WEED MANAGEMENT

FORESTED

WETLANDS

Weed Problems

• Early successional – let nature take its course

Florida Institute of Phosphate Research

• Invasive, persistent exotics – nature needs some help

Primrose Willow and Cattail

Florida Institute of Phosphate Research

• Considered as nuisance species by DEP

• Primrose willow a category I invasive according to FLEPPC

Reclaimed Forested Wetlands

Florida Institute of Phosphate Research

• Primrose willow, cattail and elderberry effects on wetland trees

• Can trees shade-out primrose, etc.?

• Consequences: let nature take its course vs. herbicides, mowing, etc.

Primrose Willow

Primrose Willow Mowed

Resprouted

Weeds Removed

Trees grow in the presence of primrose willow and overtop it

Tree canopy shades out primrose willow

Tree HeightMobil Canopy Site

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6

Year

Hei

ght (

cm)

Bald Cypress

Water Hickory

Popash

Primrose Willow

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

Year

Baldcypress

Water Hickory

Popash

Baldcypress

Water Hickory

PopashP

erc

en

t (%

)

Canopy Site

Trees Taller than Primrose Willow

Primrose Willow Leaf Area IndexTree Species Effects

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Baldcypress Popash Water Hickory

Tree Species

LA

I

4 Year

5 Year

6 Year

7 Year

Control (without Trees)

Leaf Area Index of Primrose WillowEffect of Trees

0

0.5

1

1.5

2

2.5

3

1998 1999

Years

Le

af

Are

a In

de

x

a

b

McCullough CreekCompetition

Bald Cypress, Red Maple, Popash Planted Nov. 1992, 2.1 m (7 ft) Spacing

Shade Tolerant Understory

With Primrose willow

Primrose willow removed: sun-loving weeds

Weed Removal and Possible Tree Damage

Pond Cypress and Cattail

Bald Cypress and Cattail

Tree Canopy Shades-Out Cattail

Tree Canopy Shades-Out Cattail

Hummocks and Understory Colonization

Reclaimed Forested WetlandsRole of Primrose Willow and Elderberry

Florida Institute of Phosphate Research

• Pioneer species (shaded out by trees)

• Organic matter and nutrient accumulation

• Early canopy closure (shade tolerant understory)

Forested WetlandsDealing with Primrose Willow and Cattail

Florida Institute of Phosphate Research

• Wetland trees grow in spite of these “nuisance” species

• Trees can shade them out

• Weed control efforts may damage trees• Early canopy closure (trees + primrose

willow) enhances understory

Trees Can Grow with and Shade-out Primrose Willow and Cattail

• Trees grow slower in ponded conditions

• Better growth if moist but well-drained– Seepage slope vs. flood plain vs. pond– Trees grow faster on primrose willow sites

than cattail sites

• Need sufficient tree density

• Need time and patience

Wetland Trees and Weeds

• Timber vs. Natural System Restoration• Popash & Red Maple growth better with

primrose willow than without (triclopyr sprayed around bagged trees)

• Bald Cypress has some tolerance to triclopyr• Tree growth better with elderberry than with

primrose willow• Organic matter accumulation less with weeds

removed (soil elevation difference)

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6Year

Hei

ght (

m)

Unweeded

Weeded

P1:Baldcypress

Figure 1. Yearly height of baldcypress as affected by primrose willow competition at Clear Springs site (P1)

Primrose Willow

0

20

40

60

80

100

0 1 2 3 4 5 6Year

Perc

ent T

rees

> 2

.7 m

P1: Baldcypress

Figure 2. Percentage of baldcypress trees taller than the primrose willow canopy (2.7 m) at Clear Springs site (P1)

Primrose willow effects on baldcypress heights

0

100

200

300

400

500

600

0 1 2 3 4 5 6Year

He

igh

t (c

m)

Unweeded

Weeded

Primrose Willow

Baldcypress - McCullough Creek

Primrose willow effects on red maple height

0.0

100.0

200.0

300.0

400.0

500.0

600.0

0 1 2 3 4 5 6Year

He

igh

t (c

m)

Straight

Straight & Bent

Weeded

Primrose Willow

Red Maple - McCullough Creek

Primrose willow effects on popash height

0

100

200

300

400

500

600

0 1 2 3 4 5 6

Year

He

igh

t (c

m)

Straight

Straight & Bent

Weeded

Primrose Willow

Popash - McCullough Creek

Elderberry and Primrose Willow Effects on Baldcypress Height

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8

Year

Hei

gh

t (m

)

ElderberryPrimrose Willow & ElderberryWeeded Control

Baldcypress

Rocky Branch

Elderberry and Primrose Willow Effects on Popash Height

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8

Year

Hei

gh

t (m

)

ElderberryPrimrose Willow & ElderberryWeeded Control

Popash

Rocky Branch

0

1

2

3

4

5

6

7

8

2 3 4 5 6 7 8 9 10 11 12

Year

Hei

gh

t (m

)

Unweeded

Weeded

Pondcypress (Planted 1992)

Cattail

0

1

2

3

4

5

6

7

8

2 3 4 5 6 7 8 9 10 11 12

Year

Hei

gh

t (m

)

Unweeded

Weeded

Baldcypress (Planted 1992)

Cattail

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8 9 10

Year

He

igh

t (m

)

Unweeded

Weeded

Baldcypress (Planted 1994)

Cattail

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 3 8 9 10

Year

He

igh

t (m

)

Unweeded

Weeded

Popash (Planted 1994)

Cattail

Water Depth Effects on Tree Heights (Year 3 Weeded Plots)

0

50

100

150

200

250

300

350

Clear Springs McCulloughCompetition

RockyBranch

Mobil Cattail Cargill Cattail

Study Site

Tre

e H

eig

ht

(cm

)

0

5

10

15

20

25

30

35

40

45

50

Wa

ter

De

pth

(c

m)

Baldcypress

Popash

Water Depth

Richardson, S.G., and R.A. Kluson. 2000. Managing nuisance plant species in forested wetlands on reclaimed phosphate mined lands in Florida, p. 104-118. In P.J. Cannizzaro (ed.). Proceedings of the 26th Annual Conference on Ecosystems Restoration and Creation. Hillsborough Community College, Tampa, Florida. May, 1999.

Reference