Growing Great Turf in Shade

1
Growing Great Turf in Shade

• Dr. John Stier
• Dept. Horticulture
• University of Wisconsin

Photo courtesy Bill Leuenberger
2
Adaptation of Turfgrasses

• Evolved in Eurasia
• Grazing pressure
• Outer edges of forests

3
Why Turf Dies in Shade

• Lack of light
• Diseases
• Tree root competition
• Traffic exacerbates problem

4
Shade Environment

• Reduced light
• Moderated temperatures
• Low air movement
• High humidity
• Long periods of leaf wetness

5
Reduced Light

• Quantity
• Full sun 2,000 micromoles m-2 sec-1
• 50 mol per day
• 50 shade physiological problems
• 70 shade noticeable decline
• 10-20 shade growing limit
• Quality
• Less blue, more red
• Etiolation occurs

6
Photosynthesis Respiration

• Photosynthesis
• Sunlight CO2 Chemical energy O2
• During sunny periods
• Respiration
• Chemical energy ? CO2 H2O
• 24 hrs/day, 7 days/wk
• Compensation point
• Photosynthesis Respiration

7
Sunlight

• Summer solstice 50- 60 mol PAR m2/day
• Cool-season grasses
• Reduced growth lt 15-18 mol
• Poor recovery/death lt 7.5 mol
• Warm-season grasses
• Reduced growth lt 25 mol

8
Annual Variation of Sunlight
Mols PAR day-1
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Diurnal Variation of Sunlight
Mols PAR hr-1
Hour of Day
10
Morning vs Afternoon Sun

• Morning sun best
• 4-6 hrs minimum
• Afternoon
• Higher temperatures photorespiration

11
Tree Shade Changes Light Quality
Photo courtesy Bill Leuenberger
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Light Comes in Waves of Particles
Blue Red
Blue Red
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Shade Affects Photosynthesis
Sunny Shaded
CO2
O2
O2
CO2
CO2
O2
CO2
CO2
O2
O2
CO2
CO2
O2
CO2
O2
CO2
CO2
Carbohydrates C6H12O6
Carbohydrates C6H12O6
14
Physiological Changes

• Vascular system degenerates
• Thinner cell walls cuticle
• Reduced photosynthesis
• Loss of carbohydrates
• Excessive gibberellic acid (GA)

15
Turf Responds to Low Light

• Fewer leaves
• Longer, narrower leaves
• Thinner cuticle, thinner leaves
• Less roots, less rooting depth
• Vascular system breaks down

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Diseases

• Microdochium patch
• (pink snow mold)
• Powdery mildew

Microdochium mycelium on Kentucky bluegrass at
10 light
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Powdery mildew on Supina
bluegrass Kentucky bluegrass resista
nce to powdery mildew
18
Tree Root Competition
Photo courtesy Bill Leuenberger
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Tree Root Competition

• Water
• Nutrients
• Space
• Allelopathy
• Can go both ways

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Connecting Pot Experiment (Whitcomb, 1972, Agron.
J. 64355-359)

• Shade
• No shade

Turf
Tree
Tree roots
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Turf Sod Weight Affected by Shade and Tree Roots
b
c
b
a
b
ab
b
Fresh weight (g)
a
a
a
a
a
a
a
a
a
Whitcomb, Agron. J. 64355, 1972
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Managing Turf in Shade

• Prune trees, remove shrubs
• Minimum branch height 10 ft
• Avoid tree bark injury
• Maintain aesthetics
• Certified arborist
• Tree root pruning not usually advisable
• Plant low density trees
• Lindens, birches
• Avoid oaks, maples

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Selective Pruning
After
Before
Temporary fix
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Managing Turf in Shade

• Mowing
• Increase height 3-4 inches
• Fertilization
• Maintain frequency (3-4 times/yr)
• Cut rate in half (0.5 lb N/1000 ft2)
• 30-50 slow-release N
• Irrigation
• Deep, infrequent
• Early in day

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Fertilization Requirements

• ½ rate
• Same frequency (May, July, Sept, Nov)
• Nitrogen type?

Photo courtesy Bill Leuenberger
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Nitrogen Assimilation into Grasses
Amino acids, proteins
Glutamate
NH4
NH4
Grass root
NO3-
NO2-
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Nitrogen Response of Turf Quality in Shade
Depends on Turf Species (Verona, WI, 2001)
a
b
c
ab
c
c
Steinke Stier, 2003
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Kentucky bluegrass Granular N
Foliar N
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Plant Shade Adapted Grasses

• Fine tall fescues
• Bentgrasses, rough bluegrass
• Perennial ryegrass
• Kentucky bluegrass

GOOD POOR
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Turf Species for Shade

• Relative shade tolerances
• Supina bluegrassgtrough bluegrass, fine fescue,
  tall fescuegtbentgrassgtperennial ryegrassgtKentucky
  bluegrass
• Moist shade Supina or rough bluegrass
• 10 or more in mixture
• Dry shade Fine fescue or tall fescue
• Chewings, creeping red, hard fine fescues
• Do not mix with other types

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Supina Bluegrass

• Native to sub-alpine Europe
• Stoloniferous
• Shade and traffic tolerant

Poa supina plant and stolons
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Comparison of Supina and Kentucky Bluegrasses
Under Traffic and 85 Shade for 6 Months
Powdery Mildew Poa pratensis P. supina
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Some PGRs Inhibit Gibberellic Acid (GA) Synthesis

• Paclobutrazol (Scotts Turf Enhancer, Trimmit)
• Flurprimidol (Cutless)
• Trinexapac-ethyl (Primo)

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PGR-Shade Research 1992-20025-20 Sunlight

• Increased chlorophyll concentration (Stier
  Rogers, 2001)
• Increased photosynthesis (Stier, 1997 Qian
  Engelke, 1999)
• Increased carbohydrates (Qian Engelke, 1999)
• Increased tillering 2-3X
• (Stier Rogers, 2001)
• Enhanced traffic tolerance
• (Stier et al., 1999)
• Stop GA production
• (Qian et al., 2002)

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Mow High
Shaded Turf Management
Use half-rates when fertilizing
Deep, infrequent irrigation Prune
trees/shrubs judiciously
Plant better species
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Shade Management

• Keep traffic off turf
• Remember compensation point!
• Build walkway
• Use fencing
• Broadleaf or non-living groundcovers
• Ivy, Lilies of the Valley, etc.
• Stone, bark mulch

Walkway protects shaded turf