Pacific Coastal Region

  All areas transition to Poa annua
  with remnants of planted grasses.




     ...
Summary:

The bottom line in the Pacific Coastal Region, which includes western
Oregon, is that the commonly planted domes...
References:

All maps used in this presentation were created and copyrighted by Ray Sterner
at the Johns Hopkins Universit...
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Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

  1. 1. Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon Tom Cook OSU Horticulture Dept. 2008
  2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 28. 60+ yr old climax lawn in Seattle This beautiful lawn is almost solid bentgrass. T Cook photo
  29. 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. 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. 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. 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. 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. 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. 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. 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. 37. Pacific Coastal Region Succession Rule # 2 “Maintenance intensity determines the succession endpoint” Factors: N fertility Irrigation intensity Herbicide use
  38. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 55. High input turf: Pacific Coastal Region All areas transition to Poa annua with remnants of planted grasses. T Cook photo
  56. 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. 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/

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